Journal articles on the topic 'Phytophthora cinnamomi control'
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1
Benson, D. M., and Frank A. Blazich. "Control of Phytophthora Root Rot of Rhododendron chapmanii A. Gray with Subdue." Journal of Environmental Horticulture 7, no. 2 (June 1, 1989): 73–75. http://dx.doi.org/10.24266/0738-2898-7.2.73.
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Abstract Rooted cuttings of Chapman's rhododendron (Rhododendron chapmanii) in soilless medium were challenged with inoculum of the soi1borne fungus, Phytophthora cinnamomi (Rands). A portion of the plants received a soil drench of Subdue 2EC (metalaxyl) at 0.16 ml/L (2.0 oz/100 gal) at 2 month intervals. Chapman's rhododendron was highly susceptible to P. cinnamomi, but five of six plants treated with Subdue did not develop symptoms of Phytophthora root rot. In the one plant which developed root rot symptoms, P. cinnamomi was recovered in culture.
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Downer, A. J., J. A. Menge, and E. Pond. "Association of Cellulytic Enzyme Activities in Eucalyptus Mulches with Biological Control of Phytophthora cinnamomi." Phytopathology® 91, no. 9 (September 2001): 847–55. http://dx.doi.org/10.1094/phyto.2001.91.9.847.
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A series of samples were taken from mulched and unmulched trees starting at the surface of mulch or soil to a 15 cm soil depth, forming a vertical transect. Saprophytic fungi isolated from the soil samples on rose bengal medium and surveyed visually were most abundant in mulches and at the interface of mulch and soil (P < 0.05). Microbial activity as assayed by the hydrolysis of fluorescein diacetate was significantly greater in mulch layers than in soils. Cellulase and laminarinase enzyme activities were greatest in upper mulch layers and rapidly decreased in soil layers (P < 0.05). Enzyme activities against Phytophthora cinnamomi cell walls were significantly greater in mulch than in soil layers. When Phytophthora cinnamomi was incubated in situ at the various transect depths, it was most frequently lysed at the interface between soil and mulch (P < 0.001). Roots that grew in mulch layers were significantly less infected with Phytophthora cinnamomi than roots formed in soil layers. In mulched soil, roots were commonly formed at the mulch-soil interface where Phytophthora populations were reduced, whereas roots in unmulched soil were numerous at the 7.5 cm depth where Phytophthora cinnamomi was prevalent. Enzyme activities were significantly and positively correlated with each other, microbial activity, and saprophytic fungal populations, but significantly and negatively correlated with Phytophthora recovery.
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Gastañadui, Paul, Rocío Moreno, Patricia Elena Quiroz-Delgado, and Walter Eduardo Apaza-Tapia. "Control of avocado root rot caused by Phytophthora cinnamomi with different Trichoderma strains at Chavimochic Irrigation Project." Peruvian Journal of Agronomy 5, no. 3 (December 30, 2021): 78–86. http://dx.doi.org/10.21704/pja.v5i3.1846.
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Avocado root rot caused by Phytophthora cinnamomi is one of the main problems affecting avocado (Persea americana) cultivation in Peru, especially at the Chavimochic Irrigation Project. The objective of this study was to evaluate the effect of different Trichoderma strains on the control of Phytophthora cinnamomi in Zutano rootstock under greenhouse conditions. Five isolates of Trichoderma were tested: Trichoderma sp. (Chav01); Trichoderma harzianum (Chavo2); Trichoderma harzianum (UNALM01); Trichoderma viride (UNALM02); and a commercial strain of Trichoderma sp. Evaluations were performed at 30, 45, and 60 days. All isolates colonized the rhizosphere of the avocado. No relation was found between the formation of more Trichoderma colonies and Phytophthora improved control. All strains controlled the root rot, but Chav01 and Chav02 showed the greatest diameter of stem, dry matter in the root, and percentage of healthy root in comparison with UNALM01, UNALM02, and the commercial strain. Thus, the native isolates of Trichoderma from the Chavimochic area can be added to the list of potential new Trichoderma species to control Phytophthora cinnamomi.
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Alvarado, Laureano, Sebastián Saa, Italo F. Cuneo, Romina Pedreschi, Javiera Morales, Alejandra Larach, Wilson Barros, Jeannette Guajardo, and Ximena Besoain. "A Comparison of Immediate and Short-Term Defensive Responses to Phytophthora Species Infection in Both Susceptible and Resistant Walnut Rootstocks." Plant Disease 104, no. 3 (March 2020): 921–29. http://dx.doi.org/10.1094/pdis-03-19-0455-re.
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Clonal rootstocks are one alternative used by the walnut industry to control damage caused by Phytophthora species, traditionally using plants grafted on susceptible Juglans regia rootstock. Vlach, VX211, and RX1 are clonal rootstocks with a degree of resistance to Phytophthora species. The resistance to pathogens in these rootstocks depends on the resistance mechanisms activated by the presence of the pathogen and subsequent development of responses in the host. In this work, we analyzed how plants of J. regia, Vlach, VX211, and RX1 responded to inoculation with Phytophthora cinnamomi or Phytophthora citrophthora isolates obtained from diseased English walnut plants from Chilean orchards. After inoculation, plants of Vlach, VX211, and RX1 showed canopy and root damage indexes that did not differ from noninoculated control plants. In contrast, plants of J. regia, which is susceptible to P. cinnamomi and P. citrophthora, died after inoculation. Vlach, VX211, and RX1 plants inoculated with P. cinnamomi or P. citrophthora showed greater root weight and volume and greater root growth rates than their respective controls. These results suggest that short-term carbohydrate dynamics may be related to the defense mechanisms of plants; they are immediately activated after inoculation through the production of phenolic compounds, which support the further growth and development of roots in walnut clonal rootstocks. To our knowledge, this is the first study that comprehensively characterizes vegetative and radicular growth and the dynamics of sugars and phenols in response to infection with P. cinnamomi or P. citrophthora in walnut rootstocks.
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Andrade-Hoyos, Petra, Omar Romero-Arenas, Hilda Victoria Silva-Rojas, Alfonso Luna-Cruz, José Espinoza-Pérez, Aarón Mendieta-Moctezuma, and José Alberto Urrieta-Velázquez. "Cinnamom verum Plantations in the Lowland Tropical Forest of Mexico Are Affected by Phytophthora cinnamomi, Phylogenetically Classified into Phytophthora Subclade 7c." Horticulturae 9, no. 2 (February 2, 2023): 187. http://dx.doi.org/10.3390/horticulturae9020187.
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Cinnamon is a tree introduced to the lowlands of Mexico in the mid-16th century, but it spread to other places at the beginning of the 20th century due to its important commercial value as an aromatic spice. In the state of Veracruz, symptoms of dieback have been observed in 12-year-old cinnamon plantations cultivated in an agroforestry system, causing concern among producers. For this reason, the present investigation was carried out to determine the causal agent of these symptoms observed in cinnamon trees. Fifty symptomatic plants were recovered from established plantations. One hundred cinnamon root fragments showing dieback were selected and separated; isolates were made from tissue showing crown and root rot on clarified juice V-8 agar medium. After eight days, the growth of whitish coralloid mycelium with characteristics similar to the Phytophthora oomycete was consistently observed. Subsequently, the identity corresponding to P. cinnamomi was confirmed by morphological, taxonomic studies and Bayesian inference of the rDNA internal transcribed spacer. The pathogenicity test was performed on 20 6-month-old cinnamon plants grown in pots by inoculating 2.5 × 104/mL of zoospores around the roots. Control plants were inoculated with sterile distilled water and kept in a greenhouse under conditions controlled. After five weeks, symptoms of root rot were observed in the inoculated plants; however, the control group plants remained healthy. The results showed that P. cinnamomi subclade 7c was responsible for the symptoms observed in lowland cinnamon plantations in Mexico. Our findings suggest that this phytopathogen is a new threat for cinnamon growers; likewise, it is recommended that growers implement management strategies to avoid its introduction into nurseries or new plantations that could be susceptible to this pathogen.
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Agapito Amador, María Eugenia, Víctor David Cibrián-Llanderal, Mónica Gutiérrez Rojas, Daniel Ruiz-Juárez, Betzabe Ebenhezer López Corona, and Edgar Omar Rueda-Puente. "Phytophthora cinnamomi Rands en aguacate." Revista Mexicana de Ciencias Agrícolas, no. 28 (September 22, 2022): 331–41. http://dx.doi.org/10.29312/remexca.v13i28.3287.
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El objetivo de la presente revisión es dar a conocer el estatus epidemiológico de Phytophthora cinnamomi Rands en interacción con Persea americana Mill. y las alternativas de manejo fitosanitario autorizadas. El ensayo se realizó con base en reportes de instancias oficiales y científicas en materia de sanidad vegetal, de brotes epidemiológicos de la enfermedad tristeza del aguacate causada por P. cinnamomi. A nivel mundial, la pérdida de árboles de aguacate fue exponencial, debido a la enfermedad causada por el oomiceto P. cinnamomi quien presentó comportamiento epidemiológico a nivel nacional e internacional. En 1942, en Puerto Rico el patógeno fue aislado por primera vez por Tucker en plantas de aguacate. En México, el primer brote epidemiológico por este patógeno fue en 1952, con pérdidas de 90% de la producción de aguacate, la distribución de la enfermedad se expandió a diferentes partes del mundo. En condiciones favorables afecta la raíz y base de la corona, invade haces vasculares y toma los nutrientes para su desarrollo. La patogénesis es influenciada por la temperatura, precipitación, humedad, pH, disponibilidad de nutrientes y textura del suelo. En campo, la efectividad biológica de las moléculas, para el control del oomiceto, puede presentar limitantes que impactan en la microbiota, flora y fauna; además, de los efectos que se reflejan en la calidad e inocuidad de frutos por la acumulación de moléculas de plaguicidas sintéticos. Dada la situación fitosanitaria que expresa la producción de aguacate es necesario implementar alternativas de manejo sustentable, como la endoterapia, a través de la inyección de productos selectivos en dosis específicas, que controlen a la enfermedad sin afectar la calidad e inocuidad del fruto.
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Sumida, Ciro Hideki, Lucas Henrique Fantin, Karla Braga, Marcelo Giovanetti Canteri, and Martin Homechin. "Control of root rot (Phytophthora cinnamomi) in avocado (Persea Americana) with bioagents." Summa Phytopathologica 46, no. 3 (September 2020): 205–11. http://dx.doi.org/10.1590/0100-5405/192195.
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ABSTRACT Despite the favorable edaphoclimatic conditions for avocado production in Brazil, diseases such as root rot caused by the pathogen Phytophthora cinnamomi compromise the crop. With the aim of managing root rot in avocado, the present study aimed to evaluate chemical and biological control with isolates of Trichoderma spp. and Pseudomonas fluorescens. Thus, three assays were conducted to assess: (i) mycelial inhibition of P. cinnamomi by isolates of Trichoderma spp. and P. fluorescens from different crop systems; (ii) effect of autoclaved and non-autoclaved metabolites of P. fluorescens, and (iii) chemical or biological treatment of avocado seedlings on the control of root rot under field conditions. The isolates of Trichoderma spp. from maize cultivation soil and the commercial products formulated with Trichoderma presented greater antagonism (p <0.05) to the pathogen P. cinnamomi in the in vitro tests. Similarly, non-autoclaved metabolites of P. fluorescens presented antagonistic potential to control P. cinnamomi. Under field conditions, the fungicide metalaxyl and the bioagents showed effectiveness in controlling P. cinnamomi, as well as greater root length and mass. Results demonstrated potential for the biological control of avocado root rot with Trichoderma spp. and P. fluorescens.
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Saiz-Fernández, Iñigo, Ivan Milenković, Miroslav Berka, Martin Černý, Michal Tomšovský, Břetislav Brzobohatý, and Pavel Kerchev. "Integrated Proteomic and Metabolomic Profiling of Phytophthora cinnamomi Attack on Sweet Chestnut (Castanea sativa) Reveals Distinct Molecular Reprogramming Proximal to the Infection Site and Away from It." International Journal of Molecular Sciences 21, no. 22 (November 12, 2020): 8525. http://dx.doi.org/10.3390/ijms21228525.
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Phytophthora cinnamomi is one of the most invasive tree pathogens that devastates wild and cultivated forests. Due to its wide host range, knowledge of the infection process at the molecular level is lacking for most of its tree hosts. To expand the repertoire of studied Phytophthora–woody plant interactions and identify molecular mechanisms that can facilitate discovery of novel ways to control its spread and damaging effects, we focused on the interaction between P. cinnamomi and sweet chestnut (Castanea sativa), an economically important tree for the wood processing industry. By using a combination of proteomics, metabolomics, and targeted hormonal analysis, we mapped the effects of P. cinnamomi attack on stem tissues immediately bordering the infection site and away from it. P. cinnamomi led to a massive reprogramming of the chestnut proteome and accumulation of the stress-related hormones salicylic acid (SA) and jasmonic acid (JA), indicating that stem inoculation can be used as an easily accessible model system to identify novel molecular players in P. cinnamomi pathogenicity.
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D'Souza, Nola K., Ian J. Colquhoun, Bryan L. Shearer, and Giles E. St J. Hardy. "The potential of five Western Australian native Acacia species for biological control of Phytophthora cinnamomi." Australian Journal of Botany 52, no. 2 (2004): 267. http://dx.doi.org/10.1071/bt03089.
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Five Acacia species native to Western Australia were assessed for their potential to protect the highly susceptible species Banksia grandis Wield from infection by the plant pathogen Phytophthora cinnamomi Rands. In a rehabilitated bauxite pit at Jarrahdale 55 km south-east of Perth and in a glasshouse trial, B. grandis planted either alone or with A. pulchella R.Br., A. urophylla Benth., A. extensa Lindl., A. lateriticola Maslin or A. drummondii Lindl., was soil inoculated with P. cinnamomi. It could only be shown that A. pulchella significantly protected B. grandis from P. cinnamomi infection in the rehabilitated bauxite pit trial up to 1 year after inoculation. This confirms the potential of this species for biological control of the pathogen in infested plant communities. The observed protection was not the result of a decrease in soil temperature or moisture. Protection was not emulated in a glasshouse trial where optimum environmental conditions favoured P. cinnamomi. Despite a delay in infection of B. grandis planted with Acacia spp., none of the five species definitively protected B. grandis from P. cinnamomi. However, in the glasshouse trial, A. pulchella, A. extensa, A. lateriticola and A. drummondii did significantly reduce the soil inoculum of P. cinnamomi, indicating a possible biological control effect on the pathogen. The mechanisms of biological control are discussed and the implications for management of rehabilitated bauxite mined areas and forests severely affected by P. cinnamomi are considered.
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Onsando, J. M., and C. N. Gathungu. "CONTROL OF AVOCADO ROOT ROT CAUSED BY PHYTOPHTHORA CINNAMOMI." Acta Horticulturae, no. 218 (January 1988): 351–54. http://dx.doi.org/10.17660/actahortic.1988.218.45.
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Weiland, Jerry E., Carolyn F. Scagel, Niklaus J. Grünwald, E. Anne Davis, Bryan R. Beck, and Val J. Fieland. "Variation in Disease Severity Caused by Phytophthora cinnamomi, P. plurivora, and Pythium cryptoirregulare on Two Rhododendron Cultivars." Plant Disease 102, no. 12 (December 2018): 2560–70. http://dx.doi.org/10.1094/pdis-04-18-0666-re.
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Rhododendrons are an important crop in the ornamental nursery industry, but are prone to Phytophthora root rot. Phytophthora root rot is a continuing issue on rhododendrons despite decades of research. Several Phytophthora species are known to cause root rot, but most research has focused on P. cinnamomi, and comparative information on pathogenicity is limited for other commonly encountered oomycetes, including Phytophthora plurivora and Pythium cryptoirregulare. In this study, three isolates each of P. cinnamomi, P. plurivora, and Py. cryptoirregulare were used to inoculate rhododendron cultivars Cunningham’s White and Yaku Princess at two different inoculum levels. All three species caused disease, especially at the higher inoculum level. P. cinnamomi and P. plurivora were the most aggressive pathogens, causing severe root rot, whereas Py. cryptoirregulare was a weak pathogen that only caused mild disease. Within each pathogen species, isolate had no influence on disease. Both P. cinnamomi and P. plurivora caused more severe disease on Cunningham’s White than on Yaku Princess, suggesting that the relative resistance and susceptibility among rhododendron cultivars might be similar for both pathogens. Reisolation of P. cinnamomi and P. plurivora was also greater from plants exhibiting aboveground symptoms of wilting and plant death and belowground symptoms of root rot than from those without symptoms. Results show that both P. cinnamomi and P. plurivora, but not Py. cryptoirregulare, are important pathogens causing severe root rot in rhododendron. This study establishes the risks for disease resulting from low and high levels of inoculum for each pathogen. Further research is needed to evaluate longer term risks associated with low inoculum levels on rhododendron health and to explore whether differences among pathogen species affect disease control.
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El-Tarabily, Khaled A., Melissa L. Sykes, Ipek D. Kurtböke, Giles E. St J. Hardy, Aneli M. Barbosa, and Robert F. H. Dekker. "Synergistic effects of a cellulase-producing Micromonospora carbonacea and an antibiotic-producing Streptomyces violascens on the suppression of Phytophthora cinnamomi root rot of Banksia grandis." Canadian Journal of Botany 74, no. 4 (April 1, 1996): 618–24. http://dx.doi.org/10.1139/b96-078.
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Three polyvalent Streptomyces phages were used to isolate four Micromonospora species (M. carbonacea, M. chalcea, M. purpureochromogenes, and M. inositola) from mine-site rhizosphere soils in Western Australia. Streptomyces violascens was isolated using selective isolation techniques from the same soils. The Micromonspora spp. were examined for their ability to produce cellulases. Micromonospora carbonacea, M. chalcea, and M. purpureochromogenes, which were found to produce the enzyme, caused lysis of Phytophthora cinnamomi hyphae. Glasshouse trials showed that the use of the cellulase-producing M. carbonacea isolate, in conjunction with the antibiotic-producing S. violascens isolate, had a synergistic effect on the suppression of the Phytophthora root rot and in promoting growth of Banksia grandis. The importance of using a number of antagonists with different antagonistic abilities to control plant pathogenic fungi is discussed. Keywords: biological control, Micromonospora carbonacea, Streptomyces violascens, cellulases, Phytophthora cinnamomi.
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Ruiz-Gómez, Francisco J., and Cristina Miguel-Rojas. "Antagonistic Potential of Native Trichoderma spp. against Phytophthora cinnamomi in the Control of Holm Oak Decline in Dehesas Ecosystems." Forests 12, no. 7 (July 17, 2021): 945. http://dx.doi.org/10.3390/f12070945.
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Phytophthora root rot caused by the pathogen Phytophthora cinnamomi is one of the main causes of oak mortality in Mediterranean open woodlands, the so-called dehesas. Disease control is challenging; therefore, new alternative measures are needed. This study focused on searching for natural biocontrol agents with the aim of developing integrated pest management (IPM) strategies in dehesas as a part of adaptive forest management (AFM) strategies. Native Trichoderma spp. were selectively isolated from healthy trees growing in damaged areas by P. cinnamomi root rot, using Rose Bengal selective medium. All Trichoderma (n = 95) isolates were evaluated against P. cinnamomi by mycelial growth inhibition (MGI). Forty-three isolates presented an MGI higher than 60%. Twenty-one isolates belonging to the highest categories of MGI were molecularly identified as T. gamsii, T. viridarium, T. hamatum, T. olivascens, T. virens, T. paraviridescens, T. linzhiense, T. hirsutum, T. samuelsii, and T. harzianum. Amongst the identified strains, 10 outstanding Trichoderma isolates were tested for mycoparasitism, showing values on a scale ranging from 3 to 4. As far as we know, this is the first report referring to the antagonistic activity of native Trichoderma spp. over P. cinnamomi strains cohabiting in the same infected dehesas. The analysis of the tree health status and MGI suggest that the presence of Trichoderma spp. might diminish or even avoid the development of P. cinnamomi, protecting trees from the worst effects of P. cinnamomi root rot.
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Hu, Jiahuai, Chuanxue Hong, Erik L. Stromberg, and Gary W. Moorman. "Mefenoxam Sensitivity in Phytophthora cinnamomi Isolates." Plant Disease 94, no. 1 (January 2010): 39–44. http://dx.doi.org/10.1094/pdis-94-1-0039.
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Phytophthora cinnamomi is a destructive root pathogen of numerous woody plant species in the ornamental plant nursery. Sixty-five isolates of P. cinnamomi were evaluated for mefenoxam sensitivity on 20% clarified V8 agar amended with mefenoxam at 0 or 100 μg/ml. In the presence of mefenoxam at 100 μg/ml, eight isolates were intermediately sensitive, with mycelium growth ranging between 11 and 18% of the nonamended control, and 57 isolates were highly sensitive, with little or no mycelium growth. Five intermediately sensitive and five sensitive isolates were chosen to characterize their responses to mefenoxam at 0, 0.1, 1, 10, and 100 μg/ml. For intermediately sensitive isolates, the mefenoxam concentration causing 50% inhibition of mycelium growth (EC50 values) ranged between 0.03 and 0.08 μg/ml; EC50 values for sensitive isolates varied from 0.01 to 0.02 μg/ml. Five intermediately sensitive and seven sensitive isolates were selected further to assess in vivo sensitivity to mefenoxam using Lupinus angustifolius ‘Russell Hybrids’. Lupine seedlings were treated with distilled water or mefenoxam at label rate (Subdue MAXX, 1 fl. oz. of product per 100 gal.) and then, 2 days later, inoculated with a 5-mm-diameter mycelial plug of P. cinnamomi on each cotyledon. Mefenoxam-treated plants averaged more than 96% less disease than water-treated plants. Mefenoxam provided adequate protection of lupines from infection by all 12 isolates regardless of their in vitro levels of sensitivity to mefenoxam. The ability to develop mefenoxam resistance was assessed in P. cinnamomi isolates with different mefenoxam sensitivity by UV mutagenesis and adapting mycelium to increasing concentrations of mefenoxam. Both UV mutagenesis and mycelium adaptation generated isolates with reduced sensitivity to mefenoxam. These isolates, however, did not grow as quickly as their corresponding parent. This study suggests that P. cinnamomi populations from ornamental nurseries in Virginia are sensitive to mefenoxam.
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Longmuir, Amy L., Peter L. Beech, and Mark F. Richardson. "Draft genomes of two Australian strains of the plant pathogen, Phytophthora cinnamomi." F1000Research 6 (November 8, 2017): 1972. http://dx.doi.org/10.12688/f1000research.12867.1.
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Background: The oomycete plant pathogen, Phytophthora cinnamomi, is responsible for the destruction of thousands of species of native Australian plants, as well as several crops, such as avocado and macadamia, and has one of the widest host-plant ranges of the Phytophthora genus. The currently available genome of P. cinnamomi is based on an atypical strain and has large gaps in its assembly. To further studies of the pathogenicity of this species, especially in Australia, more robust assemblies of the genomes of more typical strains are required. Here we report the genome sequencing, draft assembly, and preliminary annotation of two geographically separated Australian strains of P. cinnamomi. Findings: Some 308 million raw reads were generated for the two strains. Independent genome assembly produced final genomes of 62.8 Mb (in 14,268 scaffolds) and 68.1 Mb (in 10,084 scaffolds), which are comparable in size and contiguity to other Phytophthora genomes. Gene prediction yielded > 22,000 predicted protein-encoding genes within each genome, while BUSCO assessment showed 82.5% and 81.8% of the eukaryote universal single-copy orthologs to be present in the assembled genomes, respectively. Conclusions: The assembled genomes of two geographically distant isolates of Phytophthora cinnamomi will provide a valuable resource for further comparative analysis and evolutionary studies of this destructive pathogen, and further annotation of the presented genomes may yield possible targets for novel pathogen control methods.
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Longmuir, Amy L., Peter L. Beech, and Mark F. Richardson. "Draft genomes of two Australian strains of the plant pathogen, Phytophthora cinnamomi." F1000Research 6 (February 28, 2018): 1972. http://dx.doi.org/10.12688/f1000research.12867.2.
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Background: The oomycete plant pathogen, Phytophthora cinnamomi, is responsible for the destruction of thousands of species of native Australian plants, as well as several crops, such as avocado and macadamia, and has one of the widest host-plant ranges of the Phytophthora genus. The current reference genome of P. cinnamomi is based on an atypical strain and has large gaps in its assembly. To further studies of the pathogenicity of this species, especially in Australia, robust genome assemblies of more typical strains are required. Here we report the genome sequencing, draft assembly, and preliminary annotation of two geographically separated Australian strains of P. cinnamomi. Findings: Some 308 million raw reads were generated for the two strains, DU054 and WA94.26. Independent genome assembly produced final genome sequences of 62.8 Mb (in 14,268 scaffolds) and 68.1 Mb (in 10,084 scaffolds), which are comparable in size and contiguity to other Phytophthora genomes. Gene prediction yielded > 22,000 predicted protein-encoding genes within each genome, while BUSCO assessment showed 94.4% and 91.5% of the stramenopile single-copy orthologs to be present in the assembled genomes, respectively. Conclusions: The assembled genomes of two geographically distant isolates of Phytophthora cinnamomi will provide a valuable resource for further comparative analyses and evolutionary studies of this destructive pathogen, and further annotation of the presented genomes may yield possible targets for novel pathogen control methods.
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Meadows, I. M., D. C. Zwart, S. N. Jeffers, T. A. Waldrop, and W. C. Bridges. "Effects of Fuel Reduction Treatments on Incidence of Phytophthora Species in Soil of a Southern Appalachian Mountain Forest." Plant Disease 95, no. 7 (July 2011): 811–20. http://dx.doi.org/10.1094/pdis-07-10-0505.
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The National Fire and Fire Surrogate Study was initiated to study the effects of fuel reduction treatments on forest ecosystems. Four fuel reduction treatments were applied to three sites in a southern Appalachian Mountain forest in western North Carolina: prescribed burning, mechanical fuel reduction, mechanical fuel reduction followed by prescribed burning, and a nontreated control. To determine the effects of fuel reduction treatments on Phytophthora spp. in soil, incidences were assessed once before and twice after fuel reduction treatments were applied. Also, the efficiency of the baiting bioassay used to detect species of Phytophthora was evaluated, and the potential virulence of isolates of Phytophthora spp. collected from forest soils was determined. Phytophthora cinnamomi and P. heveae were the only two species recovered from the study site. Incidences of these species were not significantly affected by fuel reduction treatments, but incidence of P. cinnamomi increased over time. In the baiting bioassay, camellia leaf disks were better than hemlock needles as baits. P. cinnamomi was detected best in fresh soil, whereas P. heveae was detected best when soil was air-dried and remoistened prior to baiting. Isolates of P. heveae were weakly virulent and, therefore, potentially pathogenic—causing lesions only on wounded mountain laurel and rhododendron leaves; however, isolates of P. cinnamomi were virulent and caused root rot and mortality on mountain laurel and white pine plants.
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Casonato, S. G., M. A. Manning, P. A. Rheinlander, and R. A. Fullerton. "Control of Phytophthora cinnamomi in Erica sessiliflora and Erica davisii." New Zealand Plant Protection 61 (August 1, 2008): 86–90. http://dx.doi.org/10.30843/nzpp.2008.61.6823.
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A field trial was conducted to test the efficacy of two fungicides (metalaxyl and phosphorous acid) and supplementary organic matter for the control of Phytophthora cinnamomi root rot in Erica sessiliflora and E davisii Five treatments were applied (1) untreated control (2) metalaxyl (3) phosphorous acid (4) metalaxyl plus phosphorous acid and (5) organic soil amendment Plants were assessed for plant health as an indication of possible P cinnamomi infection Phosphorous acid applied alone or in combination with metalaxyl resulted in a significant reduction in the number of diseased or dead E sessiliflora plants compared with the untreated control plants (P0011 and P0004 respectively) The mean health index of phosphorous acid treated E davisii plants was not different (P>005) to control plants Results suggest that this species of Erica has some tolerance to P cinnamomi Metalaxyl applications alone or organic matter treatments did not reduce disease relative to controls in either species
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Ochoa Fuentes, Yisa María, Anselmo Hernández Pérez, Juan Carlos Delgado Ortiz, Ernesto Cerna Chavez, Luis Alberto Aguirre Uribe, and Luis Mario Tapia-Vargas. "Control orgánico in vitro de Phytophthora cinnamomi con aceites esenciales de orégano y clavo." Revista Mexicana de Ciencias Agrícolas 10, no. 4 (June 24, 2019): 961–68. http://dx.doi.org/10.29312/remexca.v10i4.1739.
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Michoacán es el principal estado productor de aguacate en el mundo; sin embargo, las enfermedades radiculares diezman y dañan los árboles ocasionando su muerte. El objetivo de la presente investigación fue evaluar el control orgánico del crecimiento in vitro de Phytophthora cinnamomi con aceites esenciales de orégano (Lippia berlandieri) y clavo (Syzygium aromaticum). En los meses de octubre y noviembre de 2016, se recolectaron muestras de raíces en árboles con síntomas de la enfermedad en aguacate (Persea americana Mill. var. Hass), en la huerta experimental del INIFAP ubicada en San Juan Nuevo Parangaricutiro, Michoacán. Los aislados se identificaron morfológica y molecularmente. Se evaluó el control de P. cinnamomi con aceites esenciales de orégano y clavo determinando la concentración media inhibitoria y sus límites fiduciales al 95% mediante una regresión Probit por el método de máximas verosimilitud. Los análisis se realizaron utilizando el programa estadístico R 3.4. De acuerdo con los resultados obtenidos, en relación con la inhibición del crecimiento hay una reducción en el crecimiento de P. cinnamomi. Los aceites esenciales de clavo (Syzygium aromaticum) y orégano (Lippia berlandieri) son una alternativa natural para el control del oomiceto P. cinnamomi por su actividad fungicida a bajas concentraciones y pueden incluirse en programas de manejo integrado de enfermedades.
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Miranda-Fontaíña, M. E., J. Fernández-López, A. M. Vettraino, and A. Vannini. "Resistance of Castanea Clones to Phytophthora Cinnamomi: Testing and Genetic Control." Silvae Genetica 56, no. 1-6 (December 1, 2007): 11–21. http://dx.doi.org/10.1515/sg-2007-0002.
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Summary The resistance of chestnut clones to Phytophthora cinnamomi was evaluated by a soil inoculation experiment under controlled environmental conditions, as well as by excised and intact stem tests. One-year-old plants of fifty different clones were inoculated with two isolates of Phytophthora cinnamomi and evaluated fourteen weeks after inoculation. There were significant differences among clones for all root and collar rot variables. There were significant differences for isolates of P. cinnamomi but only for the collar rot variables. A total of 84% of plants grown in infested soil showed symptoms of root rot but only 50% of the plants with root rot, showed also had collar rot. The roots of resistant clones were able to confine the colonization, in roots and from roots to collar. Percentage circumference of collar rot was the best indicator or descriptor of sensitivity, a 50% of clones were resistant or highly resistant clones, with respectively less than 20% and than 10% circumference of collar rot. Percentage of survival of plants is not sufficient to indicate resistance to the pathogen, as mortality may be affected by environmental conditions or by other pathogens. The clonal heritability of collar rot variables ranged between 0.54 and 0.71. The plants grown on inoculated soil showed a reduction in growth. The phenotypic and genotypic correlations between soil infestation characteristics and the length of necrosis in both intact and excised stem tests were positive and highly significant and indicated similar resistance rankings of the clones.
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Downer, A. J., J. A. Menge, and E. Pond. "Effects of Cellulytic Enzymes on Phytophthora cinnamomi." Phytopathology® 91, no. 9 (September 2001): 839–46. http://dx.doi.org/10.1094/phyto.2001.91.9.839.
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Two enzyme systems, cellulase (β-1,4-glucanase) and laminarinase (β-1,3-glucanase), were added to soil extracts to simulate (in vitro) lytic components found in mulches suppressive to Phytophthora cinnamomi. Concentration ranges of each enzyme were incubated with Phytophthora cinnamomi mycelium, zoospores, zoospores cysts, and zoospore-infected excised roots to evaluate the roles of each enzyme in potential control of avocado root rot disease. Cellulase significantly retarded the development of zoosporangia and chlamydospores when mycelia were incubated in soil extract containing the enzyme at concentrations greater than 10 units/ml. Zoospore production was also reduced by cellulase but not by laminarinase. Laminarinase had little effect on zoosporangia or chlamydospore formation. At high concentrations, laminarinase was consistently more effective at preventing encystment than cellulase. Chlamydospores preformed in root tips were immune to the lytic effects of all treatments except cellulase at 100 units/ml. Zoospores placed in enzyme solutions and plated on a selective medium survived high cellulase concentrations and formed colonies, but there were fewer surviving zoospores when laminarinase was present at greater than 10 units/ml. Low concentrations of cellulase stimulated infection of excised roots, however, low concentrations of laminarinase prevented infection. Cellulase and laminarinase have different effects on the structures of the Phytophthora cinnamomi life history, however, each enzyme may have a role in reduction of inoculum.
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Scott, P. M., P. A. Barber, and G. E. St J. Hardy. "Novel phosphite and nutrient application to control Phytophthora cinnamomi disease." Australasian Plant Pathology 44, no. 4 (July 2015): 431–36. http://dx.doi.org/10.1007/s13313-015-0365-4.
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Tynan, K. M., C. J. Wilkinson, J. M. Holmes, B. Dell, I. J. Colquhoun, J. A. McComb, and G. E. St J. Hardy. "The long-term ability of phosphite to control Phytophthora cinnamomi in two native plant communities of Western Australia." Australian Journal of Botany 49, no. 6 (2001): 761. http://dx.doi.org/10.1071/bt00062.
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This study examined the ability of foliar applications of the fungicide phosphite to contain colonisation of Phytophthora cinnamomi in a range of plant species growing in natural plant communities in the northern sandplain and jarrah (Eucalyptus marginata) forest of south-western Australia. Wound inoculation of plant stems with P. cinnamomi was used to determine the efficacy of phosphite over time after application. Colonisation by P. cinnamomi was reduced for 5–24 months after phosphite was applied, depending on the concentration of phosphite used, plant species treated and the time of phosphite application. Plant species within and between plant communities varied considerably in their ability to take up and retain phosphite in inoculated stems and in the in planta concentrations of phosphite required to contain P. cinnamomi. As spray application rates of phosphite increased from 5 to 20 g L–1, stem tissue concentrations increased, as did the ability of a plant species to contain P. cinnamomi. However, at application rates of phosphite above 5 g L–1 phytotoxicity symptoms were obvious in most species, with some plants being killed. So, despite 10 and 20 g L–1 of phosphite being more effective and persistent in controlling P. cinnamomi, these rates are not recommended for application to the plant species studied. The results of this study indicate that foliar application of phosphite has considerable potential in reducing the impact of P. cinnamomi in native plant communities in the short-term. However, in order to maintain adequate control, phosphite should be sprayed every 6–12 months, depending on the species and/or plant community.
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Andrade-Hoyos, Petra, Hilda Victoria Silva-Rojas, and Omar Romero-Arenas. "Endophytic Trichoderma Species Isolated from Persea americana and Cinnamomum verum Roots Reduce Symptoms Caused by Phytophthora cinnamomi in Avocado." Plants 9, no. 9 (September 17, 2020): 1220. http://dx.doi.org/10.3390/plants9091220.
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Avocado root rot caused by the oomycete Phytophthora cinnamomi is a severe disease that affects avocado production in Mexico and worldwide. The use of biological control agents such as Trichoderma species isolated from places where the disease is always present, represents an efficient alternative to reduce losses. Thus, the objective of this research was to evaluate the biocontrol ability of 10 endophytic Trichoderma spp. strains against P. cinnamomi tested both in vitro and in the greenhouse. The endophytic Trichoderma spp. were recovered from Persea americana and Cinnamomum verum roots, isolated and purified on potato–dextrose–agar medium. Ten strains were identified by phylogenetic reconstruction of the internal transcribed spacer region of rDNA sequences as T. asperellum (T-AS1, T-AS2, T-AS6, and T-AS7), T. harzianum (T-H3, T-H4, and T-H5), T. hamatum (T-A12), T. koningiopsis (T-K8 and T-K11), and P. cinnamomi (CPO-PCU). In vitro dual-culture assay, the percentage of inhibition of radial growth (PIRG) between Trichoderma spp. and P. cinnamomi strains was measured according to the Bell’s scale. PIRG results indicated that T-AS2 reached the highest value of 78.32%, and T-H5 reached the lowest value of 38.66%. In the greenhouse, the infection was evaluated according to the percentage of disease incidence. Plants with the lowest incidence of dead by avocado root rot were those whose seedlings were inoculated with T-AS2 and T-AS7, resulting in only 5% death by root rot caused by P. cinnamomi. The disease incidence of seedlings with wilt symptoms and death decreased more than 50% in the presence of Trichoderma spp. Relying on the results, we conclude that T. asperellum and T. harzianum contribute to the biocontrol of soil-borne pathogenic oomycete P. cinnamomi.
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Morales-Rodríguez, C., A. M. Vettraino, and A. Vannini. "Efficacy of Biofumigation with Brassica carinata Commercial Pellets (BioFence) to Control Vegetative and Reproductive Structures of Phytophthora cinnamomi." Plant Disease 100, no. 2 (February 2016): 324–30. http://dx.doi.org/10.1094/pdis-03-15-0245-re.
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The efficacy of biofumigation with Brassica carinata pellets (BioFence) to control vegetative and reproductive structures of Phytophthora cinnamomi was investigated in vitro at different doses and temperatures. Biofumigation was effective in inhibiting mycelial growth (culture diameter) and chlamydospore and zoospore germination, and was lethal at 24 mg of pellet per plate (approximately 0.4 mg/liter). The 50% effective concentration values showed that efficacy of B. carinata pellets in inhibiting or killing the vegetative and reproductive structures of P. cinnamomi was maximum at 15°C and decreased as temperature rose to 25°C. However, the fungicide effect was independent of the temperature. In vivo biofumigation of Quercus cerris seedlings with BioFence confirmed efficacy by reducing the inoculum density (CFU/g) of P. cinnamomi, thus protecting the host from root infection. The use of BioFence provides an alternative to synthetic pesticides to control P. cinnamomi within disease management programs in agroforestry systems.
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Morales, Javiera, Ximena Besoain, Italo F. Cuneo, Alejandra Larach, Laureano Alvarado, Alejandro Cáceres-Mella, and Sebastian Saa. "Impact of Nitrogen Fertilization on Phytophthora cinnamomi Root-related Damage in Juglans regia Saplings." HortScience 54, no. 12 (December 2019): 2188–94. http://dx.doi.org/10.21273/hortsci14299-19.
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Excessive nitrogen (N) use in agriculture has been associated with increased severity of the damage caused by Phytophthora species. In this study, we investigated the impact in vitro and in vivo of N about Phytophthora cinnamomi. The preliminary in vitro assay showed the effect of different N sources on the mycelial growth of P. cinnamomi. This assay indicated that ammonium nitrate (NH4NO3) and ammonium sulfate [(NH4)2SO4] allowed for greater control of P. cinnamomi mycelia in comparison with calcium nitrate [Ca(NO3)2] and potassium nitrate (KNO3) when used with 1000 ppm N. The in vivo assay showed the severity of P. cinnamomi in 5-month-old Juglans regia saplings grown under greenhouse conditions. We selected NH4NH3 as the source for N for the greenhouse assay, considering the inhibitory effect on the ingrowth of P. cinnamomi and the intensive use of this fertilizer in agriculture. Walnut saplings were fertilized with 0, 35, 70, 140, 210, and 1050 ppm N and were inoculated with zoospores of P. cinnamomi 45 d after the application of nitrogen treatment (DAA). They were harvested at 90 DAA. We found that a 70-ppm N fertilization reduced the development of P. cinnamomi, resulting in lower root and canopy damage indices (DIs) than the unfertilized inoculated treatments and fertilized treatments greater than 140 ppm. The results of the in vitro and in vivo assay agree that increased N concentrations were associated with reduced mycelium growth of P. cinnamomi, providing further evidence that N fertilization can mitigate this disease. Greater root and canopy damage was observed in saplings fertilized with 1050 ppm N, regardless of whether they were inoculated with P. cinnamomi, as a result of N phytotoxicity (verified through foliar analysis). In contrast, inoculated and unfertilized saplings (N0) also showed high root and canopy DIs associated either with the inoculation with P. cinnamomi or the no fertilization treatment. We postulate that 70 ppm N is the best fertilization rate for J. regia saplings because the positive effects of N on growth are maximized and the damage caused by P. cinnamomi is mitigated.
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Qiu, Rui, Dong Qu, Robert Trengove, Manjree Agarwal, Giles E. St J. Hardy, and Yonglin Ren. "Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry for Analysis of VOCs Produced by Phytophthora cinnamomi." Plant Disease 98, no. 8 (August 2014): 1099–105. http://dx.doi.org/10.1094/pdis-01-14-0049-re.
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Volatile organic compounds (VOCs) from Phytophthora cinnamomi–infected lupin seedlings were collected by headspace solid-phase microextraction (HS-SPME). The sampling was done 28 to 44, 52 to 68, and 76 to 92 h after inoculation (HAI). The HS-SPME samples were analyzed by gas chromatography-flame ionization detector (GC-FID) to assess the differences in volatile compounds between the P. cinnamomi–infected lupin seedlings and the control. Three specific peaks were identified after 52 to 68 h with the infected lupin seedlings, at which time there were no visible aboveground symptoms of infection. Subsequently, the VOCs of five different substrates (V8A, PDA, lupin seedlings, soil, and soil + lupin seedlings) infected with P. cinnamomi and the corresponding controls were analyzed by gas chromatography-mass spectrometry (GC/MS). A total of 87 VOCs were identified. Of these, the five most abundant that were unique to all five inoculated substrates included: 4-ethyl-2-methoxyphenol, 4-ethylphenol, butyrolactone, phenylethyl alcohol, and 3-hydroxy-2-butanone. Therefore, these metabolites can be used as markers for the identification of P. cinnamomi in different growing environments. Some VOCs were specific to a particular substrate; for example, 2,4,6-rrimethyl-heptanes, dl-6-methyl-5-hepten-2-ol, dimethyl trisulfide, 6,10-dimethyl- 5,9-undecadien-2-ol, and 2-methoxy-4-vinylphenol were specific to P. cinnamomi + V8A; heptanes and 5-methyl-3-heptaneone were specific to P. cinnamomi + PDA; 3-methyl-1-butanol, ethyl acetate, 2-methyl-propanoic acid, ethyl ester, and ethyl ester 2-methyl-butanoic acid were specific to P. cinnamomi–inoculated lupin seedlings; and benzyl alcohol and 4-ethyl-1, 2-dimethoxybenzene were only detected in the headspace of inoculated soil + lupin seedlings. Results from this investigation have multiple impacts as the volatile organic profiles produced by the pathogen can be utilized as an early warning system to detect the pathogen from contaminated field soil samples. Data from this investigation have also illuminated potential metabolic pathways utilized by the oomycete during infection which may serve as potential targets for the development of specific control strategies.
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Meyer, Elisabeth M., Thomas G. Ranney, Thomas A. Eaker, and Kelly Ivors. "Differential Resistance of Gordonieae Trees to Phytophthora cinnamomi." HortScience 44, no. 5 (August 2009): 1484–86. http://dx.doi.org/10.21273/hortsci.44.5.1484.
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Trees in the Theaceae tribe Gordonieae are valuable nursery crops, but some of these taxa are known to be highly susceptible to root rot caused by Phytophthora cinnamomi Rands. The objective of this study was to evaluate a collection of Gordonieae taxa for resistance to this pathogen. These taxa included Franklinia alatamaha Bart. Ex Marshall, Gordonia lasianthus (L.) Ellis, Schima wallichii Choisy, S. khasiana Dyer, ×Schimlinia floribunda Ranney & Fantz, and ×Gordlinia grandiflora Ranney & Fantz. Abies fraseri (Pursh) Poir. was also included in the study as a positive control. Container-grown trees were inoculated with three isolates of P. cinnamomi and symptoms were rated over an 84-day period during the summer of 2008. Disease symptom ratings from 1 (healthy) to 4 (dead) were collected twice weekly and area under the disease progress curve (AUDPC) values were calculated. None of the S. khasiana or S. wallichii exhibited any root rot symptoms or mortality, whereas the remaining species showed symptoms of infection at varying levels over time. Symptoms in F. alatamaha and A. fraseri were apparent before other taxa, and mortality for both species reached 100% by the end of the experiment. Comparison of AUDPC values indicated that F. alatamaha was the most susceptible followed by A. fraseri. There was no significant difference in AUDPC among the more resistant taxa, including G. lasianthus, both Schima species, and the intergeneric hybrids. Values for AUDPC in the hybrid taxa were similar to their more resistant parental genus, indicating that resistance to P. cinnamomi is a partially dominant trait in these plants. These results further suggest the potential to breed improved hybrids of Gordonieae trees with substantial resistance to P. cinnamomi.
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Rodríguez-Romero, Manuela, Belén Godoy-Cancho, Isabel M. Calha, José António Passarinho, and Ana Cristina Moreira. "Allelopathic Effects of Three Herb Species on Phytophthora cinnamomi, a Pathogen Causing Severe Oak Decline in Mediterranean Wood Pastures." Forests 12, no. 3 (March 2, 2021): 285. http://dx.doi.org/10.3390/f12030285.
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The ability of three herbaceous plants (Diplotaxis tenuifolia (L.) DC., Eruca vesicaria L. and Raphanus raphanistrum L.) from Iberian wood pastures to reduce Phytophthora cinnamomi Rands pathogen populations through allelopathic relationships is studied. The inhibitory capacity of their aqueous root extracts (AREs) on mycelial growth and production of P. cinnamomi reproductive structures is analysed in vitro. In addition, Quercus seedlings were grown in infested by P. cinnamomi-soils and with the presence or absence of allelopathic and susceptible herb species to the pathogen to assess the defensive chemical response of Quercus seedlings through their leaf phenolic compounds. Results show a strong inhibitory capacity of AREs on P. cinnamomi activity in vitro and a protective effect of these herb species on Quercus plants against P. cinnamomi in vivo. D. tenuifolia would be especially suited for biological control in the pathogen suppression.
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Li, Mingzhu, Qian Guo, Mengyi Liang, Qing Zhao, Tao Lin, Han Gao, Ayaka Hieno, et al. "Population Dynamics, Effective Soil Factors, and LAMP Detection Systems for Phytophthora Species Associated with Kiwifruit Diseases in China." Plant Disease 106, no. 3 (March 1, 2022): 846–53. http://dx.doi.org/10.1094/pdis-04-21-0852-re.
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China has the largest area of kiwifruit production in the world. Pathogens associated with root diseases of kiwi trees have not been investigated extensively. In this research, three Phytophthora species, Phytophthora cactorum, Phytophthora cinnamomi, and Phytophthora lateralis, which are pathogenic to kiwi trees in the main planting areas of China, were studied. The population densities of these species in 128 soil samples from 32 kiwi orchards in 2017 and 2018 were measured using multiplex real-time quantitative PCR based on the ras-related protein gene Ypt1. P. cactorum was the most widely distributed of the three species in orchards of the Zhouzhi and Meixian prefectures. We used redundancy analysis to examine soil factors in the kiwi orchards to understand their effects on the population densities of the Phytophthora species. The redundancy analysis indicated that soil temperature and pH were significantly correlated with the abundance of P. cactorum and P. cinnamomi. In addition, two loop-mediated isothermal amplification detection systems for P. cactorum were developed based on the tigA gene. The color-change detection system proved to be accurate, sensitive, and faster than quantitative PCR. The results of this study, along with the loop-mediated isothermal amplification detection systems, will be of great use in the control of Phytophthora diseases for the production of kiwifruits in China.
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Cahill, David M., James E. Rookes, Barbara A. Wilson, Lesley Gibson, and Keith L. McDougall. "Phytophthora cinnamomi and Australia's biodiversity: impacts, predictions and progress towards control." Australian Journal of Botany 56, no. 4 (2008): 279. http://dx.doi.org/10.1071/bt07159.
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Phytophthora cinnamomi continues to cause devastating disease in Australian native vegetation and consequently the disease is listed by the Federal Government as a process that is threatening Australia’s biodiversity. Although several advances have been made in our understanding of how this soil-borne pathogen interacts with plants and of how we may tackle it in natural systems, our ability to control the disease is limited. The pathogen occurs widely across Australia but the severity of its impact is most evident within ecological communities of the south-west and south-east of the country. A regional impact summary for all states and territories shows the pathogen to be the cause of serious disease in numerous species, a significant number of which are rare and threatened. Many genera of endemic taxa have a high proportion of susceptible species including the iconic genera Banksia, Epacris and Xanthorrhoea. Long-term studies in Victoria have shown limited but probably unsustainable recovery of susceptible vegetation, given current management practices. Management of the disease in conservation reserves is reliant on hygiene, the use of chemicals and restriction of access, and has had only limited effectiveness and not provided complete control. The deleterious impacts of the disease on faunal habitat are reasonably well documented and demonstrate loss of individual animal species and changes in population structure and species abundance. Few plant species are known to be resistant to P. cinnamomi; however, investigations over several years have discovered the mechanisms by which some plants are able to survive infection, including the activation of defence-related genes and signalling pathways, the reinforcement of cell walls and accumulation of toxic metabolites. Manipulation of resistance and resistance-related mechanisms may provide avenues for protection against disease in otherwise susceptible species. Despite the advances made in Phytophthora research in Australia during the past 40 years, there is still much to be done to give land managers the resources to combat this disease. Recent State and Federal initiatives offer the prospect of a growing and broader awareness of the disease and its associated impacts. However, awareness must be translated into action as time is running out for the large number of susceptible, and potentially susceptible, species within vulnerable Australian ecological communities.
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Jung, T., and G. Dobler. "First Report of Littleleaf Disease Caused by Phytophthora cinnamomi on Pinus occidentalis in the Dominican Republic." Plant Disease 86, no. 11 (November 2002): 1275. http://dx.doi.org/10.1094/pdis.2002.86.11.1275c.
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Pinus occidentalis Sw. is an endemic species of the Caribbean island of Hispaniola (Dominican Republic and Haiti). It shows an extreme ecological plasticity and grows on a wide range of soil types from 0 to 3,175 m in elevation with annual mean temperatures ranging from 6 to 25°C and annual precipitation of 800 to 2,300 mm. P. occidentalis is a major component of forests above 800 m in elevation and forms pure climax forests above 2,000 m (4). For more than 10 years, stands of P. occidentalis in the Sierra (Cordillera Central) growing on a wide range of site conditions have suffered from a serious widespread disease. Symptoms include yellowing and dwarfing of needles, a progressive defoliation and dieback of the crown, and finally, death of weakened trees often caused by attacks by secondary bark beetles. Mature stands are mainly affected, but the disease is also present in plantations and natural regeneration that is older than 10 years. Disease spread is rapid, and occurs mainly along roads and from diseased trees downslope following the path of water runoff. Initially, Leptographium serpens was isolated from necrotic roots and was thought to be the causal agent (1). However, the symptoms of the disease more closely resemble those of littleleaf disease of P. echinata and P. taeda in the southeastern United States, which is caused by the aggressive fine-root pathogen Phytophthora cinnamomi Rands (3). Moreover, spread and dynamics of the disease are similar to the diebacks of Chamaecyparis lawsoniana in Oregon and Eucalyptus spp. in western Australia, which are caused by the introduced soilborne pathogens Phytophthora lateralis and Phytophthora cinnamomi, respectively. Soil samples containing the rhizosphere and fine roots of diseased P. occidentalis trees were collected in February 2002 at five sites near Celestina and Los Montones (Dominican Republic) and transported to the Bavarian State Institute of Forestry. The pathogen was baited from the soil by floating 3- to 7-dayold leaves of Quercus robur seedlings over flooded soil and placing the leaves on selective PARPNH agar (2). Phytophthora cinnamomi was isolated from the soil of all five sites. Crossing with A1 and A2 tester strains of Phytophthora cinnamomi confirmed that all isolates belong to the A2 mating type. In cross sections of necrotic fine roots, characteristic structures of Phytophthora cinnamomi such as nonseptate hyphae and chlamydospores could be observed. Our results indicate that the disease of P. occidentalis is caused by the introduced pathogen Phytophthora cinnamomi. Because of the ecological and economical importance of P. occidentalis, the disease poses a major threat to forestry in the Dominican Republic. Future research should include the mapping of the disease, pathogenicity tests on P. occidentalis and alternative pine species, in particular P. caribaea, screening for resistance in the field, and testing of systemic fungicides such as potassium phosphonate, which is known to be effective against Phytophthora cinnamomi. References: (1) G. Dobler. Manejo y Tablas de Rendimiento de Pinus occidentalis. Plan Sierra, San José de las Matas, Dominican Republic, 1999. (2) T. Jung et al. Plant Pathol. 49:706, 2000. (3) S. W. Oak and F. H. Tainter. How to identify and control littleleaf disease. Protection Rep. R8-PR12, USDA Forest Service Southern Region, Atlanta, Georgia, 1988. (4) L. Sprich. Allg. Forst. Jagdztg. 168:67, 1997.
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Irwin, JAG, DM Cahill, and A. Drenth. "Phytophthora in Australia." Australian Journal of Agricultural Research 46, no. 7 (1995): 1311. http://dx.doi.org/10.1071/ar9951311.
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Phytophthora spp. are one of Australia's most serious plant pathogens, causing well in excess of $200 million in lost production annually across all of our plant-based industries. Of the more than 50 species of Phytophthora recorded worldwide, over 20 are present in Australia. All species, along with their hosts, distribution and current control measures have been tabulated. Use of molecular markers to analyse population genetic structure has shown that most of these pathogens have been introduced from overseas, and become widely distributed in Australia within relatively short periods of time. The review highlights the general biology of Phytophthora spp. and their impact on agricultural production in Australia, with particular emphasis on the genetics of host/pathogen interactions, population genetic structure and reproduction of Phytophthora populations in Australia. The review highlights the role molecular technologies may play in developing an understanding of host-pathogen recognition and pathogenesis in Phytophthora. Three case histories, involving P. sojae, P. medicaginis and P. cinnamomi, have been developed to provide insights into current levels of understanding, and to identify gaps in our knowledge. Current control measures are summarized and possible new avenues of control discussed.
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Ownley, B. H., and D. M. Benson. "Evaluation of Penicillium janthinellum as a Biological Control of Phytophthora Root Rot of Azalea." Journal of the American Society for Horticultural Science 117, no. 3 (May 1992): 407–10. http://dx.doi.org/10.21273/jashs.117.3.407.
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Wheat bran inoculum of Penicillium janthinellum (Biourge) [1% w/w added to pine bark (PB) container medium] suppressed “`root rot of azalea (Rhododendron obtusum Planch.) caused by Phytophthora cinnamomi Rands in greenhouse experiments. Shoot fresh weight was increased by 31% to 91% and mortality reduced by 30% to 50% for azaleas planted in natural (nonsterile) PB amended with P. janthinellum compared with the infested control. The population densities of P. janthinellum exceeded 105 to 106 cfu/g dry PB within 7 days and remained stable over time. Penicillium janthinellum, a natural colonizer of PB container media, shows potential as a biological control of phytophthora root rot of azalea.
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Shearer, B. L., C. E. Crane, S. Barrett, and A. Cochrane. "Phytophthora cinnamomi invasion, a major threatening process to conservation of flora diversity in the South-west Botanical Province of Western Australia." Australian Journal of Botany 55, no. 3 (2007): 225. http://dx.doi.org/10.1071/bt06019.
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The invasive soilborne plant pathogen Phytophthora cinnamomi Rands is a major threatening process in the South-west Botanical Province of Western Australia, an internationally recognised biodiversity hotspot. Comparatively recent introduction of P. cinnamomi into native plant communities of the South-west Botanical Province of Western Australia since the early 1900s has caused great irreversible damage and altered successional change to a wide range of unique, diverse and mainly susceptible plant communities. The cost of P. cinnamomi infestation to community values is illustrated by examination of direct (mortality curves, changes in vegetation cover) and indirect impacts on biodiversity and ecosystem dynamics, the proportion of Threatened Ecological Communities infested, Declared Rare Flora either directly or indirectly threatened by infestation and estimates of the proportion of the native flora of the South-west Botanical Province susceptible to the pathogen. While direct impacts of P. cinnamomi have been poorly documented in the South-west Botanical Province, even less attention has been given to indirect impact where destruction of the habitat by the pathogen affects taxa not directly affected by infection. Current poor understanding and quantification of indirect impacts of P. cinnamomi through habitat destruction results in an underestimation of the true impact of the pathogen on the flora of the South-west Botanical Province. Considerable variation of susceptibility to P. cinnamomi among and within families of threatened flora and responses of taxa within the genus Lambertia show how classification within family and genus are poor predictors of species susceptibility. Within apparently susceptible plant species, individuals are resistant to P. cinnamomi infection. Intra-specific variation in susceptibility can be utilised in the long-term management of threatened flora populations and needs to be a high research priority. Current control strategies for conservation of flora threatened by P. cinnamomi integrate hygiene and ex situ conservation with disease control using fungicide. Application of the fungicide phosphite has proven effective in slowing progress of P. cinnamomi in infested, threatened communities. However, variation in plant species responses to phosphite application is a major factor influencing effective control of P. cinnamomi in native communities. A greater understanding of the mechanisms of action of phosphite in plant species showing different responses to the fungicide may provide options for prescription modification to increase phosphite effectiveness in a range of plant species. The range of responses to P. cinnamomi infection and phosphite application described for Lambertia taxa suggests that the genus would make an ideal model system to elucidate the mechanisms of resistance to P. cinnamomi and the effectiveness of phosphite against the pathogen.
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Shearer, BL, and M. Dillon. "Impact and Disease Centre Characteristics of Phytophthora cinnamomi Infestations of Banksia Woodlands on the Swan Coastal Plain, Western Australia." Australian Journal of Botany 44, no. 1 (1996): 79. http://dx.doi.org/10.1071/bt9960079.
Full textAbstract:
Phytophthora cinnamomi Rands was isolated from either dead plants or soil at 46 disease centres in Banksia woodland at national parks and reserves on the Swan Coastal Plain. Phytophthora cryptogea Pethybridge & Lafferty was also isolated from roots of dead Acacia pulchella R.Br. in one disease centre infected with P. cinnamomi. Dead plants were infected with Armillaria luteobubalina Watling & Kile in four disease centres on the Spearwood Dune System, and these centres were excluded from further analysis. Phytophthora cinnamomi diseased areas ranged from 0.01 to 30 ha in size (mean 1.6 ± s.e. 0.7 ha). The total area infested for the 46 disease centres was 71.5 ha. Impact of P. cinnamomi was high in 17% of disease centres and low in 11% of disease centres. Age of plant death was a mixture of old and recent in 85% of disease centres. Mainly old deaths occurred in only 4% of disease centres. The proportion of species dying in infested areas varied between 10-64% (mean 28 ± s.e. 2%) and was positively correlated with impact type. It was found that infestation decreased species number; on average, there were seven fewer species in infested compared to non-infested areas. Four plant species associated with moist sandy sites tended to occur more frequently in centres of high impact than by chance alone. Occurrence of P. cinnamomi was related to soil association with soils of 60% of the disease centres belonging to the Bassendean or Southern River associations of the Bassendean Dune System. Sixteen percent of disease centres occurred in the Cannington, Guildford and Serpentine River associations of the Pinjarra Plain. No disease centres of P. cinnamomi were found on soils of the Speanvood and Quindalup Dune Systems. A water table was found within 3 m of the soil surface in 48% of the centres. Disturbance was associated with all disease centres. Firebreaks were associated with 72% of disease centres. Banksia woodland remnants on the Bassendean Dune System and the Pinjarra Plain are highly vulnerable to infection by P. cinnamomi and their conservation requires control of existing infestatinns and protection from introduction af the pathogen.
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Parke, Jennifer L., Brian J. Knaus, Valerie J. Fieland, Carrie Lewis, and Niklaus J. Grünwald. "Phytophthora Community Structure Analyses in Oregon Nurseries Inform Systems Approaches to Disease Management." Phytopathology® 104, no. 10 (October 2014): 1052–62. http://dx.doi.org/10.1094/phyto-01-14-0014-r.
Full textAbstract:
Nursery plants are important vectors for plant pathogens. Understanding what pathogens occur in nurseries in different production stages can be useful to the development of integrated systems approaches. Four horticultural nurseries in Oregon were sampled every 2 months for 4 years to determine the identity and community structure of Phytophthora spp. associated with different sources and stages in the nursery production cycle. Plants, potting media, used containers, water, greenhouse soil, and container yard substrates were systematically sampled from propagation to the field. From 674 Phytophthora isolates recovered, 28 different species or taxa were identified. The most commonly isolated species from plants were Phytophthora plurivora (33%), P. cinnamomi (26%), P. syringae (19%), and P. citrophthora (11%). From soil and gravel substrates, P. plurivora accounted for 25% of the isolates, with P. taxon Pgchlamydo, P. cryptogea, and P. cinnamomi accounting for 18, 17, and 15%, respectively. Five species (P. plurivora, P. syringae, P. taxon Pgchlamydo, P. gonapodyides, and P. cryptogea) were found in all nurseries. The greatest diversity of taxa occurred in irrigation water reservoirs (20 taxa), with the majority of isolates belonging to internal transcribed spacer clade 6, typically including aquatic opportunists. Nurseries differed in composition of Phytophthora communities across years, seasons, and source within the nursery. These findings suggest likely contamination hazards and target critical control points for management of Phytophthora disease using a systems approach.
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Downer, Jim, Ben Faber, and John Menge. "Factors Affecting Root Rot Control in Mulched Avocado Orchards." HortTechnology 12, no. 4 (January 2002): 601–5. http://dx.doi.org/10.21273/horttech.12.4.601.
Full textAbstract:
Mulches can exert positive (disease controlling) or negative (disease enhancing) potential when applied to young avocado (Persea americana) trees. Regulation of root disease in avocado is a complicated process that is affected by host resistance, inoculum density, temperature, soil salinity and soil water potential. There are short-term immediate effects from mulching and subtle long-term effects that regulate disease caused by the root rot pathogen Phytophthora cinnamomi. Short-term effects include increased soil moisture and soil temperature moderation. Long-term effects include increases of: soil mineral nutrients, soil aggregation and drainage; microbial activity; and cellulase enzyme activities. Biological control of Phytophthora in mulched soil is partially regulated by cellulase enzyme activities. This soil enzyme concept of biological control is discussed in regard to the classical Ashburner method of biological control.
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Benson, D. M., J. R. Sidebottom, and J. Moody. "Control of Phytophthora Root Rot in Field Plantings of Fraser Fir with Fosetyl-Al and Mefenoxam." Plant Health Progress 7, no. 1 (January 2006): 25. http://dx.doi.org/10.1094/php-2006-0331-01-rs.
Full textAbstract:
Fungicides were evaluated for control of Phytophthora root rot for five growing seasons in two field plantings of Fraser fir (Abies fraseri) affected by Phytophthora cinnamomi in western North Carolina. At the first site, which had a fairly well-drained soil, treatment programs with Aliette (5 lb/100 gal, three applications per year), Subdue Maxx (3.7 fl oz/1.15 gal/1000 ft2, two applications per year), and Subdue GR (5.75 lb/1000 ft2, two applications per year) maintained low rates of mortality (< 10%) for three growing seasons, whereas tree mortality in the untreated plots reached 13 and 37% by the second and third growing seasons, respectively. At the second site, which was in a flood plain, disease did not develop during the first 2.5 years, even in untreated control plots. However, mortality increased rapidly following several high-rainfall events, but none of the fungicides had any effect on disease development. Apparently, at least under conditions not overly conducive to the disease, the fungicide treatment programs can delay the onset of high mortality rates caused by P. cinnamomi in Fraser fir for up to three growing seasons. Accepted for publication 23 February 2006. Published 31 March 2006.
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Weiland, Jerry E., Carolyn F. Scagel, Niklaus J. Grünwald, E. Anne Davis, Bryan R. Beck, and Jesse N. Mitchell. "Irrigation Frequency and Volume has Little Influence on Phytophthora Root Rot in Container-grown Rhododendron." Journal of Environmental Horticulture 40, no. 2 (June 1, 2022): 67–78. http://dx.doi.org/10.24266/2573-5586-40.2.67.
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Abstract We evaluated whether reducing irrigation frequency and volume alters the ability of Phytophthora plurivora and P. cinnamomi to cause root rot on rhododendron grown in a noninfested potting medium or media infested with 1 or 100 propagules per gram (ppg) of pathogen. Plants were irrigated to maintain a substrate moisture of >70% container capacity (1.0X), one-half volume of 1.0X (0.5X), or two times the volume of 1.0X at each irrigation event for one week, followed by no irrigation, until soil moisture reached <50% container capacity. Aboveground disease symptoms (chlorosis, stomatal conductance, wilting, and plant death) were evaluated weekly and root rot, pathogen presence, plant biomass, and nutrient uptake were measured at the end of each trial. Both pathogens generally caused mild disease at 1 ppg and severe disease at 100 ppg. Reducing irrigation did little to lessen disease caused by either pathogen once infection had occurred. Instead, severe root infection often led to increased soil moisture and root rot across all irrigation treatments as roots became progressively compromised in their ability to take up water. Results show that reducing irrigation after infection has occurred is unlikely to effectively control root rot. Species used in this study: Phytophthora species (Phytophthora cinnamomi Rands; Phytophthora plurivora T. Jung and T.I. Burgess); rhododendron, Rhododendron catawbiense Michx. ‘Album', ‘Roseum Elegans', and ‘Roseum Pink'.
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Arroyo Cordero, Francisco Teodoro, Rocío Rodríguez-Arcos, Ana Jiménez-Araujo, Rafael Guillén-Bejarano, María José Basallote, and Carmen Barrau. "Inhibitory effect of the glucosinolate–myrosinase system on Phytophthora cinnamomi and Pythium spiculum." Plant Protection Science 55, No. 2 (February 17, 2019): 93–101. http://dx.doi.org/10.17221/98/2018-pps.
Full textAbstract:
Glucosinolate extracts from sprouts of common Brassica nigra, B. juncea cv. Scala, B. carinata cv. Eleven, and Sinapis alba cv. Ludique were analysed by reversed phase high-performance liquid chromatography-diode array detection-mass spectrometry. The effect of the glucosinolate–myrosinase system on in vitro mycelial growth of Phytophthora cinnamomi Rands and Pythium spiculum B. Paul was assessed. Likewise, sinigrin and sinalbin monohydrate commercial standards were also tested. The extracts from B. carinata, which contained 159 mmol/g plant DW equivalent (85% sinigrin, 5% gluconapin, and 3% glucotropaeolin), were the most effective against Phytophthora and Pythium isolates used in this study. However, the extract from S. alba, which contained 1 180 mmol/g (100% sinalbin), did not inhibit the mycelial growth of the isolates tested. The use of the glucosinolate-myrosinase system provides important additional information to advance in the implementation of field application of brassicaceous amendments for the control of soil-borne pathogens.
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Marks, GC, and IW Smith. "Metalaxyl and phosphonate as prophylactic and curative agents against stem infection of Leucadendron caused by Phytophthora cinnamomi." Australian Journal of Experimental Agriculture 32, no. 2 (1992): 255. http://dx.doi.org/10.1071/ea9920255.
Full textAbstract:
Neither metalaxyl (100 mL of a solution of 2.0 g a.i./L, applied as a root drench to 10-L pots) nor phosphonate (foliar spray at 1.0 g a.i./L, applied to runoff) controlled Phytophthora cinnamomi stem infection of Leucadendron laureolum x L. salignum hybrid when applied 10 days after inoculation. Both fungicides were most effective when applied prior to inoculation. Neither fungicide was able to kill P. cinnamomi within established infections. The fungus survived within the vascular tissues of treated plants. Infection was confined to cortical tissue by wound periderm when the rate of tissue invasion by P. cinnamomi was slowed by the fungicides. The results confirm observations made in protea growers' fields that with highly susceptible species, systemic fungicides can have poor curative properties and should be used as a prophylactic, in conjunction with other disease control methods.
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Weiland, Jerry E., Carolyn F. Scagel, Niklaus J. Grünwald, E. Anne Davis, Bryan R. Beck, Zachary S. L. Foster, and Valerie J. Fieland. "Soilborne Phytophthora and Pythium Diversity From Rhododendron in Propagation, Container, and Field Production Systems of the Pacific Northwest." Plant Disease 104, no. 6 (June 2020): 1841–50. http://dx.doi.org/10.1094/pdis-08-19-1672-re.
Full textAbstract:
Rhododendron root rot is a severe disease that causes significant mortality in rhododendrons. Information is needed about the incidence and identity of soilborne Phytophthora and Pythium species causing root rot in Pacific Northwest nurseries in order to better understand the disease etiology and to optimize disease control strategies. The last survey focusing solely on soilborne oomycete pathogens in rhododendron production was conducted in 1974. Since then, advances in pathogen identification have occurred, new species may have been introduced, pathogen communities may have shifted, and little is known about Pythium species affecting this crop. Therefore, a survey of root-infecting Phytophthora and Pythium species was conducted at seven nurseries from 2013 to 2017 to (i) document the incidence of root rot damage at each nursery and stage of production, (ii) identify soilborne oomycetes infecting rhododendron, and (iii) determine whether there are differences in pathogen diversity among nurseries and production systems. Rhododendrons from propagation, container, and field systems were sampled and Phytophthora and Pythium species were isolated from the roots and collar region. Root rot was rarely evident in propagation systems, which were dominated by Pythium species. However, severe root rot was much more common in container and field systems where the genus Phytophthora was also more prevalent, suggesting that Phytophthora species are the primary cause of severe root rot and that most contamination by these pathogens comes in after the propagation stage. In total, 20 Pythium species and 11 Phytophthora species were identified. Pythium cryptoirregulare, Pythium aff. macrosporum, Phytophthora plurivora, and Phytophthora cinnamomi were the most frequently isolated species and the results showed that Phytophthora plurivora has become much more common than in the past. Phytophthora diversity was also greater in field systems than in propagation or container systems. Risks for Phytophthora contamination were commonly observed during the survey and included placement of potting media in direct contact with field soil, the presence of dead plants that could serve as continuous sources of inoculum, and the presence of excess water as a result of poor drainage, overirrigation, or malfunctioning irrigation equipment. In the past, research on disease development and root rot disease control in rhododendron focused almost exclusively on Phytophthora cinnamomi. More research is needed on both of these topics for the other root-infecting species identified in this survey.
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Matei, Petruta, Jesús Martín-Gil, Beatrice Michaela Iacomi, Eduardo Pérez-Lebeña, María Barrio-Arredondo, and Pablo Martín-Ramos. "Silver Nanoparticles and Polyphenol Inclusion Compounds Composites for Phytophthora cinnamomi Mycelial Growth Inhibition." Antibiotics 7, no. 3 (August 16, 2018): 76. http://dx.doi.org/10.3390/antibiotics7030076.
Full textAbstract:
Phytophthora cinnamomi, responsible for “root rot” or “dieback” plant disease, causes a significant amount of economic and environmental impact. In this work, the fungicide action of nanocomposites based on silver nanoparticles and polyphenol inclusion compounds, which feature enhanced bioavailability and water solubility, was assayed for the control of this soil-borne water mold. Inclusion compounds were prepared by an aqueous two-phase system separation method through extraction, either in an hydroalcoholic solution with chitosan oligomers (COS) or in a choline chloride:urea:glycerol deep eutectic solvent (DES). The new inclusion compounds were synthesized from stevioside and various polyphenols (gallic acid, silymarin, ferulic acid and curcumin), in a [6:1] ratio in the COS medium and in a [3:1] ratio in the DES medium, respectively. Their in vitro response against Phytophthora cinnamomi isolate MYC43 (at concentrations of 125, 250 and 500 µg·mL−1) was tested, which found a significant mycelial growth inhibition, particularly high for the composites prepared using DES. Therefore, these nanocomposites hold promise as an alternative to fosetyl-Al and metalaxyl conventional systemic fungicides.
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Brown, Matthew S., Fulya Baysal-Gurel, Jason B. Oliver, and Karla M. Addesso. "Comparative Performance of Fungicides, Biofungicides, and Host Plant Defense Inducers in Suppression of Phytophthora Root Rot in Flowering Dogwood During Simulated Root Flooding Events." Plant Disease 103, no. 7 (July 2019): 1703–11. http://dx.doi.org/10.1094/pdis-09-18-1597-re.
Full textAbstract:
During flooding events in nurseries, Phytophthora root rot caused by Phytophthora cinnamomi Rands often causes damage that leads to complete crop loss. In this study, we evaluated the efficacy of fungicides, biofungicides, and host plant defense inducers for preventive and curative control of Phytophthora root rot on flowering dogwood (Cornus florida L.) seedlings exposed to a simulated flood event of 1, 3, or 7 days. In two greenhouse trials, preventive (7 days before flooding) or curative (1 day after flooding) drench treatments were applied to dogwood seedlings artificially inoculated with P. cinnamomi. The plants were flooded by maintaining standing water for 1, 3, or 7 days. After the trials, plant growth data (total plant weight, root weight, plant height, and plant width) were recorded, and root systems were assessed for disease severity using a scale of 0 to 100% of roots affected, and subsamples were plated on PARPH-V8 medium to determine the percent recovery of the Phytophthora pathogen. Plants preventively treated with Subdue MAXX had reduced disease severity relative to the nontreated, inoculated plants (positive control) flooded 1, 3, or 7 days in both trials. Pageant Intrinsic and Segovis treatments also had lower disease severity than the positive control at all flooding durations in trial two, but not trial one. In trial one, preventive and curative treatments of Orkestra Intrinsic had reduced disease severity compared with the positive control at 1 and 3 days of flooding, whereas curative treatments of Empress Intrinsic and Tartan Stressgard also were effective at 1 and 3 days of flooding in trial one. The host plant defense inducers (Aliette 80 WDG, Signature Xtra, and Actigard) were inconsistent and ineffective at reducing disease severity when applied as preventive or curative treatments. Preventive treatments of the biofungicides RootShield Plus+and MBI-110 had consistently lower disease severity than the positive control at 1 day of flooding but not 3 or 7 days of flooding. Potentially, growers can use information from this study to manage Phytophthora root rot during flooding or in areas of the nursery that often experience high soil moisture levels.
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Crane, C. E., and B. L. Shearer. "Comparison of phosphite application methods for control of Phytophthora cinnamomi in threatened communities." Australasian Plant Pathology 43, no. 2 (November 20, 2013): 143–49. http://dx.doi.org/10.1007/s13313-013-0260-9.
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Thinggaard, K., and B. Toppe. "First Report of Phytophthora cinnamomi Root Rot, Stem, and Leaf Blight on Ivy." Plant Disease 81, no. 8 (August 1997): 960. http://dx.doi.org/10.1094/pdis.1997.81.8.960c.
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Phytophthora cinnamomi was isolated from varieties of Hedera helix pot plants in 1989 in two Danish greenhouse nurseries. The symptoms were brown, rotten roots and stems, and brown areas developing from the base of the leaves. The fungus was isolated directly from roots, stems, leaves, and soil, and by baiting the nutrient solutions of the watering systems with needles of Cedrus deodara. The fungus was isolated on Phytophthora selective agar medium containing hymexazol and identified with the keys of Kröber (1) and Stamps et al. (2). The fungus was characterized by coralloid hyphal swellings, chlamydospores, lack of oogonia in single culture, and production of numerous, ovoid sporangia with a nonpapillate, wide pore. The sporangia produced many zoospores after 2 days flooding with autoclaved pond water on V8 juice agar, followed by internal proliferation. The fungus was also isolated in Norway in 1993 from ivy pot plants. The fungus was widespread in Danish and Norwegian pot plant nurseries in 1997 and caused losses in most varieties, especially at temperatures above 23°C. Effective fungicides are not available for use in Denmark and the disease is easily spread with cuttings, and through the watering system with recirculation of the nutrient solution. A Danish isolate of P. cinnamomi originating from roots of H. helix was used in a pathogenicity test. Five-week-old cuttings were inoculated by adding zoospores (5 per ml) to the recirculating nutrient solution. Control plants were on a separate bench with nutrient solution without the fungus. After 1 week, symptoms of root rot were observed, and 2 weeks after inoculation, 75% of plants expressed severe symptoms on roots, stems, and leaves. P. cinnamomi was reisolated from roots, stems, and leaves of diseased plants, but was not isolated from the control plants. The reisolate was morphologically identical to the original isolate. This is the first report of P. cinnamomi from ivy in Europe. References: (1) H. Kröber. Mitt. Biol. Bundesanst. Land Forstwirtsch. Berlin-Dahlem 225:73, 1985. (2) D. J. Stamps et al. 1990. Mycol. Pap. No. 162. CAB Int. Mycol. Inst., Kew, England.
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Schwingle, B. W., J. Juzwik, J. Eggers, and B. Moltzan. "Phytophthora Species in Soils Associated with Declining and Nondeclining Oaks in Missouri Forests." Plant Disease 91, no. 5 (May 2007): 633. http://dx.doi.org/10.1094/pdis-91-5-0633a.
Full textAbstract:
Periodic episodes of oak decline have occurred in the Missouri Ozark forests since the early 1900s and the disease is currently severe (2). Several Phytophthora spp. contribute to oak decline in Europe (1), but the role of Phytophthora spp. in oak decline in the eastern United States is not known. Mineral soils collected around the bases of declining and nondeclining oaks in paired sites in central Missouri forests were assayed for the presence of these taxa by baiting flooded soil with Quercus robur leaves. Q. rubra and Q. velutina were the oak species on three sites and Q. alba was on the fourth. Isolates from symptomatic baits plated on PARPNH selective medium were identified tentatively on classical taxonomic characteristics. Five isolates of P. cambivora, two of P. quercina, and eight of P. cinnamomi were obtained from soils around one, one, and three trees, respectively, on decline sites. The internal transcribed spacer sequences for each isolate were compared to those in GenBank; BLAST searches for all isolates had nucleotide identities of 99% and E values of 0, which confirmed the identifications. Greenhouse pot trials were conducted to assess pathogenicity of isolates on stems of 2-year-old Q. alba and Q. rubra. A mycelial agar plug was inserted into a 1-cm long slit cut into the cambium 5 cm above the root collar and covered with sterile, moist cotton and wrapped with laboratory film. The treatments included two isolates of P. cambivora, one of P. quercina, three of P. cinnamomi, and a sterile agar plug. Each host × isolate combination was replicated four times, and the experiment was conducted twice in the greenhouse (natural lighting; temperature ≤32°C in summer and ≥7°C in winter). Stem lesions were produced commonly by P. cambivora (28 of 32 seedlings) and P. cinnamomi (46 of 48 seedlings) within 3 months; none was found on control seedlings or those inoculated with P. quercina. Mean lengths (cm) of lesions caused by P. cinnamomi were greater for Q. rubra (5.6) than for Q. alba (4.3) and lesion lengths for P. cambivora were greater for Q. alba (5.2) than for Q. rubra (4.4). Seven Q. alba seedlings inoculated with P. cambivora and one Q. alba inoculated with P. cinnamomi died before 3 months. All Phytophthora species were recovered from inoculated stems at 3 months except that P. quercina was not recovered in one trial. To our knowledge, this is the first report of Phytophthora species in soils of Missouri oak forests, of P. quercina in the United States, and of the ability of P. cambivora to cause stem lesions on Q. alba. P. cinnamomi and P. cambivora should be investigated in situ as possible contributing factors of oak decline in Missouri. References: (1) T. Jung et al. Plant Pathol. 49:706, 2000. (2) R. Lawrence et al. MO. Conserv. 63:11, 2002.
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Lawrence, Scott A., Hannah F. Robinson, Daniel P. Furkert, Margaret A. Brimble, and Monica L. Gerth. "Screening a Natural Product-Inspired Library for Anti-Phytophthora Activities." Molecules 26, no. 7 (March 24, 2021): 1819. http://dx.doi.org/10.3390/molecules26071819.
Full textAbstract:
Phytophthora is a genus of microorganisms that cause devastating dieback and root-rot diseases in thousands of plant hosts worldwide. The economic impact of Phytophthora diseases on crops and native ecosystems is estimated to be billions of dollars per annum. These invasive pathogens are extremely difficult to control using existing chemical means, and the effectiveness of the few treatments available is being jeopardized by increasing rates of resistance. There is an urgent need to identify new chemical treatments that are effective against Phytophthora diseases. Natural products have long been regarded as “Nature’s medicine chest”, providing invaluable leads for developing front-line drugs and agrochemical agents. Here, we have screened a natural product-inspired library of 328 chemicals against two key Phytophthora species: Phytophthora cinnamomi and Phytophthora agathidicida. The library was initially screened for inhibition of zoospore germination. From these screens, we identified twenty-one hits that inhibited germination of one or both species. These hits were further tested in mycelial growth inhibition studies to determine their half-maximal inhibitory concentrations (IC50s). Four compounds had IC50 values of approximately 10 µM or less, and our best hit had IC50s of approximately 3 µM against both Phytophthora species tested. Overall, these hits may serve as promising leads for the development of new anti-Phytophthora agrochemicals
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Yeo, John R., Jerry E. Weiland, Dan M. Sullivan, and David R. Bryla. "Nonchemical, Cultural Management Strategies to Suppress Phytophthora Root Rot in Northern Highbush Blueberry." HortScience 52, no. 5 (May 2017): 725–31. http://dx.doi.org/10.21273/hortsci11437-16.
Full textAbstract:
Phytophthora cinnamomi Rands causes root rot of northern highbush blueberry (Vaccinium corymbosum L.), which decreases plant growth, yield, and profitability for growers. Fungicides are available to suppress the disease, but are prone to development of resistance in target pathogens and cannot be used in certified organic production systems. Alternative, nonchemical, cultural management strategies were evaluated to reduce phytophthora root rot in a field infested with P. cinnamomi. The field was planted with ‘Draper’ blueberry, which is highly susceptible to the pathogen. The soil was either amended with gypsum or not before planting, and the plants were irrigated using narrow (adjacent to plant crown) or widely spaced (20 cm on either side of the plant crown) drip lines and mulched with douglas fir sawdust or black, woven geotextile fabric (weed mat). A fungicide control treatment was also included in the study and consisted of applying two conventional fungicides, mefenoxam and fosetyl-Al, to plants irrigated with narrow drip lines and mulched with sawdust. Initially, root infection by P. cinnamomi was lower with the combination of gypsum, wide drip lines, and sawdust mulch than with any other treatment, except the fungicide control. The soil under weed mat accumulated more heat units than under sawdust and resulted in faster hyphal growth by the pathogen. However, plant growth was similar in both mulch types. The effects of drip line placement and gypsum, on the other hand, were interactive, and plants grown with a combination of wide drip lines and gypsum produced the greatest amount of biomass among the cultural treatments. Narrow drip lines negated the disease-suppressive effects of gypsum by moving zoospore-inhibiting Ca2+ away from the plant root zone, and also resulted in wetter soil near the crown of the plants, which likely promoted zoospore discharge and root infection. However, wide drip lines resulted in N deficiency symptoms during the first year after planting and, therefore, resulted in less plant growth than the fungicide control. Thus, if N is managed properly, this study suggests that concerted use of gypsum and wide drip lines can help suppress phytophthora root rot in northern highbush blueberry and increase production in field soils where the pathogen is present.