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1
Ossowicki, Adam, Vittorio Tracanna, Marloes L. C. Petrus, Gilles van Wezel, Jos M. Raaijmakers, Marnix H. Medema, and Paolina Garbeva. "Microbial and volatile profiling of soils suppressive to Fusarium culmorum of wheat." Proceedings of the Royal Society B: Biological Sciences 287, no. 1921 (February 19, 2020): 20192527. http://dx.doi.org/10.1098/rspb.2019.2527.
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In disease-suppressive soils, microbiota protect plants from root infections. Bacterial members of this microbiota have been shown to produce specific molecules that mediate this phenotype. To date, however, studies have focused on individual suppressive soils and the degree of natural variability of soil suppressiveness remains unclear. Here, we screened a large collection of field soils for suppressiveness to Fusarium culmorum using wheat ( Triticum aestivum ) as a model host plant. A high variation of disease suppressiveness was observed, with 14% showing a clear suppressive phenotype. The microbiological basis of suppressiveness to F. culmorum was confirmed by gamma sterilization and soil transplantation. Amplicon sequencing revealed diverse bacterial taxonomic compositions and no specific taxa were found exclusively enriched in all suppressive soils. Nonetheless, co-occurrence network analysis revealed that two suppressive soils shared an overrepresented bacterial guild dominated by various Acidobacteria. In addition, our study revealed that volatile emission may contribute to suppression, but not for all suppressive soils. Our study raises new questions regarding the possible mechanistic variability of disease-suppressive phenotypes across physico-chemically different soils. Accordingly, we anticipate that larger-scale soil profiling, along with functional studies, will enable a deeper understanding of disease-suppressive microbiomes.
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Jauri, Patricia Vaz, Nora Altier, Carlos A. Pérez, and Linda Kinkel. "Cropping History Effects on Pathogen Suppressive and Signaling Dynamics in Streptomyces Communities." Phytobiomes Journal 2, no. 1 (January 2018): 14–23. http://dx.doi.org/10.1094/pbiomes-05-17-0024-r.
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Diseases remain a yield-limiting factor for crops despite the availability of control measures for many pathogens. Indigenous soil microorganisms can suppress some plant pathogens, yet there is little systematic information on the effects of cropping systems on disease-suppressive populations in soil. Streptomyces have been associated with suppression of plant diseases in several naturally occurring disease-suppressive soils. Pathogen-suppressive activity of Streptomyces communities is correlated with higher bacterial densities and with inhibitory phenotypes, driven by competition among indigenous soil bacteria. We sought to characterize relationships between cropping practices and pathogen suppression among soil Streptomyces. We evaluated bacterial and Streptomyces densities and inhibitory activities in soils from a long-term crop rotation experiment. Signaling interactions that altered inhibitory phenotypes among sympatric populations were also evaluated for a subset of samples. Soils from longer rotations, which had a higher number of plant species over time, had larger bacterial and Streptomyces densities, and more inhibitors than soils from shorter rotations. In addition, signaling occurred more frequently among isolates from higher-density communities. Our work shows that bacterial density, pathogen suppression and signaling are interrelated and are affected by crop rotation, suggesting the potential for management to optimize suppressive populations.
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Schlatter, Daniel, Linda Kinkel, Linda Thomashow, David Weller, and Timothy Paulitz. "Disease Suppressive Soils: New Insights from the Soil Microbiome." Phytopathology® 107, no. 11 (November 2017): 1284–97. http://dx.doi.org/10.1094/phyto-03-17-0111-rvw.
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Soils suppressive to soilborne pathogens have been identified worldwide for almost 60 years and attributed mainly to suppressive or antagonistic microorganisms. Rather than identifying, testing and applying potential biocontrol agents in an inundative fashion, research into suppressive soils has attempted to understand how indigenous microbiomes can reduce disease, even in the presence of the pathogen, susceptible host, and favorable environment. Recent advances in next-generation sequencing of microbiomes have provided new tools to reexamine and further characterize the nature of these soils. Two general types of suppression have been described: specific and general suppression, and theories have been developed around these two models. In this review, we will present three examples of currently-studied model systems with features representative of specific and general suppressiveness: suppression to take-all (Gaeumannomyces graminis var. tritici), Rhizoctonia bare patch of wheat (Rhizoctonia solani AG-8), and Streptomyces. To compare and contrast the two models of general versus specific suppression, we propose a number of hypotheses about the nature and ecology of microbial populations and communities of suppressive soils. We outline the potential and limitations of new molecular techniques that can provide novel ways of testing these hypotheses. Finally, we consider how this greater understanding of the phytobiome can facilitate sustainable disease management in agriculture by harnessing the potential of indigenous soil microbes.
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Hong, Shan, Hongling Jv, Xianfu Yuan, Jianjian Geng, Beibei Wang, Yan Zhao, Qing Wang, Rong Li, Zhongjun Jia, and Yunze Ruan. "Soil Organic Nitrogen Indirectly Enhances Pepper-Residue-Mediated Soil Disease Suppression through Manipulation of Soil Microbiome." Agronomy 12, no. 9 (August 31, 2022): 2077. http://dx.doi.org/10.3390/agronomy12092077.
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Banana Fusarium wilt-suppressive soils are effective against pathogen invasion, yet soil physicochemical factors responsible for conducive or suppressive behavior have not been reported. Here, we investigated the changes in banana biomass, disease incidence (DI), soil culturable microbes and physicochemical properties by incorporating pepper and banana residues into conducive and suppressive soils. Before the incorporation of any residues, the suppressive soil significantly increased banana biomass and decreased DI compared to the conducive soil. The biomass of the suppressive soil was significantly higher than that of the conducive soil after the incorporation of either pepper or banana residues. Compared with the control (CK), the incorporation of pepper residues to both soils significantly reduced DI, while banana residues had the opposite effect. Additionally, both conducive and suppressive soils supplemented with pepper residues significantly reduced the amounts of culturable Fusarium oxysporum and increased the amounts of beneficial Pseudomonas and Bacillus. The pepper residue extracts significantly inhibited the growth of F. oxysporum mycelium. Soil alkali-hydrolyzable nitrogen (AN) responded most strongly to residue application to suppressive soil. The AN factor was significantly and positively correlated with banana biomass; however, there was no direct and significant negative correlation with DI. Further analysis of the results showed that elevated AN content could stimulate the amounts of culturable Bacillus in the soil, and Bacillus antagonized the proliferation of pathogen and thus indirectly and effectively reduced banana DI. In conclusion, soil AN content can indirectly improve the disease suppression ability of pepper-residue-mediated suppressive soil by manipulating the soil microbiome.
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Simon, A., and K. Sivasithamparam. "Microbiological differences between soils suppressive and conducive of the saprophytic growth of Gaeumannomyces graminis var. tritici." Canadian Journal of Microbiology 34, no. 7 (July 1, 1988): 860–64. http://dx.doi.org/10.1139/m88-148.
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A soil acidified by ammonium sulphate following annual application of the fertilizer for 9 years was suppressive of the saprophytic growth of Gaeumannomyces graminis var. tritici in soil (pathogen suppressive). The same soil amended with lime was pathogen conducive. In natural field soil microbial respiration and the 'total' number of aerobic microorganisms were greater in the conducive than in the suppressive soil. In a soil-sandwich bioassay of the transferable suppression of saprophytic growth of the pathogen there were higher numbers of 'total' aerobic microorganisms, fluorescent pseudomonads, and Gram-negative organisms, but lower numbers of filamentous fungi and yeasts in the conducive than in the suppressive soil. It was estimated that Trichoderma spp. made up 71 and 34% of the total numbers of fungi counted in the suppressive and conducive soils, respectively. It is proposed that Trichoderma spp. played a major role in the transferable pathogen suppression in the suppressive soil.
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Wright, Peter J., Rebekah A. Frampton, Craig Anderson, and Duncan Hedderley. "Factors associated with soils suppressive to black scurf of potato caused by Rhizoctonia solani." New Zealand Plant Protection 75 (August 30, 2022): 31–49. http://dx.doi.org/10.30843/nzpp.2022.75.11761.
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Soils in which disease fails to develop despite pathogen presence are considered disease-suppressive. They offer sustainable, effective protection to plants against infection by soil-borne pathogens. Naturally disease-suppressive soils have been reported for diseases of a diverse range of agricultural crops worldwide yet the underlying mechanisms of disease suppression are still not completely understood. Two large greenhouse experiments, conducted during 2017/18 (Year 1) and 2018/19 (Year 2), determined that soils naturally suppressive to stem canker and black scurf of potato (caused by Rhizoctonia solani) are present in vegetable-arable cropping soils of the Auckland and Waikato regions of New Zealand. Soil was pre-treated with heat prior to inoculation with R. solani and compared with untreated and uninoculated controls to ascertain if stem canker and black scurf suppression was ‘general’, or ‘specific’ (i.e. transferable; possibly involving specific microorganisms). Rhizoctonia solani inoculation was also combined with transfer of one part test soil to nine parts of a known disease-conducive soil. Abiotic factors such as soil texture and organic matter content influenced black scurf incidence and severity. Soil microorganisms were also involved in disease suppression since black scurf incidence and severity markedly increased when they were eliminated or reduced by soil heat pre-treatment. Microbial profiling of the soils through sequencing revealed that taxa of geographically close soils of the same type had similar fungal and bacterial community structure and diversity even though they differed in their capacity to suppress black scurf. These results suggest that although the soil microbiome as a whole, was mainly responsible for soil disease suppressiveness, certain bacterial genera or species may play a role in black scurf suppression.
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Alabouvette, Claude. "Fusarium wilt suppressive soils: an example of disease-suppressive soils." Australasian Plant Pathology 28, no. 1 (1999): 57. http://dx.doi.org/10.1071/ap99008.
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Okalebo, Jane, Gary Y. Yuen, Rhae A. Drijber, Erin E. Blankenship, Cafer Eken, and John L. Lindquist. "Biological Suppression of Velvetleaf (Abutilon theophrasti) in an Eastern Nebraska Soil." Weed Science 59, no. 2 (June 2011): 155–61. http://dx.doi.org/10.1614/ws-d-10-00115.1.
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Weed-suppressive soils contain naturally occurring microorganisms that suppress a weed by inhibiting its growth, development, and reproductive potential. Increased knowledge of microbe–weed interactions in such soils could lead to the identification of management practices that create or enhance soil suppressiveness to weeds. Velvetleaf death and growth suppression was observed in a research field (fieldA) that was planted with high populations of velvetleaf, which may have developed via microbial mediated plant–soil feedback. Greenhouse studies were conducted with soil collected fromfieldA(soilA) to determine if it was biologically suppressive to velvetleaf. In one study, mortality of velvetleaf grown for 8 wk insoilAwas greatest (86%) and biomass was smallest (0.3 g plant−1) in comparison to soils collected from surrounding fields with similar structure and nutrient content, indicating that suppressiveness ofsoilAwas not likely caused by physical or chemical factors. WhensoilAwas autoclaved in another study, mortality of velvetleaf plants in the heat-treated soil was reduced to 4% compared to 55% for the untreated soil, thus suggesting that suppressiveness ofsoilAis biological in nature. A third set of experiments showed that suppressiveness to velvetleaf could be transferred to an autoclaved soil by amending the autoclaved soil with untreatedsoilA; this provided additional evidence for a biological basis for the effects ofsoilA.The suppressive condition in these greenhouse experiments was associated with high soil populations of fusaria.Fusarium lateritiumwas the most frequently isolated fungus from roots of diseased velvetleaf plants collected fromfieldA, and also was the most virulent when inoculated onto velvetleaf seedlings. Results of this research indicate that velvetleaf suppression can occur naturally in the field and thatF. lateritiumis an important cause of velvetleaf mortality infieldA.
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Aslam, Saman. "Non-pathogenic Fusarium oxysporum contributes in the biological suppression of pea wilt in disease suppressive soil." Pakistan Journal of Agricultural Sciences 59, no. 02 (January 1, 2022): 199–206. http://dx.doi.org/10.21162/pakjas/22.9093.
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Peas are growing all over the world as a leguminous crop due to high nutrients value. Fusarium wilt of peas is a destructive disease and causing deleterious loses in pea growing regions of the world. The fields were surveyed with disease incidence of Fusarium wilt in major pea growing areas. Fields with heavy pathogen infestation and natural disease suppressive were observed at District Sahiwal, Pakistan. The samples were collected to diagnose the disease and factors responsible in the suppression of disease. The results of soil physio-chemical properties showed no significant differences between diseased and suppressive soils. Pathogenicity assays both in-vitro and pot trial showed that suppressive soil has natural ability to suppress the disease. Furthermore, in-vitro and pot assays were designed with different soil treatments to investigate the factors responsible in the natural disease suppressiveness in suppressive soil. The results demonstrated that the mechanism involved in disease suppressive soil is biotic in nature. All isolated fungal strains from diseased and healthy roots of pea were subjected to biological assays to evaluate the virulence. The assays showed that isolate SAH09 is non-pathogenic Fusarium oxysporum which was isolated from the pea roots of suppressive soil. Isolate SAH09 was used in dual culturing technique and pot trial to evaluate the mycoparastism behavior against virulent pathogenic isolates SAH03, SAH05 and SAH10. Results concluded that isolate SAH09 of non-pathogenic Fusarium oxysporum has potential to suppress the growth of all isolates of pathogenic Fusarium and possibly play the role in natural disease suppression in suppressive soils
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Mazzola, Mark, and Yu-Huan Gu. "Wheat Genotype-Specific Induction of Soil Microbial Communities Suppressive to Disease Incited by Rhizoctonia solani Anastomosis Group (AG)-5 and AG-8." Phytopathology® 92, no. 12 (December 2002): 1300–1307. http://dx.doi.org/10.1094/phyto.2002.92.12.1300.
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The induction of disease-suppressive soils in response to specific cropping sequences has been demonstrated for numerous plant-pathogen systems. The role of host genotype in elicitation of the essential transformations in soil microbial community structure that lead to disease suppression has not been fully recognized. Apple orchard soils were planted with three successive 28-day cycles of specific wheat cultivars in the greenhouse prior to infestation with Rhizoctonia solani anastomosis group (AG)-5 or AG-8. Suppressiveness to Rhizoctonia root rot of apple caused by the introduced isolate of R. solani AG-5 was induced in a wheat cultivar-specific manner. Pasteurization of soils after wheat cultivation and prior to pathogen introduction eliminated the disease suppressive potential of the soil. Wheat cultivars that induced disease suppression enhanced populations of specific fluorescent pseudomonad genotypes with antagonistic activity toward R. solani AG-5 and AG-8, but cultivars that did not elicit a disease suppressive soil did not modify the antagonistic capacity of this bacterial community. When soils were infested prior to the initial wheat planting, all cultivars were uniformly susceptible to R. solani AG-8. However, when pathogen inoculum was added after three growth-cycles, wheat root infection during the fourth growth-cycle varied in a cultivar specific manner. The same wheat cultivar-specific response in terms of transformation of the fluorescent pseudomonad community and subsequent suppression of Rhizoctonia root rot of apple was observed in three different orchard soils. These results demonstrate the importance of host genotype in modification of indigenous saprophytic microbial communities and suggest an important role for host genotype in the success of biological control.
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Shen, Zongzhuan, Linda S. Thomashow, Yannan Ou, Chengyuan Tao, Jiabao Wang, Wu Xiong, Hongjun Liu, Rong Li, Qirong Shen, and George A. Kowalchuk. "Shared Core Microbiome and Functionality of Key Taxa Suppressive to Banana Fusarium Wilt." Research 2022 (September 16, 2022): 1–15. http://dx.doi.org/10.34133/2022/9818073.
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Microbial contributions to natural soil suppressiveness have been reported for a range of plant pathogens and cropping systems. To disentangle the mechanisms underlying suppression of banana Panama disease caused by Fusarium oxysporum f. sp. cubense tropical race 4 (Foc4), we used amplicon sequencing to analyze the composition of the soil microbiome from six separate locations, each comprised of paired orchards, one potentially suppressive and one conducive to the disease. Functional potentials of the microbiomes from one site were further examined by shotgun metagenomic sequencing after soil suppressiveness was confirmed by greenhouse experiments. Potential key antagonists involved in disease suppression were also isolated, and their activities were validated by a combination of microcosm and pot experiments. We found that potentially suppressive soils shared a common core community with relatively low levels of F. oxysporum and relatively high proportions of Myxococcales, Pseudomonadales, and Xanthomonadales, with five genera, Anaeromyxobacter, Kofleria, Plesiocystis, Pseudomonas, and Rhodanobacter being significantly enriched. Further, Pseudomonas was identified as a potential key taxon linked to pathogen suppression. Metagenomic analysis showed that, compared to the conducive soil, the microbiome in the disease suppressive soil displayed a significantly greater incidence of genes related to quorum sensing, biofilm formation, and synthesis of antimicrobial compounds potentially active against Foc4. We also recovered a higher frequency of antagonistic Pseudomonas isolates from disease suppressive experimental field sites, and their protective effects against banana Fusarium wilt disease were demonstrated under greenhouse conditions. Despite differences in location and soil conditions, separately located suppressive soils shared common characteristics, including enrichment of Myxococcales, Pseudomonadales, and Xanthomonadales, and enrichment of specific Pseudomonas populations with antagonistic activity against the pathogen. Moreover, changes in functional capacity toward an increase in quorum sensing, biofilm formation, and antimicrobial compound synthesizing involve in disease suppression.
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Yin, Bei, Lea Valinsky, Xuebiao Gao, J. Ole Becker, and James Borneman. "Identification of Fungal rDNA Associated with Soil Suppressiveness Against Heterodera schachtii Using Oligonucleotide Fingerprinting." Phytopathology® 93, no. 8 (August 2003): 1006–13. http://dx.doi.org/10.1094/phyto.2003.93.8.1006.
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To understand the nature of a soil with suppressiveness against Heterodera schachtii, an rDNA analysis was used to identify fungi associated with H. schachtii cysts obtained from soils possessing various levels of suppressiveness. Because H. schachtii cysts isolated from these suppressive soils can transfer this beneficial property to nonsuppressive soils, analysis of the microorganisms associated with the cysts should lead to the identification of the causal organisms. Five soil treatments, generated by mixing different amounts of suppressive and fumigation-induced nonsuppressive soils, were infested with second-stage juveniles of H. schachtii and cropped with mustard-greens. Fungi were identified through an rDNA analysis termed oligonucleotide fingerprinting of ribosomal RNA genes (OFRG). Cysts obtained from soil mixtures consisting of 10 and 100% suppressive soil predominantly contained fungal rDNA with high sequence identity to Dactylella oviparasitica. The dominant fungal rDNA in the cysts isolated from the soil mixtures composed of 0.1 and 1% suppressive soil had high sequence identity to Fusarium oxysporum. Polymerase chain reaction (PCR) amplifications performed with sequence-selective primers corroborated the treatment-specific distribution of rDNA clones obtained by the OFRG analysis. When these sequence-selective PCR primers were used to examine H. schachtii cysts from biocidal soil treatments that produced various levels of suppressiveness, only the D. oviparasitica-like rDNA was consistently identified in the highly suppressive soils.
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Simon, A., and K. Sivasithamparam. "The soil environment and the suppression of saprophytic growth of Gaeumannomyces graminis var. tritici." Canadian Journal of Microbiology 34, no. 7 (July 1, 1988): 865–70. http://dx.doi.org/10.1139/m88-149.
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The effect of the soil environment on the transferable suppression of the saprophytic growth of Gaeumannomyces graminis var. tritici (pathogen suppression) was studied in a field soil acidified to pH 4.3 by annual treatment with ammonium sulphate for 9 years and in the same soil further amended with a single application of lime (pH 5.4). Pathogen suppression and the activity of Trichoderma spp. were greater when (i) the unlimed (pathogen-suppressive) soil was added at a rate of 1% (w/w) to the same soil treated with γ-radiation than when added at the same rate to the irradiated limed soil; (ii) the limed (pathogen-conducive) soil was added at 1% (w/w) to the irradiated unlimed soil than when added at the same rate to the irradiated limed soil. Pathogen suppression and the activity of Trichoderma spp. were increased in both soils with the addition of an antibacterial agent. The saprophytic growth of G. graminis var. tritici was reduced in the unsterile pathogen-suppressive but not in the pathogen-conducive soil, following the addition of inoculum of T. koningii. It is proposed that both the abiotic and biotic environments of soil can influence the expression of transferable pathogen suppression which, in the soils tested, is related to the activity of Trichoderma spp.
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Mazzola, Mark, David M. Granatstein, Don C. Elfving, Kent Mullinix, and Yu-Huan Gu. "Cultural Management of Microbial Community Structure to Enhance Growth of Apple in Replant Soils." Phytopathology® 92, no. 12 (December 2002): 1363–66. http://dx.doi.org/10.1094/phyto.2002.92.12.1363.
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Apple replant disease typically is managed through pre-plant application of broad-spectrum soil fumigants including methyl bromide. The impending loss or restricted use of soil fumigants and the needs of an expanding organic tree fruit industry necessitate the development of alternative control measures. The microbial community resident in a wheat field soil was shown to suppress components of the microbial complex that incites apple replant disease. Pseudomonas putida was the primary fluorescent pseudomonad recovered from suppressive soil, whereas Pseudomonas fluorescens bv. III was dominant in a conducive soil; the latter developed within 3 years of orchard establishment at the same site. In greenhouse studies, cultivation of wheat in replant orchard soils prior to planting apple suppressed disease development. Disease suppression was induced in a wheat cultivar-specific manner. Wheat cultivars that enhanced apple seedling growth altered the dominant fluorescent pseudo-monad from Pseudomonas fluorescens bv. III to Pseudomonas putida. The microbial community resident in replant orchard soils after growing wheat also was suppressive to an introduced isolate of Rhizoctonia solani anastomosis group 5, which causes root rot of apple. Incorporation of high glucosinolate containing rapeseed (‘Dwarf Essex’) meal also enhanced growth of apple in replant soils through suppression of Rhizoc-tonia spp., Cylindrocarpon spp., and Pratylenchus penetrans. Integration of these methods will require knowledge of the impact of the biofumigant component on the wheat-induced disease-suppressive microbial community. Implementation of these control strategies for management of apple replant disease awaits confirmation from ongoing field validation trials.
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May, FE, and JE Ash. "An Assessment of the Allelopathic Potential of Eucalyptus." Australian Journal of Botany 38, no. 3 (1990): 245. http://dx.doi.org/10.1071/bt9900245.
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Previous studies have shown that various Eucalyptus species can yield allelopathic chemicals which may be effective in suppressing understorey vegetation. However, the techniques employed in many studies do not resemble natural ecological processes. This study used germination of Lolium and growth of Lolium, Lemna, Eucalyptus and Acacia to test for allelopathy. Extraction techniques mimicked typical daily rainfall rates upon quantities of foliage, leaf litter and bark litter that are typically encountered in forests; root leachates were obtained hydroponically; stemflow was obtained following rainfall; soils were leached with water; and volatiles from leaves were studied in an enclosed chamber. Fresh intact leaves caused little growth suppression, in contrast to coarsely chopped leaves and extracted leaf essential oils which were both highly suppressive. Whole leaf litter, shed bark and, especially, stemflow yielded suppressive leachates. Evaporative concentration of leachates in soils was demonstrated, which increased their inhibitory effect. It is apparent that allelopathy must be considered in relation to rainfall and the soil water balance. Decay was shown to reduce the allelopathic effects of leaf and bark litter leachates but some inhibitory chemicals remained after 5 months. It was concluded that allelopathy is likely to be a cause of understorey suppression by Eucalyptus species especially in drier climates.
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Wang, Quanzhi, Limin Zhou, Han Jin, Bingcheng Cong, Hua Yang, and Shimei Wang. "Investigating the Responses of Microbial Communities to Banana Fusarium Wilt in Suppressive and Conducive Soils Based on Soil Particle-Size Differentiation." Agronomy 12, no. 2 (January 18, 2022): 229. http://dx.doi.org/10.3390/agronomy12020229.
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The microbiota plays a primary role in inhibiting plant pathogens in the soils. However, the correlation between soil particles and local microbial communities has not been fully confirmed. In this study, we contrasted the different assemblages of microbial communities between suppressive and conducive soils via the differentiation of soil particle-size fractions (PSFs). We further extracted the direct and indirect interactive associations among the soil biotic and abiotic factors by using samples from two continuous banana cropping systems. Notable differences were shown in PSF composition, biological traits (microbial communities and enzyme patterns) and physiochemical parameters between suppressive and conducive soils among the different soil fractions. For example, compared with conducive soils, suppressive soils have higher nutrient contents, fungal abundance and diversity and enzyme activities, and the extent of these differences was explored for fractions of different sizes. Moreover, the microbial taxonomic composition strongly varied between disease-suppressive and disease-conducive soils. For instance, there were significant differences in the relative abundance among key microbiology communities, such as Actinobacteria, Firmicutes, Bacteroidetes, Proteobacteria and Ascomycota, especially for antagonistic microorganisms (i.e., Streptomyces, Pseudomonas, Trichoderma, etc.) across various soil fractions. In addition, structural equation modeling (SEM) showed that the complex associations among soil PSFs, physiochemical parameters and microbial communities were mediated by multiple pathways, which then drive the soil enzyme activities and may further influence the suppressiveness of the soil. These results demonstrate that the resident microbial communities in specific soil particles may play a crucial role in the development of soil suppressiveness against banana Fusarium wilt disease.
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Inderbitzin, Patrik, Judson Ward, Alexandra Barbella, Natalie Solares, Dmitriy Izyumin, Prabir Burman, Dan O. Chellemi, and Krishna V. Subbarao. "Soil Microbiomes Associated with Verticillium Wilt-Suppressive Broccoli and Chitin Amendments are Enriched with Potential Biocontrol Agents." Phytopathology® 108, no. 1 (January 2018): 31–43. http://dx.doi.org/10.1094/phyto-07-17-0242-r.
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Two naturally infested Verticillium wilt-conducive soils from the Salinas Valley of coastal California were amended with disease-suppressive broccoli residue or crab meal amendments, and changes to the soil prokaryote community were monitored using Illumina sequencing of a 16S ribosomal RNA gene library generated from 160 bulk soil samples. The experiment was run in a greenhouse, twice, with eggplant as the Verticillium wilt-susceptible host. Disease suppression, plant height, soil microsclerotia density, and soil chitinase activity were assessed at the conclusion of each experiment. In soil with high microsclerotia density, all amendments significantly reduced Verticillium wilt severity and microsclerotia density, and increased soil chitinase activity. Plant height was increased only in the broccoli-containing treatments. In total, 8,790 error-corrected sequence variants representing 1,917,893 different sequences were included in the analyses. The treatments had a significant impact on the soil microbiome community structure but measures of α diversity did not vary between treatments. Community structure correlated with disease score, plant height, microsclerotia density, and soil chitinase activity, suggesting that the prokaryote community may affect the disease-related response variables or vice versa. Similarly, the abundance of 107 sequence variants correlated with disease-related response variables, which included variants from genera with known antagonists of filamentous fungal plant pathogens, such as Pseudomonas and Streptomyces. Overall, genera with antifungal antagonists were more abundant in amended soils than unamended soils, and constituted up to 8.9% of all sequences in broccoli+crabmeal-amended soil. This study demonstrates that substrate-mediated shifts in soil prokaryote communities are associated with the transition of Verticillium wilt-conducive soils to Verticillium wilt-suppressive soils, and suggests that soils likely harbor numerous additional antagonists of fungal plant pathogens that contribute to the biological suppression of plant disease.
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Barnett, Stephen J., David K. Roget, and Maarten H. Ryder. "Suppression of Rhizoctonia solani AG-8 induced disease on wheat by the interaction between Pantoea, Exiguobacterium, and Microbacteria." Soil Research 44, no. 4 (2006): 331. http://dx.doi.org/10.1071/sr05113.
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Rhizoctonia solani AG-8 is a major wheat root pathogen; however, soils can become suppressive to the expression of disease under intensive cropping with retention of crop residues. This is in part due to the action of soil microorganisms. A step-wise approach was used to determine which microorganisms contributed to suppression of R. solani induced disease in a disease-suppressive soil. Using wheat-soil-pathogen bioassays it was determined that the interaction between 3 phylogenetically diverse groups of bacteria, Pantoea agglomerans, Exiguobacterium acetylicum, and Microbacteria (family Microbacteriaceae), was a major contributor to disease suppression. Inoculation of a sterilised soil with the combination of these groups resulted in greatly increased seedling shoot dry weight and reduced infection compared with diseased control plants with no bacterial inoculation, or inoculated with individual types of bacteria. These groups, however, did not reduce levels of pathogen DNA, although inoculation with suppressive soil (at 10% w/w) did reduce pathogen DNA. Root associated P. agglomerans and E. acetylicum promoted the growth of infected wheat plants and soil associated Microbacteria reduced root infection by R. solani.
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Yin, Bei, Lea Valinsky, Xuebiao Gao, J. Ole Becker, and James Borneman. "Bacterial rRNA Genes Associated with Soil Suppressiveness against the Plant-Parasitic Nematode Heterodera schachtii." Applied and Environmental Microbiology 69, no. 3 (March 2003): 1573–80. http://dx.doi.org/10.1128/aem.69.3.1573-1580.2003.
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ABSTRACT The goal of this study was to identify bacteria involved in soil suppressiveness against the plant-parasitic nematode Heterodera schachtii. Since H. schachtii cysts isolated from the suppressive soil can transfer this beneficial property to nonsuppressive soils, analysis of the cyst-associated microorganisms should lead to the identification of the causal organisms. Our experimental approach was to identify bacterial rRNA genes (rDNA) associated with H. schachtii cysts obtained from soil mixtures with various levels of suppressiveness. We hypothesized that we would be able to identify bacteria involved in the suppressiveness by correlating population shifts with differing levels of suppressiveness. Soil treatments containing different amounts of suppressive and fumigation-induced nonsuppressive soils exhibited various levels of suppressiveness after two nematode generations. The 10%-suppressive-soil treatment contained numbers of eggs per gram of soil similar to those of the 100%-suppressive-soil treatment, indicating that the suppressive factor(s) had been transferred. Bacterial rDNA associated with H. schachtii cysts were identified using a culture-independent method termed oligonucleotide fingerprinting of rRNA genes. Bacteria from five major taxonomic groups (Actinobacteria, Cytophaga-Flexibacter-Bacteroides, α-Proteobacteria, β-Proteobacteria, and γ-Proteobacteria) were identified. Three bacterial rDNA groups contained clones that were more prevalent in the highly suppressive soil treatments than in the less suppressive treatments, indicating a potential involvement in the H. schachtii suppressiveness. When these three groups were examined with specific PCR analyses performed on H. schachtii cysts that developed in soils treated with three biocidal compounds, only one bacterial rDNA group with moderate to high sequence identity to rDNA from several Rhizobium species and uncultured α-proteobacterial clones was consistently associated with the highly suppressive treatments. A quantitative PCR analysis confirmed the association of this Rhizobium-like rDNA group with the H. schachtii suppressiveness.
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Rimé, Delphine, Sylvie Nazaret, François Gourbière, Patrice Cadet, and Yvan Moënne-Loccoz. "Comparison of Sandy Soils Suppressive or Conducive to Ectoparasitic Nematode Damage on Sugarcane." Phytopathology® 93, no. 11 (November 2003): 1437–44. http://dx.doi.org/10.1094/phyto.2003.93.11.1437.
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Two South African sandy soils, one suppressive and the other conducive to ectoparasitic nematode damage on monoculture sugarcane, were compared. Analysis of field transects indicated that the suppressive soil displayed a comparatively higher population of the weak ectoparasite Helicotylenchus dihystera, whose predominance among ectoparasitic nematodes is known to limit yield loss caused by more virulent phytonematodes. Soil type was identical at both sites (entisols), but the suppressive soil had a higher organic matter content and a lower pH, which correlated with H. dihystera population data. In contrast, microclimatic differences between the two field sites were unlikely to be responsible for the suppressive or conducive status of the soils, as shown in a greenhouse experiment. The two soils exhibited a bacterial community of the same size but with different genetic structures, as indicated by automated ribosomal intergenic spacer analysis (RISA). The number of culturable fluorescent pseudomonads was higher for the conducive soil, probably because extensive root damage caused by ectoparasitic nematodes favored proliferation of these bacteria. This study shows that apparently small differences in soil composition between fields located in the same climatic area and managed similarly can translate into contrasted nematode communities, ectoparasitic nematode damage levels, and sugarcane yields.
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Simon, A., and K. Sivasithamparam. "Interactions among Gaeumannomyces graminis var. tritici, Trichoderma koningii, and soil bacteria." Canadian Journal of Microbiology 34, no. 7 (July 1, 1988): 871–76. http://dx.doi.org/10.1139/m88-150.
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Interactions among Gaeumannomyces graminis var. tritici, Trichoderma koningii, and soil bacteria were studied in vitro and in soils suppressive and conducive of the saprophytic growth of G. graminis var. tritici. Fifty-four percent of bacteria isolated from the suppressive soil and 10% from the conducive soil were antagonistic to G. graminis var. tritici in vitro. The reduction in the growth of T. koningii in vitro by metabolite(s) produced in pure culture by soil bacteria was 14 and 28% for the bacteria isolated from the suppressive and conducive soil, respectively. Metabolite(s) produced by T. koningii in pure culture inhibited the growth in vitro of 8 and 65% of the bacteria isolated from the suppressive and conducive soils, respectively. All isolates of Trichoderma tested produced metabolite(s) that inhibited growth of G. graminis var. tritici in pure culture. The metabolite(s) produced by one isolate of T. koningii inhibited growth of all isolates of Trichoderma in vitro. Trichoderma koningii suppressed saprophytic growth of G. graminis var. tritici in irradiated conducive soil in the absence but not in the presence of bacteria isolated from the same soil. The results suggest that the suppressive soil may be more suppressive of the saprophytic growth of G. graminis var. tritici and less suppressive of the growth of T. koningii than the conducive soil.
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Zhang, Na, Chengzhi Zhu, Zongzhuan Shen, Chengyuan Tao, Yannan Ou, Rong Li, Xuhui Deng, Qirong Shen, and Francisco Dini-Andreote. "Partitioning the Effects of Soil Legacy and Pathogen Exposure Determining Soil Suppressiveness via Induced Systemic Resistance." Plants 11, no. 21 (October 23, 2022): 2816. http://dx.doi.org/10.3390/plants11212816.
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Beneficial host-associated bacteria can assist plant protection against pathogens. In particular, specific microbes are able to induce plant systemic resistance. However, it remains largely elusive which specific microbial taxa and functions trigger plant immune responses associated with disease suppression. Here, we experimentally studied this by setting up two independent microcosm experiments that differed in the time at which plants were exposed to the pathogen and the soil legacy (i.e., soils with historically suppressive or conducive). Overall, we found soil legacy effects to have a major influence on disease suppression irrespective of the time prior to pathogen exposure. Rhizosphere bacterial communities of tomato plants were significantly different between the two soils, with potential beneficial strains occurring at higher relative abundances in the suppressive soil. Root transcriptome analysis revealed the soil legacy to induce differences in gene expression, most importantly, genes involved in the pathway of phenylpropanoid biosynthesis. Last, we found genes in the phenylpropanoid biosynthesis pathway to correlate with specific microbial taxa, including Gp6, Actinomarinicola, Niastella, Phaeodactylibacter, Longimicrobium, Bythopirellula, Brevundimonas, Ferruginivarius, Kushneria, Methylomarinovum, Pseudolabrys, Sphingobium, Sphingomonas, and Alterococcus. Taken together, our study points to the potential regulation of plant systemic resistance by specific microbial taxa, and the importance of soil legacy on disease incidence and eliciting plant-defense mechanisms.
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Kasuya, Masahiro, Andriantsoa R. Olivier, Yoko Ota, Motoaki Tojo, Hitoshi Honjo, and Ryo Fukui. "Induction of Soil Suppressiveness Against Rhizoctonia solani by Incorporation of Dried Plant Residues into Soil." Phytopathology® 96, no. 12 (December 2006): 1372–79. http://dx.doi.org/10.1094/phyto-96-1372.
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Suppressive effects of soil amendment with residues of 12 cultivars of Brassica rapa on damping-off of sugar beet were evaluated in soils infested with Rhizoctonia solani. Residues of clover and peanut were tested as noncruciferous controls. The incidence of damping-off was significantly and consistently suppressed in the soils amended with residues of clover, peanut, and B. rapa subsp. rapifera ‘Saori’, but only the volatile substance produced from water-imbibed residue of cv. Saori exhibited a distinct inhibitory effect on mycelial growth of R. solani. Nonetheless, disease suppression in such residue-amended soils was diminished or nullified when antibacterial antibiotics were applied to the soils, suggesting that proliferation of antagonistic bacteria resident to the soils were responsible for disease suppression. When the seed (pericarps) colonized by R. solani in the infested soil without residues were replanted into the soils amended with such residues, damping-off was suppressed in all cases. In contrast, when seed that had been colonized by microorganisms in the soils containing the residues were replanted into the infested soil, damping-off was not suppressed. The evidence indicates that the laimosphere, but not the spermosphere, is the site for the antagonistic microbial interaction, which is the chief principle of soil suppressiveness against Rhizoctonia damping-off.
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Rosenzweig, Noah, James M. Tiedje, John F. Quensen, Qingxiao Meng, and Jianjun J. Hao. "Microbial Communities Associated with Potato Common Scab-Suppressive Soil Determined by Pyrosequencing Analyses." Plant Disease 96, no. 5 (May 2012): 718–25. http://dx.doi.org/10.1094/pdis-07-11-0571.
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Potato common scab, caused by Streptomyces spp., is an annual production problem for potato growers, and not effectively controlled by current methods. A field with naturally occurring common scab suppression has been identified in Michigan, and confirmed to have a biological basis for this disease suppression. This field and an adjacent scab nursery conducive to disease were studied using pyrosequencing to compare the two microbial communities. Total DNA was extracted from both the disease-conducive and -suppressive soils. A phylogenetically taxon-informative region of the 16S rRNA gene was used to establish operational taxonomic units (OTUs) to characterize bacterial community richness and diversity. In total, 1,124 OTUs were detected and 565 OTUs (10% dissimilarity) were identified in disease-conducive soil and 859 in disease-suppressive soil, including 300 shared both between sites. Common phyla based on relative sequence abundance were Acidobacteria, Proteobacteria, and Firmicutes. Sequences of Lysobacter were found in significantly higher numbers in the disease-suppressive soil, as were sequences of group 4 and group 6 Acidobacteria. The relative abundance of sequences identified as the genus Bacillus was significantly higher by an order of magnitude in the disease-conducive soil.
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Zhou, Cheng, Zhongyou Ma, Xiaoming Lu, Lin Zhu, and Jianfei Wang. "Phenolic Acid-Degrading Consortia Increase Fusarium Wilt Disease Resistance of Chrysanthemum." Agronomy 10, no. 3 (March 12, 2020): 385. http://dx.doi.org/10.3390/agronomy10030385.
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Soil microbial community changes imposed by the cumulative effects of root-secreted phenolic acids (PAs) promote soil-borne pathogen establishment and invasion under monoculture systems, but the disease-suppressive soil often exhibits less soil-borne pathogens compared with the conducive soil. So far, it remains poorly understood whether soil disease suppressiveness is associated with the alleviated negative effects of PAs, involving microbial degradation. Here, the long-term monoculture particularly shaped the rhizosphere microbial community, for example by the enrichment of beneficial Pseudomonas species in the suppressive soil and thus enhanced disease-suppressive capacity, however this was not observed for the conducive soil. In vitro PA-degradation assays revealed that the antagonistic Pseudomonas species, together with the Xanthomonas and Rhizobium species, significantly increased the efficiency of PA degradation compared to single species, at least partially explaining how the suppressive soil accumulated lower PA levels than the conducive soil. Pot experiments further showed that this consortium harboring the antagonistic Pseudomonas species can not only lower PA accumulation in the 15-year conducive soils, but also confer stronger Fusarium wilt disease suppression compared with a single inoculum with the antagonistic bacteria. Our findings demonstrated that understanding microbial community functions, beyond the single direct antagonism, facilitated the construction of active consortia for preventing soil-borne pathogens under intensive monoculture.
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Min, Yu Yu, and Koki Toyota. "Suppression of Meloidogyne incognita in different agricultural soils and possible contribution of soil fauna." Nematology 15, no. 4 (2013): 459–68. http://dx.doi.org/10.1163/15685411-00002693.
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A total of 12 soils collected from different agricultural fields, having different backgrounds of organic input, were evaluated for their suppressive potential against Meloidogyne incognita. Second-stage juveniles (J2) of M. incognita were inoculated into the soils and their survival was evaluated. The number of M. incognita J2 5 days after inoculation differed depending on soil and was significantly lower in two soils, suggesting higher suppressiveness against M. incognita in these soils. This was confirmed by an experiment using tomato as a test plant, in which the gall formation was significantly lower in the two soils than in other soils. To estimate the contribution of below-ground biota to the suppressiveness, numbers of nematodes (predator, omnivore, bacterivore and fungivore) and other soil fauna such as tardigrades and rotifers, were counted. Some soil chemical and biological properties were also measured. Results from multiple linear regression analysis suggested that the number of rotifers, microbial activity, soil pH and total C may be involved in the suppression. The relationship between the suppressiveness and soil chemical and biological parameters is discussed.
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Kremer, Robert J., and Jianmei Li. "Developing weed-suppressive soils through improved soil quality management." Soil and Tillage Research 72, no. 2 (August 2003): 193–202. http://dx.doi.org/10.1016/s0167-1987(03)00088-6.
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Shimizu, Yukari, Daiki Sagiya, Mariko Matsui, and Ryo Fukui. "Zonal Soil Amendment with Simple Sugars to Elevate Soil C/N Ratios as an Alternative Disease Management Strategy for Rhizoctonia Damping-off of Sugar Beet." Plant Disease 102, no. 7 (July 2018): 1434–44. http://dx.doi.org/10.1094/pdis-09-16-1279-re.
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Effects of monosaccharide-amended soils on suppression of Rhizoctonia damping-off of sugar beet were compared under controlled experiments. Suppressive effects of glucose, fructose, sorbose, and xylose were significantly (P < 0.001) greater than that of galactose or mannose but the effect of sorbose was reduced by soil treatments with antibiotics. Saprotrophic growth of Rhizoctonia solani in the laimosphere also was suppressed by glucose, fructose, sorbose, and xylose, whereas only sorbose repressed pericarp colonization. Sugar alcohols (mannitol, sorbitol, and xylitol) neither suppressed Rhizoctonia damping-off nor halted the saprotrophic growth of the pathogen. Seed germination was not affected by any of these six monosaccharides, whereas galactose and mannose inhibited seedling emergence significantly (P < 0.001) compared with the nontreated control or other monosaccharides. Soil fertilization with inorganic nitrogen at a C/N ratio of 20:1 negated the suppressive effects of glucose and fructose on both damping-off and saprotrophic colonization but improved seedling growth in carbonized soils. Obviously, microbial competition for mineral nitrogen was responsible for disease suppression; however, it delayed seedling growth after emergence. This paradox was resolved by adding glucose to the top 1-cm surface-soil zone at a C/N ratio of 50:1 or 125:1. This protected the laimosphere, resulting in effective disease suppression while complementarily enhancing seedling growth.
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HO, W., L. CHERN, and W. KO. "Pseudomonas Solanacearum-suppressive soils in Taiwan." Soil Biology and Biochemistry 20, no. 4 (1988): 489–92. http://dx.doi.org/10.1016/0038-0717(88)90063-6.
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Goh, Yit Kheng, Muhammad Zarul Hanifah Md Zoqratt, You Keng Goh, Qasim Ayub, and Adeline Su Yien Ting. "Determining Soil Microbial Communities and Their Influence on Ganoderma Disease Incidences in Oil Palm (Elaeis guineensis) via High-Throughput Sequencing." Biology 9, no. 12 (November 27, 2020): 424. http://dx.doi.org/10.3390/biology9120424.
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Basal stem rot (BSR), caused by Ganoderma boninense, is the most devastating oil palm disease in South East Asia, costing US$500 million annually. Various soil physicochemical parameters have been associated with an increase in BSR incidences. However, very little attention has been directed to understanding the relationship between soil microbiome and BSR incidence in oil palm fields. The prokaryotic and eukaryotic microbial diversities of two coastal soils, Blenheim soil (Typic Quartzipsamment—calcareous shell deposits, light texture) with low disease incidence (1.9%) and Bernam soil (Typic Endoaquept—non-acid sulfate) with high disease incidence (33.1%), were determined using the 16S (V3–V4 region) and 18S (V9 region) rRNA amplicon sequencing. Soil physicochemical properties (pH, electrical conductivity, soil organic matter, nitrogen, phosphorus, cation exchange capacity, exchangeable cations, micronutrients, and soil physical parameters) were also analyzed for the two coastal soils. Results revealed that Blenheim soil comprises higher prokaryotic and eukaryotic diversities, accompanied by higher pH and calcium content. Blenheim soil was observed to have a higher relative abundance of bacterial taxa associated with disease suppression such as Calditrichaeota, Zixibacteria, GAL15, Omnitrophicaeota, Rokubacteria, AKYG587 (Planctomycetes), JdFR-76 (Calditrichaeota), and Rubrobacter (Actinobacteria). In contrast, Bernam soil had a higher proportion of other bacterial taxa, Chloroflexi and Acidothermus (Actinobacteria). Cercomonas (Cercozoa) and Calcarisporiella (Ascomycota) were eukaryotes that are abundant in Blenheim soil, while Uronema (Ciliophora) and mammals were present in higher abundance in Bernam soil. Some of the bacterial taxa have been reported previously in disease-suppressive and -conducive soils as potential disease-suppressive or disease-inducible bacteria. Furthermore, Cercomonas was reported previously as potential bacterivorous flagellates involved in the selection of highly toxic biocontrol bacteria, which might contribute to disease suppression indirectly. The results from this study may provide valuable information related to soil microbial community structures and their association with soil characteristics and soil susceptibility to Ganoderma.
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Dignam, B. E. A., M. O'Callaghan, L. M. Condron, J. M. Raaijmakers, G. A. Kowalchuk, and S. A. Wakelin. "A bioassay to compare the disease suppressive capacity of pasture soils." New Zealand Plant Protection 68 (January 8, 2015): 151–59. http://dx.doi.org/10.30843/nzpp.2015.68.5834.
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Dynamic pathogen complexes can develop under pastures thereby substantially reducing potential productivity Suppression of such pathogen complexes is therefore of great importance and bioassays can quantify disease suppression in soils This study describes the development of a pasturerelevant system Rhizoctonia solani AG 21 induced dampingoff (wirestem) of kale (Brassica oleracea) As kale is not a component of traditional ryegrass clover pasture swards the assay allows assessment of general disease suppression considered more enduring in multiplehostmultiplepathogen systems A pathogenic Rhizoctonia solani isolate was obtained from New Zealand pastoral soil Inoculation of soils with this isolate resulted in a level of dampingoff disease comparable to that induced by reference Rhizoctonia solani isolate Rs0432 Significantly different levels of inoculuminduced disease incidence and progression were found in four distinct pastoral soils In combination with soil physicochemical data and environmental DNA approaches this bioassay can be used to further advance understanding of the influence of farm management practices on disease suppression in pasture soils
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O’Connor, Patrick, Maria Manjarrez, and Sally E. Smith. "The fate and efficacy of benomyl applied to field soils to suppress activity of arbuscular mycorrhizal fungi." Canadian Journal of Microbiology 55, no. 7 (July 2009): 901–4. http://dx.doi.org/10.1139/w09-035.
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A systematic application of the fungicide benomyl was used to follow up the suppression of arbuscular mycorrhizal (AM) colonization and to determine its fungitoxic activity and persistence at different depths. Repeated applications of benomyl reduced AM colonization mainly in the upper 0–4 cm layer of the treated soils. Furthermore, AM colonization decreased with soil depth. The activity and persistence of this fungicide was reduced over small changes in depth in the first 10 cm of the soil profile beneath a semiarid herbland at Brookfield Conservation Park (South Australia). Repeated applications of the fungicide only slightly increased the levels of toxicity in the soils, probably because of biodegradation of the fungicide in soils with a recent history of exposure to the fungicide. The decline in fungicide activity at depth was correlated with a decline in the suppressive effect of the fungicide on the activity of AM fungi.
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Latif, Sajid, Saliya Gurusinghe, Paul A. Weston, William B. Brown, Jane C. Quinn, John W. Piltz, and Leslie A. Weston. "Performance and weed-suppressive potential of selected pasture legumes against annual weeds in south-eastern Australia." Crop and Pasture Science 70, no. 2 (2019): 147. http://dx.doi.org/10.1071/cp18458.
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Mixed farming systems have traditionally incorporated subterranean clover (Trifolium subterraneum L.) and lucerne (Medicago sativa L.) as key components of the pasture phase across south-eastern Australia. However, poor adaptation of subterranean clover to acidic soils, insufficient and inconsistent rainfall, high input costs, soil acidification and the emergence of herbicide-resistant weeds have reduced efficacy of some traditional clover species in recent years. To overcome these challenges, numerous novel pasture species have been selectively improved and released for establishment in Australia. Despite their suitability to Australian climate and soils, limited knowledge exists regarding their weed-suppressive ability in relation to establishment and regeneration. Field trials were therefore conducted over 3 years in New South Wales to evaluate the suppressive potential of selected pasture legume species and cultivars as monocultures and in mixed stands against dominant annual pasture weeds. Pasture and weed biomass varied significantly between pasture species when sown as monocultures, but mixtures of several species did not differ with regard to establishment and subsequent weed infestation. Arrowleaf clover (T. vesiculosum Savi.) and biserrula (Biserrula pelecinus L.) cv. Casbah showed improved stand establishment, with higher biomass and reduced weed infestation compared with other pasture species. Generally, weed suppression was positively correlated with pasture biomass; however, yellow serradella (Ornithopus compressus L.) cv. Santorini exhibited greater weed suppression than other pasture legumes while producing lower biomass, thereby suggesting a mechanism other than competition for resources affecting weed-suppressive ability. Over the period 2015–17, arrowleaf clover and biserrula cv. Casbah were generally the most consistent annual pasture legumes with respect to yearly regeneration and suppression of annual pasture weed species.
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Shoaf, Nathan, Lori Hoagland, and Daniel S. Egel. "Suppression of Phytophthora Blight in Sweet Pepper Depends on Biochar Amendment and Soil Type." HortScience 51, no. 5 (May 2016): 518–24. http://dx.doi.org/10.21273/hortsci.51.5.518.
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Phytophthora blight has become one of the most serious threats to the vegetable industry. Managing this disease is challenging, because the oomycete pathogen responsible, Phytophthora capsici, can move rapidly through crop fields, has a wide host range, is resistant to many commonly used fungicides, and produces resilient spores that can survive in soil for up to 10 years. Recent studies have demonstrated that biochar amendments can suppress infection by many soil-borne pathogens—indicating that these amendments could have the potential to help control phytophthora blight. In this study, greenhouse trials were conducted to determine whether two commercially available biochar amendments could suppress P. capsici infection in sweet bell pepper (Capsicum annuum) using three naturally infested field soils. Soil biological and chemical assays were conducted to evaluate whether potential changes induced by biochar amendments were correlated with suppressive activity. Amending soil with a biochar product that included a proprietary mix of beneficial microorganisms and enriched substrates resulted in lower soil P. capsici abundance in all soils, and lower percent root infection in two of the soils tested. This product also resulted in higher soil pH, and lower soil nitrogen availability and leaf chlorophyll content. The other biochar product did not suppress P. capsici, and had few effects on soil chemical and biological properties. Results of this study indicate that some commercially available biochar amendments have the potential to help mediate phytophthora blight, but further trials are needed to confirm that suppressive effects will be observed in field trials. Additional research is also recommended to identify the mechanisms regulating biochar-mediated suppression of phytophthora blight to develop products that can reliably suppress soil-borne diseases in the field.
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Potter, J. W., and A. W. McKeown. "Nematode biodiversity in Canadian agricultural soils." Canadian Journal of Soil Science 83, Special Issue (August 1, 2003): 289–302. http://dx.doi.org/10.4141/s01-064.
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The biodiversity of soil-inhabiting nematodes in Canada is incompletely known, as large areas of Canada’s landmass have not been surveyed for nematode fauna. Nematodes considered as indigenous are generally well adapted to a variety of ecological niches and climatic zones. Much of the available information is based on agricultural ecosystems and agricultural species, and thus is biased toward conditions in disturbed ecosystems and away from “primeval” ecology. Introduced nematode species are frequently quite pathogenic, even to exotic host plants from the same geographic point of origin. Estimates of crop loss due to single species infestations of pathogenic nematodes and the costs of nematode control using chemicals are reasonably well known, averaging about 10% of crop value, but ranging to 100% depending on the situation; the cost of damage by multiple-species infestations is less defined. Nematode-suppressive mechanisms are understood in only a few plant species; sulfur appears to be important as a constituent of active compounds in suppressive plants of agricultural origin. Similarly, some native plants are equally adapted with allelopathic chemicals that suppress nematodes. Management of nematode populations in agricultural soils by integrated crop management methods is at an early stage, requiring research to quantify effects of nematode-suppressive plants and soil amendments containing nitrogen. An integrated program could include nematode-suppressive plants, appropriate soil amendments, and the promotion of microbial antagonists. Different mathematical methods may be required to analyze and explain multi-factor nematode control systems. Less-toxic management systems could benefit the soil-inhabiting nematodes that predate arthropod soil pests. Further research on soil-borne nematodes may demonstrate the value of nematodes as indicators of agroecosystem health and environmental pollutants. Key words: Biocontrol, biodiversity, nematode distribution, nematode management, soil ecology
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Devi, Yumnam Bijilaxmi, and Thounaojam Thomas Meetei. "A Review: Suppressive Soils and its Importance." International Journal of Current Research in Biosciences and Plant Biology 5, no. 2 (February 6, 2018): 67–75. http://dx.doi.org/10.20546/ijcrbp.2018.502.007.
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Pyrowolakis, Aris, Andreas Westphal, Richard A. Sikora, and J. Ole Becker. "Identification of root-knot nematode suppressive soils." Applied Soil Ecology 19, no. 1 (January 2002): 51–56. http://dx.doi.org/10.1016/s0929-1393(01)00170-6.
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Michel, Vincent V., and T. W. Mew. "Effect of a Soil Amendment on the Survival of Ralstonia solanacearum in Different Soils." Phytopathology® 88, no. 4 (April 1998): 300–305. http://dx.doi.org/10.1094/phyto.1998.88.4.300.
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The effect of a soil amendment (SA) composed of urea (200 kg of N per ha) and CaO (5,000 kg/ha) on the survival of Ralstonia solanacearum in four Philippine soils was investigated in a series of laboratory experiments. Within 3 weeks after application, the SA either caused an initial decrease, a final decline, or no change in the pathogen population, depending on the particular soil type. An initial decrease occurred in a soil with a basic pH and resulted in a significantly (P < 0.001) lower pathogen population immediately and at 1 week after amending the soil. This decrease was probably due to the high pH in the soil during urea hydrolysis. A final decline in the R. solanacearum population after 3 weeks occurred in two soils in which nitrite accumulated after 1 week. In these soils, no decline in bacterial levels occurred when nitrite formation was inhibited by 2-chloro-6-trichloromethylpyridine. In the soil with low pH, no nitrite accumulated and the R. solanacearum population did not decline. The suppressive effects of pH and nitrite on R. solanacearum growth were confirmed by in vitro experiments. Ammonium reduced the growth of R. solanacearum, but was not suppressive. Interactions of pH with ammonium and nitrite also occurred, whereby ammonium reduced growth of R. solanacearum only at pH 9 and nitrite was suppressive only at pH 5. Nitrate had no effect on R. solanacearum growth in vitro.
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Durán, Paola, Gonzalo Tortella, Michael J. Sadowsky, Sharon Viscardi, Patricio Javier Barra, and Maria de la Luz Mora. "Engineering Multigenerational Host-Modulated Microbiota against Soilborne Pathogens in Response to Global Climate Change." Biology 10, no. 9 (September 3, 2021): 865. http://dx.doi.org/10.3390/biology10090865.
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Crop migration caused by climatic events has favored the emergence of new soilborne diseases, resulting in the colonization of new niches (emerging infectious diseases, EIDs). Soilborne pathogens are extremely persistent in the environment. This is in large part due to their ability to reside in the soil for a long time, even without a host plant, using survival several strategies. In this regard, disease-suppressive soils, characterized by a low disease incidence due to the presence of antagonist microorganisms, can be an excellent opportunity for the study mechanisms of soil-induced immunity, which can be applied in the development of a new generation of bioinoculants. Therefore, here we review the main effects of climate change on crops and pathogens, as well as the potential use of soil-suppressive microbiota as a natural source of biocontrol agents. Based on results of previous studies, we also propose a strategy for the optimization of microbiota assemblages, selected using a host-mediated approach. This process involves an increase in and prevalence of specific taxa during the transition from a conducive to a suppressive soil. This strategy could be used as a model to engineer microbiota assemblages for pathogen suppression, as well as for the reduction of abiotic stresses created due to global climate change.
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De Corato, Ugo. "Retraction: De Corato, U. Soil Microbiome Manipulation Gives New Insights in Plant Disease-Suppressive Soils from the Perspective of a Circular Economy: A Critical Review. Sustainability 2021, 13, 10." Sustainability 13, no. 4 (February 4, 2021): 1688. http://dx.doi.org/10.3390/su13041688.
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The journal retracts the article “Soil Microbiome Manipulation Gives New Insights in Plant Disease-Suppressive Soils from the Perspective of a Circular Economy: A Critical Review” by Ugo De Corato [...]
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Reeleder, R. D. "Fungal plant pathogens and soil biodiversity." Canadian Journal of Soil Science 83, Special Issue (August 1, 2003): 331–36. http://dx.doi.org/10.4141/s01-068.
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The role of biodiversity as it affects the control of soil-borne fungal pathogens is discussed. Soil-borne fungal plant pathogens have often proven difficult to manage with conventional methods of disease control. Nonetheless, researchers have characterized several naturally occurring “disease-suppressive” soils where crop loss from disease is less than would otherwise be expected. Suppressive soils can also result from the incorporation of various amendments into soil. In most cases, disease control in such soils has been shown to be biological in nature; that is, soil organisms appear to directly or indirectly inhibit the development of disease. Increased knowledge of the identity and functioning of these organisms may support the development of techniques that can be used to develop suppressiveness in soils that are otherwise disease-conducive. Populations of pathogens themselves have been shown to exhibit considerable genetic diversity; the ability of populations to respond to disease control measures should be considered when developing a management strategy. New molecular techniques can be exploited to better characterize soil communities, including the pathogens themselves, as well as community responses to various disease control options. The contributions of Canadian researchers to these areas are discussed and models for further study are proposed. Key words: Biocontrol, molecular technologies, functional diversity, integrated pest management
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Westphal, A., and J. O. Becker. "Transfer of Biological Soil Suppressiveness Against Heterodera schachtii." Phytopathology® 90, no. 4 (April 2000): 401–6. http://dx.doi.org/10.1094/phyto.2000.90.4.401.
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Heterodera schachtii-suppressive soil at a rate of either 1 or 10% (dry wt/wt) transferred suppressiveness against the beet cyst nematode to fumigated field plots when mixed into the upper 10-cm soil layer. Soil suppressiveness was established after 1 month of moist fallow and 77 days of Swiss chard cropping in the 10% transfer treatment and after 230 days in the 1% transfer treatment. The number of infective second-stage juveniles (J2) of H. schachtii, monitored initially at 150 degree-day intervals and later at 300 degree-day intervals, indicated the status of suppressiveness in the different treatments during the cropping period. In a greenhouse experiment, amending fumigated field soil with 0.1, 1.0, or 10% suppressive soil, suppressed multiplication of H. schachtii when soils were infested with an additional 5,000 J2. In a second greenhouse experiment, a fumigated sandy loam amended with 10 or 25% suppressive soil and a fumigated loam amended with 25% suppressive soil had significantly fewer eggs per cyst than the nonamended fumigated treatments when 1,000 J2 were added.
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Becker, Donna M., Linda L. Kinkel, and Janet L. Schottel. "Evidence for interspecies communication and its potential role in pathogen suppression in a naturally occurring disease suppressive soil." Canadian Journal of Microbiology 43, no. 10 (October 1, 1997): 985–90. http://dx.doi.org/10.1139/m97-142.
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Streptomyces strains isolated from potato scab suppressive (n = 9) and conducive (n = 5) soils were screened for their ability to produce diffusible chemicals that trigger antibiotic production in the pathogen-suppressive Streptomyces diastatochromogenes PonSSII. Using an Agrobacterium detection system, the strains were tested for the ability to produce homoserine lactone autoinducers. In addition, suppressive strain PonSSII was screened for production of an autoinducer for antibiotic production in a chemically defined liquid medium. Interspecies communication was investigated by growing suppressive and pathogenic strains individually in liquid medium and determining whether broth from these strains could induce antibiotic production in PonSSII. No evidence was found for production of homoserine lactones by any of the Streptomyces strains nor for the production of autoinducers by PonSSII. However, addition of conditioned broth from Streptomyces strains to cultures of PonSSII stimulated, suppressed, or had no effect on antibiotic production. Conditioned broth from suppressive strain 23 and pathogenic strain RB4 triggered antibiotic production by PonSSII at earlier times during culture growth and also enhanced antibiotic production levels compared with the control. The results suggest that interspecies communication between these Streptomyces species is occurring and may contribute to pathogen inhibition in the naturally occurring disease suppressive soil.Key words: Streptomyces, suppressive soil, interspecies communication, potato scab, autoinducers.
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Kinkel, Linda L., Matthew G. Bakker, and Daniel C. Schlatter. "A Coevolutionary Framework for Managing Disease-Suppressive Soils." Annual Review of Phytopathology 49, no. 1 (September 8, 2011): 47–67. http://dx.doi.org/10.1146/annurev-phyto-072910-095232.
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Döring, Thomas F., Dagmar Rosslenbroich, Christian Giese, Miriam Athmann, Christine Watson, Imre Vágó, János Kátai, Magdolna Tállai, and Christian Bruns. "Disease suppressive soils vary in resilience to stress." Applied Soil Ecology 149 (May 2020): 103482. http://dx.doi.org/10.1016/j.apsoil.2019.103482.
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Marban-Mendoza, Nahum, Roberto Garcia-E., M. Bess Dicklow, and Bert M. Zuckerman. "Studies onPaecilomyces marquandii from nematode suppressive chinampa soils." Journal of Chemical Ecology 18, no. 5 (May 1992): 775–83. http://dx.doi.org/10.1007/bf00994614.
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CHUANG, Tsai-young, and Wen-hsiung Ko. "Rhizoctonia solani-suppressive soils: Detection by chlamydospore germination." Japanese Journal of Phytopathology 54, no. 2 (1988): 158–63. http://dx.doi.org/10.3186/jjphytopath.54.158.
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Défago, G. "Microbial characteristics of disease-suppressive soils: a review." Experientia 42, no. 1 (January 1986): 94–95. http://dx.doi.org/10.1007/bf01975942.
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Li, Xiaoping, Ping Kong, Margery Daughtrey, Kathleen Kosta, Scott Schirmer, Matthew Howle, Michael Likins, and Chuanxue Hong. "Characterization of the Soil Bacterial Community from Selected Boxwood Gardens across the United States." Microorganisms 10, no. 8 (July 26, 2022): 1514. http://dx.doi.org/10.3390/microorganisms10081514.
Full textAbstract:
In a recent study, we observed a rapid decline of the boxwood blight pathogen Calonectria pseudonaviculata (Cps) soil population in all surveyed gardens across the United States, and we speculated that these garden soils might be suppressive to Cps. This study aimed to characterize the soil bacterial community in these boxwood gardens. Soil samples were taken from one garden in California, Illinois, South Carolina, and Virginia and two in New York in early summer and late fall of 2017 and 2018. Soil DNA was extracted and its 16S rRNA amplicons were sequenced using the Nanopore MinION® platform. These garden soils were consistently dominated by Rhizobiales and Burkholderiales, regardless of garden location and sampling time. These two orders contain many species or strains capable of pathogen suppression and plant fitness improvement. Overall, 66 bacterial taxa were identified in this study that are known to have strains with biological control activity (BCA) against plant pathogens. Among the most abundant were Pseudomonas spp. and Bacillus spp., which may have contributed to the Cps decline in these garden soils. This study highlights the importance of soil microorganisms in plant health and provides a new perspective on garden disease management using the soil microbiome.
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Fichtner, E. J., S. C. Lynch, and D. M. Rizzo. "Survival, Dispersal, and Potential Soil-Mediated Suppression of Phytophthora ramorum in a California Redwood-Tanoak Forest." Phytopathology® 99, no. 5 (May 2009): 608–19. http://dx.doi.org/10.1094/phyto-99-5-0608.
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Because the role of soil inoculum of Phytophthora ramorum in the sudden oak death disease cycle is not well understood, this work addresses survival, chlamydospore production, pathogen suppression, and splash dispersal of the pathogen in infested forest soils. Colonized rhododendron and bay laurel leaf disks were placed in mesh sachets before transfer to the field in January 2005 and 2006. Sachets were placed under tanoak, bay laurel, and redwood at three vertical locations: leaf litter surface, litter–soil interface, and below the soil surface. Sachets were retrieved after 4, 8, 20, and 49 weeks. Pathogen survival was higher in rhododendron leaf tissue than in bay tissue, with >80% survival observed in rhododendron tissue after 49 weeks in the field. Chlamydospore production was determined by clearing infected tissue in KOH. Moist redwood-associated soils suppressed chlamydospore production. Rain events splashed inoculum as high as 30 cm from the soil surface, inciting aerial infection of bay laurel and tanoak. Leaf litter may provide an incomplete barrier to splash dispersal. This 2-year study illustrates annual P. ramorum survival in soil and the suppressive nature of redwood-associated soils to chlamydospore production. Infested soil may serve as primary inoculum for foliar infections by splash dispersal during rain events.