Letteratura scientifica selezionata sul tema "Pratylenchus"

The population densities of four species of root-lesion nematodes (Pratylenchus) were examined in two cultivars of oat (Avena sativa L.) grown in greenhouse pots. The cultivar Saia harbored fewer P. neglectus and P. penetrans than the cultivar OAC Woodstock, while both cultivars were similar hosts for P. sensillatus. Pratylenchus crenatus did not develop in either cultivar.Key words: Oat, population density, Pratylenchus crenatus, Pratylenchus neglectus, Pratylenchus penetrans, Pratylenchus sensillatus

Thirteen species of Pratylenchidae: Pratylenchus coffeae, P. delattrei, P. loosi, P. neglectus, P. penetrans, P. pseudopratensis, P. thornei, P. vulnus, Pratylenchus sp., Pratylenchoides alkani, P. ritteri, Hirschmanniella sp. and Zygotylenchus guevarai were collected from different crops and plants throughout Iran. The specimens were identified using morphological and molecular methods. Morphometrics and morphology are given for Pratylenchus sp., P. delattrei, Pratylenchoides alkani and Hirschmanniella sp. The D2-D3 expansion segments of the 28S rRNA gene were amplified and sequenced for all 13 species studied. Diagnostic PCR-ITS-RFLP profiles are given for Pratylenchus delattrei, P. penetrans, P. pseudopratensis, Pratylenchus sp., Pratylenchoides alkani and P. ritteri. Pratylenchus neglectus and P. thornei, collected from cereal fields, P. loosi from tea plantations, P. coffeae from banana, P. penetrans from ornamental plants, P. vulnus from pines and Z. guevarai from almonds showed a high level of similarity in the D2-D3 sequences with corresponding GenBank sequences. Nucleotide differences between Iranian populations and reference species were in the intraspecific range. Pratylenchus delattrei, found in vegetable fields, and Pratylenchus sp. from palm rhizosphere, formed a highly supported clade with P. zeae, the two former species being morphologically very close to the latter except in tail shape. Pratylenchus pseudopratensis, from cereal fields, clustered with P. vulnus with low support. Phylogenetic relationships within Pratylenchus species were mainly congruent with those obtained in previous studies. Despite the morphological similarities between P. ritteri and P. alkani, the D2-D3 of 28S rRNA gene sequences differed by 5 bp. Hirschmanniella sp., from a rice field, formed a clade with H. loofi and H. kwazuna.

Root-lesion nematode species rank third only to root-knot and cyst nematodes as having the greatest economic impact on crops worldwide. A survey of plant-parasitic nematodes associated with decaying raspberries (Rubus sp.) in northern Italy revealed that root-lesion nematodes were the most frequently occurring species among other phytonematodes. Several Pratylenchus species have been associated with Rubus sp. in Canada (Quebec, British Columbia) and USA (North Carolina, Maryland, New Jersey) including P. penetrans and P. crenatus. In the roots and rhizosphere of symptomatic raspberries, nematodes of two Pratylenchus spp. were detected. Detailed morphometrics of the two root-lesion nematode isolates were consistent with Pratylenchus crenatus and with an undescribed Pratylenchus species. The extracted nematodes were observed and measured as live and fixed materials and subsequently identified by integrative taxonomy (morphometrically and molecularly). The latter species is described herein as Pratylenchus vovlasi sp. nov., resulting morphometrically closest to P. mediterraneus and phylogenetically to P. pratensis. The molecular identification of Pratylenchus vovlasi sp. nov. was carried out by sequencing the ITS region, D2-D3 expansion domains of the 28S rRNA gene and a partial region of the nuclear hsp90 gene. ITS-RFLP and sequence analyses revealed that Pratylenchus vovlasi sp. nov. had species-specific restriction profiles with no corresponding sequences present in the database. The phylogenetic relationships with ITS and D2-D3 sequences placed the Pratylenchus vovlasi sp. nov. in a clade with P. pratensis and P. pseudopratensis. This research confirms the occurrence of cryptic biodiversity within the genus Pratylenchus as well as the need for an integrative approach to the identification of Pratylenchus species.

Root-lesion nematodes (Pratylenchus spp.) of the genus Pratylenchus Filipjev, 1936, are among the most important nematode pests on soybean (Glycine max (L.) Merr.), along with soybean cyst and root-knot nematodes. In May 2015 and 2016, a total of six soil samples were collected from a soybean field in Walcott, Richland County, ND and submitted to the Mycology and Nematology Genetic Diversity and Biology Laboratory (MNGDBL), USDA, ARS, MD for analysis. Later, in 2019, additional nematodes recovered from a greenhouse culture on soybean originally from the same field were submitted for further analysis. Males, females, and juveniles of Pratylenchus sp. were recovered from soil and root samples and were examined morphologically and molecularly. DNA from single nematodes were extracted, and the nucleotides feature of three genomic regions targeting on the D2–D3 region of 28S rDNA and ITS rDNA and mitochondrial cytochrome oxidase subunit I (COX1) gene were characterized. Phylogeny trees were constructed to ascertain the relationships with other Pratylenchus spp., and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to provide a rapid and reliable differentiation from other common Pratylenchus spp. Molecular features indicated that it is a new, unnamed Pratylenchus sp. that is different from morphologically closely related Pratylenchus spp., including P. convallariae, P. pratensis, P. fallax, and P. flakkensis. In conclusion, both morphological and molecular observations indicate that the North Dakota isolate on soybean represents a new root-lesion nematode species which is named and described herein as Pratylenchus dakotaensis n. sp.

AbstractThe distribution and diversity of Pratylenchus species associated with Ammophila arenaria was investigated in its natural range of distribution. Twelve localities with vigorous stands of A. arenaria along the European Atlantic and Mediterranean coasts were sampled. The populations were identified based on morphology and morphometrics, and further characterised based on sequences of the rDNA D2D3 region. Pratylenchus spp. were present in all of the sampled sites. A total of 19 populations were detected belonging to Pratylenchus dunensis, P. brzeskii, P. pratensis or P. penetrans. Pratylenchus dunensis was widely distributed from Blakeney Point (UK) to Comporta (Portugal). Pratylenchus brzeskii was found in South European localities along the Atlantic coast and also in the Mediterranean region. Pratylenchus pratensis was found associated with A. arenaria for the first time and occurred at different locations along the Atlantic coast. Pratylenchus penetrans was only detected in Biarritz (France). The P. dunensis populations from the south west Iberian Peninsula differed from the original P. dunensis description and showed two incisures on the lip region instead of one. Pratylenchus brzeskii populations did not vary morphologically from the original descriptions; however, the range of their morphometrical characters was wider than that of the type population. The D2D3 rDNA region revealed large interspecific and low intraspecific variation, supporting the morphological identification. The phylogenetic relationships of the populations with respect to other species of the genus were inferred from partial sequences of the rDNA and positioned P. dunensis within the same group as P. convallariae, P. penetrans and P. fallax.

Tabular (multientry) key to Pratylenchus is presented, and functioning of the computerized multientry image-operating key developed on the basis of the stepwise computer diagnostic system BIKEY-PICKEY is described. Monoentry key to Pratylenchus is given, and diagnostic relationships are analysed with the routine taxonomic methods as well as with the use of BIKEY diagnostic system and by the cluster tree analysis using STATISTICA program package. The synonymy Pratylenchus scribneri Steiner in Sherbakoff & Stanley, 1943 = P. jordanensis Hashim, 1983, syn. n. is established. Conclusion on the transition from amphimixis to parthenogenesis as one of the leading evolutionary factors for Pratylenchus is drawn.

Due to Israel’s successful agricultural production and diverse climatic conditions, plant-parasitic nematodes are flourishing. The occurrence of new, previously unidentified species in Israel or of suggested new species worldwide is a consequence of the continuous withdrawal of efficient nematicides. Among plant-parasitic nematodes, migratory endoparasitic species of the genus Pratylenchus are widely distributed in vegetable and crop fields in Israel and are associated with major reductions in quality and yield. This review focuses on the occurrence, distribution, diagnosis, pathogenicity, and phylogeny of all Pratylenchus species recorded over the last few decades on different crops grown throughout Israel—covering early information from nematologists to recent reports involving the use of molecular phylogenetic methodologies. We explore the accepted distinction between Pratylenchus thornei and Pratylenchus mediterraneus isolated from Israel’s northern Negev region, and address the confusion concerning the findings related to these Pratylenchus species. Our recent sampling from the northern Negev revealed the occurrence of both P. thornei and P. mediterraneus on the basis of molecular identification, indicating P. mediterraneus as a sister species of P. thornei and their potential occurrence in a mixed infection. Finally, the efficiencies of common control measures taken to reduce Pratylenchus’ devastating damage in protected crops and field crops is discussed.

To investigate nematicidal activity against the root-lesion nematode, Pratylenchus coffeae, the methanolic extracts were obtained from 5 medicinal plants in Vietnam. Methanol extracts of the 5 samples were screened for nematicidal activity against Pratylenchus coffeae in vitro. Of the plant extracts tested, a 5 mg/ml concentration of Terminalia nigrovenulosa extract showed the highest level (95.0%) of nematicidal activity against Pratylenchus coffeae at 9 h after treatment. The remainder of the plant extracts was followed by Cinnamomum camphora (66.7%), Jasminum suptriplinerve (30.8%), Premna integrifolia (6.7%), and Treptocaulon juventas (5.8%). A 2.0 mg/mlconcentration of T. nigrovenulosa resulted in 13.3, 42.5, 62.5 and 86.7% at 1, 3, 5 and 7 h after treatment, respectively against Pratylenchus coffeae. Concentration of 0.1, 0.5, 1.0 and 2.0 mg/ml of T. nigrovenulosa resulted in 26.7, 71.7, 78.3 and 86.7% effectiveness respectively, at 7 h after treatment. Also, at 3 days after exposure to T. nigrovenulosa, hatch was inhibited by 60.0, 45.8, 17.5 and 5.8% at 0.1, 0.5, 1.0 and 2.0 mg/ml, respectively. Hatch was inhibited by 65.0, 50.8, 21.7 and 6.7% at 0.1, 0.5, 1.0 and 2.0 mg/ml respectively, at 6 days after exposure to T. nigrovenulosa. The mortality rate and hatch inhibition increased with increasing incubation time for crude extract of T. nigrovenulosa. Trong nghiên cứu này, 5 cây thuốc (Cinnamomum camphora, Jasminum suptriplinerve, Premna integrifolia, Terminalia nigrovenulosa, Treptocaulon juventas) đã được sử dụng làm nguyên liệu chiết xuất bằng methanol để thử hoạt tính kháng tuyến trùng Pratylenchus coffeae. Kết quả cho thấy chiết xuất từ cây Terminalia nigrovenulosa biểu hiện hoạt tính kháng tuyến trùng cao nhất (95,0%) sau 9 giờ xử lý với nồng độ 5 mg/ml. Hoạt tính kháng tuyến trùng của các chất chiết xuất được biểu hiện theo thứ tự giảm dần lần lượt là C. camphora (66,7%), J. suptriplinerve (30,8%), P. integrifolia (6,7%) và T. juventas (5,8%). Với nồng độ 2 mg/ml của chất chiết xuất từ T. nigrovenulossa biểu hiện hoạt tính gây chết tuyến trùng Pratylenchuss coffeae là 13,3; 42,5; 62,5 và 86,7% sau 1, 3, 5 và 7 giờ xử lý theo thứ tự. Ở cùng thời điểm sau xử lý 7 giờ, các nồng độ 0,1; 0,5; 1,0 và 2,0 mg/ml chiết xuất của T. nigrovenulossa có hoạt tính gây chết tuyến trùng Pratylenchus coffeae lần lượt là 26,7; 71,7; 78,3 và 86,7%. Bên cạnh đó, chất chiết xuất của T. nigrovenulossa cũng cho thấy tỷ lệ ức chế trứng nở cao. Cụ thể là sau 3 ngày xử lý với chất chiết xuất của T. nigrovenulossa, tỷ lệ ức chế trứng không nở là 60,0; 45,8; 17,5 và 5,8% at 0,1; 0,5; 1,0 và 2,0 mg/ml theo thứ tự. Sau 6 ngày xử lý với chất chiết xuất của T. nigrovenulossa, tỷ lệ ức chế trứng nở là 65,0; 50,8; 21,7 và 6,7% tại nồng độ 0,1; 0,5; 1,0 và 2,0 mg/ml theo thứ tự. Tỷ lệ gây chết và tỷ lệ ức chế của chất chiết xuất phụ thuộc vào cả thời gian và nồng độ xử lý.

The Pasteuria genus comprises gram-positive bacteria that are obligate parasites of arthropods and nematodes. Species of this genus are ubiquitous, being present in both aquatic and terrestrial environments all around the world. Pasteuria was first described as a genus at the end of the 19th century and has undergone considerable reclassification regarding its member species. Starting in the 1980s, a more meticulous classification effort regarding the identification of Pasteuria spp., and its parasitic habits began. These studies were strongly motivated by the ability of individuals of this genus to parasitize phytopathogenic nematodes of several plant species. Each species of the genus Pasteuria establishes a strict parasitic relationship with a specific genus of phytonematode. As an example of this interaction, Pasteuria thornei is a parasite restricted to the genus Pratylenchus, which comprises the nematodes popularly known as root-lesion-nematodes, a pest of several agronomically important crops. Considering the current relevance of studies involving the biological control of phytonematodes, in the present work three experiments were carried out, each one containing a replicate, totaling, therefore, six experiments. Two experiments were intended to verify the efficacy of P. thornei as a biological control agent (BCA) of Pratylenchus brachyurus in soybean. The remaining four experiments had a similar objective in the scope of the Pratylenchus zeae - maize pathosystem. Two experiments were carried out to verify the efficacy of P. thornei as a biological control agent for P. zeae in maize, and afterwards, two additional experiments were performed in order to verify the capacity of the BCA to reduce productivity losses in corn plants due to the parasitism of this nematode. For the soybean experiments, the following treatments were added to the seeds of the cultivar SYN1080: three different concentrations of P. thornei endospores per seed (5x106, 107 e 1,5x107), a commercial control group for comparison containing abamectin (0.58mg/seed) and a mixed treatment containing abamectin (0.58 mg / seed) and 107 P. thornei endospores. Untreated seeds were used as a control group. The treatments were sown in 500 cm3 plastic cups containing soil inoculated with 1000 nematodes (experiment 1) and 600 nematodes (experiment 2). Fresh root mass and nematodes extracted from the roots of each plant were used as parameters of evaluation, taking place 60 and 90 days after inoculation (DAI). Only the treatment with the highest concentration of P. thornei (1.5x107) reduced the final population of nematodes significantly, reaching 30-50% of reduction compared to the untreated seeds. However, treatments containing the commercial control abamectin were superior in reducing the final population of nematodes in all experiments evaluated. Regarding the maize efficacy experiments, CELERON hybrid seeds were treated as described: four concentrations of P. thornei endospores per seed (5x106, 107, 1,5x107, 2x107), a commercial control group for comparison containing abamectin (0.58 mg / seed) and a mixed treatment containing abamectin (0.58 mg / seed) and 107 P. thornei endospores. Untreated seeds were used as a control group. The treated maize seeds were planted in 500 cm3 plastic cups containing soil inoculated with 4000 and 1000 individuals for the efficacy experiments 1 and 2, respectively. Evaluations occurred at 60 and 90 DAI. For the productivity assays, the experiments 3 and 4 were carried out under a screened greenhouse, with experimental plots consisting of 9L pots filled with artificially infested soil. Seeds of the CELERON hybrid received the following treatments: abamectin (0.58mg / seed), P. thornei (107 endospores / seed) and mixed treatment containing both abamectin (0.58mg / seed) and P. thornei (107 endospores / seed). Two additional treatments containing untreated seeds served as controls, with and without the presence of Pratylenchus zeae. The evaluation measured several agronomic traits, such as dry weight of the aerial parts, fresh mass of roots at harvest and total weight of grains. In addition, the nematode population was measured in fresh roots at 45, 90 days and at the time of harvest. Efficacy trials showed that the highest concentrations of P. thornei (1.5x107 and 2x107) have a considerable potential of P. zeae control. The nematode population reduction was 54 and 47% in experiments 1 and 2, respectively, for the highest P. thornei concentration treatment. The commercial formulation containing abamectin showed a reduction of P. zeae population above 90% in both experiments. Regarding the maize productivity experiments, control potential of nematodes by P. thornei was similar to that observed in the efficacy study. The treatments containing abamectin had an effect on the mitigation of yield losses caused by P. zeae in both experiments. The mixed treatment (abamectin and P. thornei) and the one containing exclusively P. thornei presented a positive performance in both replicates. In none of the experiments synergistic or additive effects were observed between P. thornei and abamectin. With the data obtained in these experiments, the control potential of P. thornei on P. brachyurus and P. zeae in soybean and corn, respectively, is evident. Additionally, P. thornei and abamectin in the form of seed treatment, show potential in mitigating yield losses caused by P. zeae in maize. This highlights the importance of P. thornei as an additional tool for the management of root lesion nematodes in soybean and maize, and should encourage subsequent work.
O gênero Pasteuria compreende bactérias gram-positivas parasitas obrigatórias de artrópodes e nematoides. A distribuição das espécies deste gênero pelo mundo é ubíqua, podendo ser encontradas em ambientes aquáticos e terrestres. Este gênero foi descrito no final do século XIX e sofreu consideráveis reclassificações em relação às espécies nele compreendidos. A partir da década de 80, deu-se início a um esforço de classificação mais minucioso com relação à identificação de Pasteuria spp. e seus hábitos parasitários. Estes estudos foram motivados, principalmente, pela capacidade dos indivíduos deste gênero em parasitar nematoides fitoparasitas de diversas culturas. Cada espécie do gênero Pasteuria estabelece relações parasitárias com um gênero específico de fitonematoide. A exemplo desta interação, Pasteuria thornei é um parasita restrito ao gênero Pratylenchus, que compreende os nematoides causadores das lesões radiculares, daninhos a diversas culturas de importância agronômica. Considerando a relevância atual de estudos envolvendo o controle biológico de fitonematoides, no presente trabalho foram realizados três experimentos, cada um contendo uma réplica em época distinta, totalizando, portanto, seis experimentos. Dois experimentos tiveram por objetivo verificar a eficácia de P. thornei como agente de controle biológico (ACB) de Pratylenchus brachyurus na cultura da soja. E os demais quatro experimentos abordaram o patossistema Pratylenchus zeae-milho. Para esse objetivo, foram realizados dois experimentos com o intuito de verificar a eficácia de P. thornei como agente de controle biológico de P. zeae em milho, e outros dois experimentos para testar a capacidade do ACB em reduzir a perda de produtividade em plantas de milho decorrente do parasitismo do nematoide. Para os experimentos de soja, às sementes da cultivar SYN1080 foram adicionados os tratamentos como se segue: três concentrações de endósporos de P. thornei por semente (5x106, 107 e 1,5x107), um grupo de controle químico comercial para comparação contendo abamectina (0,58 mg / semente) e um tratamento misto contendo abamectina (0,58 mg / semente) e 107 endósporos de P. thornei. Sementes não tratadas foram utilizadas como testemunha. As sementes tratadas foram semeadas em copos de plástico de 500 cm3 contendo solo inoculado com 1000 nematoides (experimento 1) e 600 nematoides (experimento 2). A massa de raiz fresca e os nematoides extraídos das raízes de cada planta foram utilizados como critério de avaliação dos experimentos, a qual foi realizada aos 60 e 90 dias após a inoculação (DAI). Apenas o tratamento com a maior concentração de P. thornei (1,5x107) reduziu a população final de nematoides de maneira significativa atingindo 30-50% de redução, comparado àquele contendo sementes não tratadas. No entanto, os tratamentos que contém abamectina foram superiores na redução da população final de nematoides em todos os experimentos avaliados. Em relação aos experimentos de eficácia em milho, sementes do híbrido CELERON foram tratadas como explicitado: quatro concentrações de endósporos de P. thornei por semente (5x106, 107, 1,5x107 e 2x107), um grupo de controle comercial para comparação contendo abamectina (0,58 mg / semente) e um tratamento misto contendo abamectina (0,58 mg / semente) e 107 endósporos de P. thornei. As sementes tratadas de milho foram semeadas em copos de plástico de 500cm3 contendo solo inoculado com 4000 e 1000 indivíduos para os experimentos de eficácia 1 e 2, respectivamente. As avaliações ocorreram aos 60 e 90 DAI. Para os estudos de produtividade, foram realizados os experimentos 3 e 4 sob um telado com parcelas experimentais constituídas por vasos de 9L preenchidos de solo infestado artificialmente. Sementes do híbrido CELERON foram utilizadas contendo os seguintes tratamentos: abamectina (0,58mg / semente), P. thornei (107 endósporos/semente) e um tratamento misto contendo abamectina (0,58mg / semente) e P. thornei (107 endósporos/semente). Dois tratamentos adicionais contendo sementes não tratadas serviram de testemunhas, com e sem Pratylenchus zeae. A avaliação consistiu na medição de várias características agronômicas, como peso seco da parte aérea, massa fresca de raízes no momento da colheita e peso total dos grãos. Adicionalmente, foi mensurada a população de nematoides em raízes frescas aos 45, 90 dias e no momento da colheita. Os ensaios de eficácia mostraram que as concentrações mais elevadas de P. thornei (1,5x107 e 2x107) possuem um potencial mensurável de controle de P. zeae. A redução da população de nematoides foi de 54 e 47% nos experimentos 1 e 2, respectivamente. A formulação comercial de abamectina mostrou uma redução da população de nematoides superior a 90% em ambos os experimentos. No que diz respeito aos experimentos de produtividade de milho, o potencial de controle de nematoides por P. thornei foi semelhante ao observado no estudo de eficácia. O tratamento com abamectina teve efeito na redução das perdas de rendimento causadas por P. zeae em ambos os experimentos; assim como os tratamentos misto (abamectina e P. thornei) e aquele contendo apenas P. thornei que apresentaram desempenho positivo em ambas as repetições. Em nenhum dos experimentos foi observado efeito sinérgico ou aditivo entre P. thornei e abamectina. Com os dados obtidos nestes experimentos, fica evidente o potencial de controle de P. thornei sobre P. brachyurus e P. zeae em soja e milho, respectivamente. Ainda, tanto P. thornei quanto abamectina apresentam o potencial de mitigar as perdas de rendimento causadas por P. zeae em milho através do tratamento de sementes. Isso evidencia a importância de P. thornei como uma ferramenta adicional para o manejo desses nematoides, e deve encorajar trabalhos subsequentes.

Os danos causados por Pratylenchus brachyurus e P. zeae às variedades de cana-de-açúcar SP70-1143 e SP71-1406 foram avaliados em dois ensaios em vasos de 150 litros. Cada ensaio constou da inoculação de 0, 200, 400 ou 800 nematóides por litro de solo de uma ou outra espécie de Pratylenchus. As populações de nematóides nas raízes e parâmetros de crescimento e produção foram avaliados ao longo do ciclo e por ocasião do corte, aos 17 meses. P. braghyurus se multiplicou nas raízes das duas variedades sem causar prejuízos a nenhuma delas, que foram consideradas tolerantes ao nematóide. Na variedade SP70-1143, P. zeae só se multiplicou nas plantas inoculadas com 200 nematóides por litro de solo, porém não causou reduções nos pesos frescos dos colmos e total da parte aérea, em relação às demais. SP71-1143 foi tida como resistente a P. zeae. Na variedade SP71-1406, as maiores populações de P. zeae foram registradas nas plantas que receberam 400 ou 800 nematóides por litro de solo. Estas plantas também mostraram reduções significativas nos pesos frescos dos colmos e total da parte aérea, em relação as demais. SP71-1406 foi considerada susceptível a P. zeae
Damage to two sugarcane varieties resulting from infestation by Pratylenchus brachyurus and P. zeae were evalueted in two experiments. Each experiment consisted of inoculation with 0, 200, 400 or 800 nematodes/l soil from one or another Pratylenchus species on the varieties SP70-1143 and SP71-1406, the most cultivated in São Paulo State, nowadays. Single buds from both varieties were grown in 150 l pots, containing sterilized sandy soil and were inoculated 30 days after planting. Nematode population in roots and parameters were evalueted along the plant growth cicle and at the harvest, 17 months after planting. P. brachyurus reproduction was observed at the roots of two varieties, but no growth reduction was caused by the parasities. Both varieties were considered tolerant to P. brachyurus. On SP70-1143, P. zeae reproduction ocurred only at initial population of 200 nematodes/l soil. At the harvest, these plants only showed significant decreases in fresh weight of top cane plus leaves and dry weight of roots when compared with the plants without nematodes. SP-1143 was classified as resistant to P. zeae. As far as SP71-1406 is concerned, the higher P. zeae populations were observed in the pots inoculated with 400 or 800 nematodes/l soil. In these cases, significant reduction on fresh weight of shoots and fresh weight of aerial parts observed. SP71-1406 was considered susceptible to P. zeae

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Soybean is the most important crop in Brazil, which is known for being the second largest producer of the grain. There are several phytosanitary problems that affect the culture and cause losses in production, including plant nematodes. Pratylenchus brachyurus is one of the most widespread nematodes in soybean producing areas of Brazil. The search for genotypes that have resistance to this plant nematode has been widespread, but there is still disagreement regarding the behavior of several brazilian cultivars. Evaluation of soybean cultivars in infested areas has not indicated the existence of materials resistant or tolerant. Thus, this study was to evaluate the reaction to P. brachyurus of six soybean cultivars and eight F1 populations originated from crosses in partial diallel arrangement. We also evaluate the behavior of cultivars exposed to different inoculum concentrations in three planting dates. The first study aimed to evaluate the reaction of cultivars and F1 populations of the plant nematode P. brachyurus. Experiment were conducted in naturally infested field conditions to evaluate the cultivars MT/BR51 (Xingu), BRSGO Caiapônia, MSOY 8360RR, BRS 8560RR, Emgopa 313RR and MSOY 7639RR and another in greenhouse conditions, which were evaluated in addition to these cultivars, the F1 progenies obtained by crossing between the parents of group I (Xingu and BRSGO Caiapônia) and group II (MSOY 8360RR, BRS 8560RR, Emgopa 313RR and MSOY 7639RR). In the field experiment all cultivars were susceptible to plant nematode, except the cultivar Xingu that showed behavior of resistance in the evaluation at 60 days after planting (DAP) with a RF of 0,80. However, this cultivar enabled the multiplication of P. brachyurus in the evaluation at 30 DAP. In the greenhouse condition, all parents behaved as resistant. The diallel analysis revealed the presence of non-additive and additive effects in controlling resistance. The Xingu cultivar showed the best GCA and cross between the cultivars Xingu and MSOY 8360 RR was the most promising in generating progeny with resistance reaction. The second study aimed to evaluate the reaction of soybean cultivars BRSGO Caiapônia, MT/BR51 (Xingu), MSOY 8360RR, MSOY 7639RR, BRS 8560RR and Emgopa 313RR, subjected to different inoculums concentrations in three planting dates. For this, three experiments were conducted under greenhouse conditions to evaluate the reaction of soybean cultivars under initial inoculum concentrations of 200, 400 or 600 juveniles and/or adults of P. brachyurus per plant in three planting dates. The planting date interferes with the infection of P. brachyurus and in the development of plants. Temperatures recorded in the second planting date, probably favored the multiplication of the nematode resulting in the lowest root development of cultivars. In this planting date was observed the highest population density of the nematode. In the third planting date the average temperature of the environment presented milder. At this planting date it was noted that all cultivars had lower population densities of P. brachyurus and resistant behavior (RF<1). There was a trend towards growing the plant nematode population density increased as the inoculums concentration in the first and second planting dates. In their results, we can observe the vulnerability of Brazilian soybean genotypes to P. brachyurus and the existence of variability of the pathogen. More research is needed to identify genotypes that have resistance to this nematode, as well as population studies related to the nematode. These studies should take into account the annual variation of nematode population due to low infectivity observed in dates of warmer temperatures.
A soja é a cultura agrícola mais importante do Brasil, o qual se destaca por ser o segundo maior produtor mundial do grão. Diversos são os problemas fitossanitários que afetam a cultura e ocasionam perdas na produção, dentre eles os fitonematoides. Pratylenchus brachyurus é um dos nematoides mais disseminados na cultura da soja nas áreas produtoras do Brasil. A busca por genótipos de soja que apresentem resistência a este fitonematoide tem sido muito difundida, porém, há ainda divergência em relação ao comportamento de diversas cultivares brasileiras. A avaliação de cultivares de soja em áreas infestadas não tem indicado a existência de materiais resistentes ou tolerantes. Dessa forma, neste estudo avaliou-se a reação ao P. brachyurus de seis cultivares de soja e de oito populações F1 originadas por cruzamentos em esquema de dialelos parciais. Avaliou-se também o comportamento dessas cultivares, submetidas a diferentes concentrações de inóculo, em três épocas de plantio. O primeiro estudo teve como objetivo avaliar a reação das cultivares e das populações F1 ao fitonematoide P. brachyurus. Para isso, foram conduzidos dois experimentos, um em condições de campo naturalmente infestado, avaliando-se as cultivares MT/BR51 (Xingu), BRSGO Caiapônia, MSOY 8360RR, BRS 8560RR, Emgopa 313RR e MSOY 7639RR, e outro em condições de casa de vegetação, em que foram avaliadas, em esquema de dialelo parcial, além destas cultivares, as progênies F1 obtidas pelo cruzamento entre os genitores do grupo I (Xingu e BRSGO Caiapônia) e do grupo II (MSOY 8360RR, BRS 8560RR, Emgopa 313RR e MSOY 7639RR). No experimento de campo todas as cultivares comportaram-se como suscetíveis, com exceção da cultivar Xingu que apresentou comportamento de resistência na avaliação aos 60 dias após a semeadura (DAS) com um FR de 0,80. Porém, na avaliação aos 30 DAS esta cultivar possibilitou a multiplicação de P. brachyurus. Já em casa de vegetação, todos os genitores comportaram-se como resistentes. A análise dialélica evidenciou a presença de efeitos aditivos e não aditivos no controle da resistência. A cultivar Xingu apresentou a melhor capacidade geral de combinação e o cruzamento entre as cultivares Xingu e MSOY 8360RR foi o mais promissor em gerar progênies com reação de resistência. O segundo estudo teve como objetivo avaliar o comportamento das cultivares BRSGO Caiapônia, MT/BR 51 (Xingu), MSOY 8360RR, MSOY 7639RR, BRSG 8560RR e Emgopa 313RR submetidas a diferentes concentrações de inóculo de P. brachyurus, em três épocas de plantio. Para isso, foram conduzidos três experimentos sob condições de casa de vegetação, para avaliar a reação das cultivares com relação às concentrações iniciais de inóculo de 200, 400 ou 600 juvenis e/ou adultos de P. brachyurus por parcela, semeadas em três épocas diferentes. A época de semeadura interferiu na infecção de P. brachyurus e, consequentemente, no desenvolvimento das plantas. As temperaturas registradas na segunda época de semeadura, provavelmente, favoreceram a multiplicação de P. brachyurus ocasionando o menor desenvolvimento das raízes das cultivares. Nesta época observou-se a maior densidade populacional de P. brachyurus. Na terceira época, a temperatura média do ambiente apresentou-se mais amena, quando se notou que todas as cultivares apresentaram baixas densidades populacionais de P. brachyurus e comportamento resistente. Observou-se tendência de aumento na densidade populacional do fitonematoide à medida que se aumentou a concentração de inóculo, nas primeira e 5 segunda épocas de plantio. Com base nesses resultados observa-se a vulnerabilidade dos genótipos brasileiros de soja ao P. brachyurus e a existência de variabilidade do patógeno. Mais pesquisas são necessárias visando à identificação de genótipos que possuam resistência a este nematoide, assim como estudos populacionais relacionados ao P. brachyurus. Nestes estudos deve-se levar em conta a variação anual da população do nematoide em razão da baixa infectividade observada em épocas de temperaturas mais amenas.

Para um manejo bem sucedido, devem-se integrar diversas estratégias de controle. A utilização de cultivares resistentes é a maneira mais eficiente, porém as informações quanto às formas de avaliar a reação de cultivares são escassas. Devido à importância de Pratylenchus brachyurus e a falta de padronização de metodologias para avaliação de ensaios em casa de vegetação, objetivou-se estudar metodologias para seleção de genótipos de soja quanto à reação a P. brachyurus baseadas em diferentes níveis de inóculo e épocas de avaliação, bem como a contribuição da utilização de uma escala de notas em função da percentagem de escurecimento das raízes nas avaliações. Foram conduzidos dois ensaios em casa de vegetação na estação da GDM GENÉTICA DO BRASIL LTDA, em Cambé – PR, em 2015. No primeiro ensaio verificou-se a reação de 45 genótipos de soja a P. brachyurus aos 45, 60 e 90 dias após a inoculação de 600 espécimes/planta. Para o segundo foram selecionados nove dos genótipos estudados anteriormente e acrescentado o genótipo 46, não utilizado no primeiro ensaio e avaliados aos 45 e 60 dias após a inoculação de 800 e 1000 espécimes/planta. O delineamento experimental de ambos foi o inteiramente casualizado, em esquema fatorial, com cinco repetições. As variáveis avaliadas foram: fator de reprodução (FR), número de nematoides por grama de raiz (nem/g raiz) e escala de notas para escurecimento de raízes. Os dados foram submetidos à análise de variância e as médias comparadas pelo teste de Scott-Knott a 5% de probabilidade. Os dois ensaios apresentaram interação significativa entre os fatores, apontando dependência entre genótipo, época de avaliação e nível de inóculo para as variáveis respostas. No primeiro ensaio, houve diferença significativa entre os genótipos para FR e nema/g raiz quando se avaliou aos 60 e 90 dias após a inoculação, mas não aos 45 dias. De modo geral, maiores valores de FR e nem/g raiz foram obtidos na avaliação mais tardia, o que não se repetiu para nota, que apresentou maiores médias aos 60 dias. No segundo ensaio, aos 45 dias de avaliação não houve diferença significativa entre os genótipos para as três variáveis avaliadas, nos dois níveis de inóculo utilizados. Por outro lado, aos 60 dias, para FR e nem/g raiz os genótipos diferiram entre si, apenas no nível de 800 espécimes/planta. No entanto, de acordo com as notas de escurecimento, nos dois níveis de inóculo estudados, os genótipos apresentaram diferença estatística entre si. No entanto, não houve diferença de escurecimento entre os níveis de inóculo utilizado. Portanto, nas condições deste trabalho, não recomenda-se a avaliação aos 45 dias após a inoculação dos nematoides; recomenda-se a inoculação de 800 indivíduos por planta com avaliação aos 60 dias; e a escala visual de notas pode ser uma ferramenta importante para auxiliar na seleção de genótipos para programas de melhoramento; porém são necessários mais estudos em nível de campo.
For a successful management should be integrated various control strategies. The use of resistant cultivars is the most efficient way, but the information about the reaction of cultivars are scarce. Due to the importance of Pratylenchus brachyurus and the lack of standardization of methodologies for assessment of testing in the greenhouse, aimed to study methods for selection of soybean genotypes for resistance to P. brachyurus based on different levels of inoculum and evaluation periods, as well as the contribution of the use of a visual rating scale according to the percentage of dark roots in the ratings. Two experiments were conducted in a greenhouse in the GDM GENETICS OF BRAZIL LTDA station in Cambé - PR in 2015. In the first study was checking the reaction of 45 soybean genotypes to P. brachyurus at 45, 60 and 90 days after inoculation of 600 specimens / plant. For the second nine genotypes were selected previously studied, added the genotype 46, not used in the first test and evaluated at 45 and 60 days after inoculation of 800 and 1000 specimens / plant. The experimental design of both was completely randomized in a factorial design with five replications. The variables evaluated were: reproduction rate (FR), number of nematodes per root gram (nema / g root) and degree of root darkening. Data were submitted to analysis of variance and means were compared by the Scott-Knott test at 5% probability. The two trials showed a significant interaction between the factors pointing dependence between genotype evaluation time and inoculum level for the response variables. In the first trial, there were significant differences among genotypes for FR and nema / g root when evaluated at 60 and 90 days after inoculation, but not 45 days. In general, higher FR values and or / g root were obtained in later evaluation, which was not repeated to note, that showed higher averages 60 days. In the second trial, the 45-day trial there was no significant difference between genotypes for the three variables evaluated in two inoculum levels used. Furthermore, at 60 days, and even for FR / g root genotypes differed only in the level of 800 specimens / plant. However, according to the blackout notes, the two inoculum levels studied, the genotypes showed statistical difference between them. However, no difference between the dimming levels of inoculum used. Therefore, in the conditions of this work, not recommended to the evaluation at 45 days after inoculation of nematodes; it is recommended to inoculate 800 specimens per plant and evaluation at 60 days; and the visual rating scale can be an important tool to assist in the selection of genotypes for breeding programs; but more studies are needed in the field level.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Phytonematodes can significantly limite the soybean yield. Due to inadequate soil management and the fact that there is not efficient nematicide in the market. The, P. brachyurus known as the nematode root lesions, has been spreading rapidly and increased its importance in the Brazil fields. The aim of this study was to evaluate the effect of organic fertilizers in soil and liquid form in control of the nematode in soybean roots, on Fepagro 36RR.The design was a randomized block design with six treatments and nine replicates. There treatments were evaluated with fertilizers in solid and liquid form: soil+ vermicompost manure (VERM), soil+ compost (manure and straw, COMP), soil +organic compound Ecocitrus (ECO) and two control without fertilization, with the presence or absence of the nematode. Samples were collected at 25, 50 and 75 days after inoculation of phytonematode, evaluating height, fresh shoot and root mass the juvenils number of P. brachyurus in the roots. The results show that after 50 days, the treatments applied in solid form were suppressive to control P. brachyurus and development of soybean plants. 75 days, it is observed that plants grown with VERM were less affected, with the number of nematodes penetrated 13% and 26% lower than that observed in the ECO and COMP fertilizer. New tests should be conducted using compost of cattle manure, vermicompost and commercial waste to confirm the potencial of organic fertilizer in control P. brachyurus in soybean field.
Os fitonematoides podem limitar significativamente a produtividade da soja. Devido ao manejo inadequado do solo e ao fato de não existir nematicidas químicos eficientes no mercado. O Pratylenchus brachyurus conhecido como nematoide das lesões radiculares, tem se disseminado rapidamente e aumentado sua importância nas lavouras do Brasil. O objetivo deste trabalho foi avaliar a ação de fertilizantes orgânicos na forma sólida e líquida no controle de P. brachyurus, em raízes de soja, cultivar Fepagro 36 RR. O delineamento utilizado foi de blocos ao acaso com seis tratamentos e três repetições. Foram três tratamentos avaliados com os fertilizantes na forma sólida e líquida: solo+vermicomposto de esterco bovino (VERM), solo+composto (esterco bovino e palha, COMP), solo+fertilizante orgânico Ecocitrus (Eco) e dois controles sem adubação, com a presença e ausência do P. brachyurus. As coletas foram realizadas aos 25, 50 e 75 dias após a inoculação do fitonematoide. Avaliou-se a altura, massa seca da parte aérea e raiz e o número de juvenis de P. brachyurus no interior das raízes. Os resultados demonstram que partir dos 50 dias os tratamentos aplicados na forma sólida foram eficientes no controle de P. brachyurus e ao desenvolvimento das plantas de soja. Aos 75 dias, observa-se que as plantas cultivadas com VERM foram menos prejudicadas, sendo o número de nematoides penetrados 13% e 26% menor que o observado nos adubos ECO e CEBP. Novos ensaios deverão ser realizados utilizando compostos de esterco bovino, resíduos comerciais e o vermicomposto para confirmar o potencial dos fertilizantes orgânicos no controle de P. brachyurus em soja a campo.

Plant-parasitic nematodes devastate a wide range of plant species across the world including many economically important crops such as coffee. Determining the mechanisms that underpin nematode entry and parasitism of the root is of great interest for the design of control strategies. The first aspect of crop protection is to accurately and reliably diagnose the nematode species of concern. A molecular pipeline is described in this thesis that utilises PCR to rapidly detect and quantify the major Meloidogyne and Pratylenchus nematode species that are capable of parasitising coffee. This methodology assessed the prevalence of these species across the major coffee growing regions in Brazil, Vietnam and Indonesia. Distinct profiles of Meloidogyne species were detected across the regions whereas congruent Pratylenchus species were associated with coffee in all three countries. Furthermore, the pathogens were more numerous around intercropped plants such as banana and black pepper compared to coffee, suggesting that these crops may aggravate the issue. There was a high abundance of Meloidogyne in soil in which Pratylenchus was low, suggesting that the success of one genus may deter another. There is a clear widespread, yet differential nematode problem within coffee plantations that is likely to be effecting production and the issue is compounded by local practices and choices of intercrops. The global scale of the problem and the cost to coffee production could be elucidated with wider application of the approach. Plant-nematode interactions must be defined in order to act upon diagnoses from the field. As obligate plant parasites, Meloidogyne and Pratylenchus nematodes must be able to locate and feed from their host in order to survive. The plant cell wall provides protection and support to plant cells and is a major barrier that the nematode must overcome to initiate feeding. This projects shows that Pratylenchus coffeae, a key species detected in the field, regulates the expression of selected cell-wall degrading enzyme genes relative to the abundance of substrate in root exudates, thereby tailoring gene expression to maximise the chances of successful parasitism. Treatment with the substrates directly or with root exudates deficient in the substrates conferred a specific gene expression response with no effect on expression of another cell wall degrading enzyme gene. This indicates that host-specific gene expression in this plant-parasitic nematode is influenced by cell wall components that derive from plant secretion or degradation of root tissue. The illustrated transcriptional plasticity may have evolved as an adaptation for recognition and increased root invasion of a wider range of host species.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Amostras de solo e raízes foram coletadas em plantações de café no estado de São Paulo, com o objetivo de determinar a importância e a ocorrência dos nematóides das lesões na cultura do café. A espécie de Pratylenchus mais freqüente foi P. brachyurus (solo: 13,2 %; raízes: 18,3 %), mas geralmente em baixas densidades. O nematóide das lesões do café, P. coffeae, ocorreu em 5,1 % das amostras de raízes, mas em altas densidades e causando mais danos do que a primeira espécie. Outra espécie, P. vulnus, foi encontrada somente em uma localidade. Este é o primeiro relato de P. vulnus em café. Outros fitonematóides identificados nas amostras foram: Xiphinema brevicolle, Xiphinema sp., Paratrichodorus minor, Paratrichodorus sp.,...
Soil and root samples were collected from coffee plantations in the state of São Paulo, in order to determine the occurrence and importance of lesion nematodes in coffee culture. The most frequent species of Pratylenchus was P. brachyurus (soil: 13,2 %; roots: 18,3 %), but generally in low densities. The coffee lesion nematode, P. coffeae, occurred in 5,1 % of root samples, but in higher densities and causing more damage than the former species. Other species, P. vulnus, was found in one single locality. This is the first report of P. vulnus on coffee. Other phytonematodes identified in the survey were: Xiphinema brevicolle, Xiphinema sp., Paratrichodorus minor, Paratrichodorus sp., Tylenchorhynchus sp., Helicotylenchus dihystera, H. californicus, H. erythrinae, Helicotylenchus sp., Scutellonema sp., Rotylenchulus reniformis, Meloidogyne exigua, M. incognita, M. coffeicola, Meloidogyne sp, Criconemella onoensis, C. ornata, C. sphaerocephala, Criconemella sp., Hemicriconemoides strictathecatus, and Paratylenchus sp. ...(Complete abstract, click electronic access below)

Orientador: Mário Massayuki Inomoto
Resumo: Amostras de solo e raízes foram coletadas em plantações de café no estado de São Paulo, com o objetivo de determinar a importância e a ocorrência dos nematóides das lesões na cultura do café. A espécie de Pratylenchus mais freqüente foi P. brachyurus (solo: 13,2 %; raízes: 18,3 %), mas geralmente em baixas densidades. O nematóide das lesões do café, P. coffeae, ocorreu em 5,1 % das amostras de raízes, mas em altas densidades e causando mais danos do que a primeira espécie. Outra espécie, P. vulnus, foi encontrada somente em uma localidade. Este é o primeiro relato de P. vulnus em café. Outros fitonematóides identificados nas amostras foram: Xiphinema brevicolle, Xiphinema sp., Paratrichodorus minor, Paratrichodorus sp., ...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Soil and root samples were collected from coffee plantations in the state of São Paulo, in order to determine the occurrence and importance of lesion nematodes in coffee culture. The most frequent species of Pratylenchus was P. brachyurus (soil: 13,2 %; roots: 18,3 %), but generally in low densities. The coffee lesion nematode, P. coffeae, occurred in 5,1 % of root samples, but in higher densities and causing more damage than the former species. Other species, P. vulnus, was found in one single locality. This is the first report of P. vulnus on coffee. Other phytonematodes identified in the survey were: Xiphinema brevicolle, Xiphinema sp., Paratrichodorus minor, Paratrichodorus sp., Tylenchorhynchus sp., Helicotylenchus dihystera, H. californicus, H. erythrinae, Helicotylenchus sp., Scutellonema sp., Rotylenchulus reniformis, Meloidogyne exigua, M. incognita, M. coffeicola, Meloidogyne sp, Criconemella onoensis, C. ornata, C. sphaerocephala, Criconemella sp., Hemicriconemoides strictathecatus, and Paratylenchus sp. ...(Complete abstract, click electronic access below)
Doutor

Orientador: Avelino Rodrigues de Oliveira
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Foram mantidas e aumentadas culturas monoxênicas de Pratylenchus , P. penetrans e P. brachyurus. A influência de dois meios de cultura sobre a reprodução dos nematóides em calos de alfafa foi estudada...Observação: O resumo, na integra, podera ser visualizado no texto completo da tese digital
Abstract: Monoxenic cultures of Pratylenchus zeae, P. penetrans and P. brachyurus have been maintained and increased. The influence of two culture media on the nematode reprodllction has been studied...Note: The complete abstract is available with the full electronic digital thesis or dissertations
Mestrado
Bioquimica
Mestre em Biologia

Abstract This chapter discusses the economic importance, geographical distribution, host range, damage symptoms, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated management, and management optimization of Pratylenchus vulnus infesting nut crops in California, USA. Future research requirements and future developments are also mentioned.

Abstract This chapter focuses on the economic importance, host range, geographical distribution, damage symptoms and biology and life cycle of Pratylenchus brachyurus, P. neglectus, P. scribneri and P. zeae infesting sugarcane in South Africa. Information on their interactions with other nematodes and pathogens, the efficacy and optimization of some recommended integrated nematode management programmes and future nematode research requirements are also presented.

Abstract This chapter discusses the economic importance, distribution, host range, damage symptoms, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated management, and management optimization of Pratylenchus penetrans infesting onion. Future research requirements and future developments are also mentioned.

Abstract Pratylenchus penetrans is a cosmopolitan species reported from 69 countries representing every continent except Antarctica. P. penetrans has a wide host range including potato and is found throughout the potato growing region of the northern USA. Most potato fields are infested with the fungus Verticillium dahliae as well as root lesion nematodes, and a disease interaction between the two has been demonstrated for multiple soil types, potato cultivars and production regions. The significance of the interaction between P. penetrans and V. dahliae is that it is synergistic rather than additive. This chapter discusses the economic importance, distribution, symptoms of damage, biology and life cycle, recommended integrated nematode management and management optimization of P. penetrans. Future research requirements are also mentioned.

Abstract This chapter provides information on geographical distribution; host plants; symptoms; biology and life cycle; economic importance; movement and means of dispersal; pest risk analysis; invasiveness rating; management measures, including cultural, host resistance, biological, and chemical control; and detailed account of diagnosis procedures, such as morphological, biochemical, and molecular characterization, of Achlysiella, Hirschmanniella, Nacobbus, Pratylenchus, Radopholus and Zygotylenchus species.

Abstract This chapter provides information on the economic importance, host range, geographical distribution, damage symptoms, biology and life cycle and interactions with other nematodes and pathogens of the root lesion nematode, Pratylenchus thornei, a severe and widespread threat to wheat production in the subtropical grain production region of eastern Australia. Some recommended integrated nematode management practices and future research for nematode resistance breeding are also presented.

Abstract This chapter focuses on the economic importance, host range, geographical distribution, damage symptoms and biology and life cycle of root lesion and root-knot nematodes infesting soyabean in Brazil, i.e. Pratylenchus brachyurus, Meloidogyne javanica and M. incognita. Some information on their interactions with other nematodes and pathogens, efficacy and optimization of some recommended integrated nematode management strategies and future outlook and research requirements for nematode management are also presented.

Abstract This chapter focuses on the economic importance, host range, geographical distribution, damage symptoms and biology and life cycle of the root-knot, reniform and lesion nematodes Meloidogyne incognita, Rotylenchulus reniformis and Pratylenchus brachyurus infesting cotton in Brazil. Information on their interactions with other nematodes and pathogens, the efficacy of some recommended integrated nematode management (INM) programmes and future research requirements and an outlook for INM in Brazil are also presented.

Abstract More than 68 species of plant parasitic nematodes belonging to 24 genera are associated with potato fields from different parts of the world. Among all, two groups of nematodes are important in potato production in Idaho, USA. These include root-knot nematodes (Meloidogyne spp.) and root lesion nematodes (Pratylenchus spp.). This chapter discusses the symptoms and damage, distribution, host range, recommended integrated management (including chemical, cultural and host resistance methods) and interactions with other pathogens of root-knot and root lesion nematodes.

Abstract Soil-borne plant-parasitic nematodes are microscopic, eellike roundworms. The root-knot nematodes (Meloidogyne spp.) and root-lesion nematodes (Pratylenchus vulnus) are among the most damaging in California, which are difficult to control and can spread easily in soil on tools, boots, and infested plants. Root-knot nematodes can attack many different crops, including nut and fruit trees, usually cause unusual swellings, called galls, on affected plants’ roots. It is not easy to recognize the infestations of these nematodes. For instance, researchers need to dig up walnut trees with symptoms, wash or gently tap the soil from the roots, and examine the roots for galls. The nematode extraction procedures, identification, and enumeration under a microscope are tedious and time-consuming. Therefore, in this article, the authors proposed to use a low-cost contactless radio frequency tridimensional sensor “Walabot,” and Deep Neural Networks (DNNs), to perform the early detection of nematodes in a walnut site. Radiofrequency reflectance of walnut leaves from different nematode infestation levels was measured. The hypothesis was that waveforms generated from walnut leaves can estimate the damage caused by nematodes. DNNs with Tensor-Flow were used to train and test the proposed method. Results showed that the Walabot predicted nematode infestation levels with an accuracy of 82%, which showed great potentials for early detection of nematodes.

Verticillium dahliae is an economically important pathogen causing vascular wilt on over 160 plant species. In North America, potato early dying is a significant disease of potato, especially in the midwest and Pacific northwest states. This disease is caused by the fungus Verticillium dahliae and in some cases involves a synergistic interaction with root-lesion nematodes, primarily Pratylenchus penetrans. In Israel, Verticillium wilt occurs in many regions and inflicts serious losses in potato, cotton, and other crops. Objectives of this project were to establish a large collection of isolates of Verticillium dahliae from potato (USA) and several host plants (Israel) and to characterize and compare the isolates with regard to morphology, vegetative compatibility group (VCG), and pathogenic capabilities on several hosts. Isolations were made from 224 commercial lots of certified potato seed tubers from across N. America and 87 potato fields located in the Columbia Basin of Oregon and Washington. A large collection of isolates from central U.S. states already existed. In Israel, 47 field sites were sampled and isolates of Verticillium dahliae were recovered from 13 host plant species and from soil. Potato isolates from N. America were tested for vegetative compatibility and all found to be in VCG 4 with about 2/3 in VCG 4A and the rest in VCG 4B. VCG 4A isolates were significantly more aggressive on potato than VCG 4B isolates and were more likely to interact synergistically with P. penetrans. The Israeli isolates fell into three vegetative compatibility groups. Nearly all (> 90%) VCG2B and VCG 4B isolates were recovered from the northern and southern parts of Israel, respectively, with some overlap in central areas. Several pathotypes were defined in cotton, using cotton and eggplant together as differentials. All VCG 2B isolates from cotton caused severe disease in cotton, while VCG 2A and VCG 4B isolates from several crops were much less aggressive to cotton. When Israeli isolates of VCGs 2A, 2B and 4B were inoculated to potato and tomato, VCG 4B isolates caused much more severe disease on potato and VCG 2A isolates caused much more severe disease in tomato. Differential patterns of pathogenicity and aggressiveness of these VCGs on potato and tomato were consistent regardless of the host plant of origin. Isolates of the same VCG resembled one another more than isolates from different VCGs based on colony and microsclerotial morphology, temperature responses and, partially, in pathogenicity. Vegetative compatibility grouping of V. dahliae in Israel appears closely associated with specific pathogenicity and other phenotypic traits. The absence of VCG 4A in Israel is significant. VCG patterns among Verficillium populations are useful to predict relatedness and pathogenic potential in both countries.