Meta-analysis of the field efficacy of seed- and soil-applied nematicides on Meloidogyne incognita and Rotylenchulus reniformis across the U. S. Cotton Belt

Meta-analysis was used to compare yield protection and nematode suppression provided by two, seed- and two, soil-applied nematicides against Meloidogyne incognita and Rotylenchulus reniformis on cotton across three years and several trial locations in the United States Cotton Belt. Nematicides consisted of thiodicarb- and fluopyram-treated seed, aldicarb and fluopyram applied in-furrow and combinations of the seed treatments and soil-applied fluopyram. The nematicides had no effect on nematode reproduction or root infection but had a significant impact on seed cotton yield response (¯D) with an average increase of 176 and 197 kg/ha relative to the nontreated control in M. incognita and R. reniformis infested fields, respectively. However, because of significant variation in yield protection and nematode suppression by nematicides, five or six moderator variables [cultivar resistance (M. incognita only), nematode infestation level, nematicide treatment, application method, trial location, and growing season] were used depending on nematode species. In M. incognita infested fields, greater yield protection was observed with nematicides applied in-furrow and seed-applied + in-furrow than solo seed-applied nematicide applications. Most notably of these in-furrow nematicides were aldicarb and fluopyram (>131 g/ha) with or without a seed-applied nematicide compared to thiodicarb. In R. reniformis infested fields, moderator variables provided no further explanation of the variation in yield response by nematicides. Furthermore, moderator variables provided little explanation of the variation in nematode suppression by nematicides in M. incognita and R. reniformis infested fields. The limited explanation by the moderator variables on the field efficacy of nematicides in M. incognita and R. reniformis infested fields demonstrates the difficulty of managing these pathogens with nonfumigant nematicides across the U. S. Cotton Belt.

Prevalence and Molecular Diversity of Plant-Parasitic Nematodes of Yam (Dioscorea spp.) in China, with Focus on Merlinius spp.

There is little information about nematode pests associated with yam in China. Between 2020 and 2021, surveys of yam fields were conducted to investigate the abundance and prevalence of plant-parasitic nematodes in major yam growing areas. A total of 110 bulk soil samples from the yam rhizosphere and 48 yam tubers were collected from seven counties in Jiangxi and Shandong provinces. Standard protocols were used to extract nematodes from soil and tubers and identified at the genus level. In this study, 16 species and 13 nematode genera were recorded. The five most prominent species on the yam rhizosphere according to mean population densities were Pratylenchus coffeae (291/individuals), Meloidogyne (262/individuals), Rotylenchulus reniformis (225/individuals), Merlinius (224/individuals), and Helicotylenchus dihystera (171/individuals). In the tubers, the three most prominent species were Pratylenchus coffeae (415/individuals), Meloidogyne (331/individuals), and Rotylenchulus reniformis (115/individuals). These species were verified with appropriate molecular analysis. The high prevalence of the ectoparasite (Merlinius spp.) on the rhizosphere of yam also revealed that Merlinius spp. May be more important to yam than previously thought. Morphological and molecular analyses further confirmed the identity of the species as Merlinius brevidens and were characterized for the first time on yam in China. Minor morphometrical differences (slightly longer body and stylet) were observed in Chinese populations of M. brevidens compared to the original description. Additionally, this study reveals that M. brevidens isolated from China showed a higher nucleotide sequence in the ITS region compared to M. brevidens populations from India. This finding provides baseline information on the nematode pest occurrence on yam in China and calls for effective management.

Evaluation of Cotton Cultivar and At-Plant Nematicide Application on Seasonal Populations of Reniform Nematode

The reniform nematode, Rotylenchulus reniformis (Linford and Oliveira), remains a common, widespread nematode pest of cotton across the southern United States. Trials were conducted during 2017 at three non-irrigated locations: one location in Hamilton, MS, and two locations in Tchula, MS, in field settings with a history of cotton production and documented economically-damaging reniform nematode populations. Trials were designed to evaluate the response of two cotton cultivars to in-furrow nematicides consisting of aldicarb, 1,3-dichloropropene, and a non-treated control applied for nematode suppression. No significant interactions between cotton cultivar and nematicide were observed. However, treatment with 1,3-dichloropropene produced greater plant biomass, and plant height compared to aldicarb-treated cotton and the nontreated. Nematode densities were suppressed with the use of 1,3-dichloropropene compared to aldicarb and the non-treated control. The use of 1,3-dichloropropene resulted in positive early-season plant growth responses; however, these responses did not translate into greater yield.

SELEÇÃO DE MARCADORES RAPD POLIMÓRFICOS PARA O ESTUDO DA DIVERSIDADE GENÉTICA DO FITONEMATÓIDE ROTYLENCHULUS RENIFORMIS

Introdução: O melão Cucumis melo L. é um fruto de grande importância econômica, com amplo consumo no mercado nacional e internacional. No Brasil, a região Nordeste destaca-se como a principal produtora dessa fruta. No entanto, a espécie sofre com diversos ataques ocasionados por uma vasta gama de pragas que estão associadas a esses cultivos. Dentre elas, está o fitonematóide Rotylenchulus reniformis, responsável por reduzir a qualidade e quantidade das produções agrícolas. O estudo da variabilidade genética desse organismo é relevante, pois as variações gênicas entre o fitopatógeno podem estar relacionadas à diferentes níveis de patogenicidade. A seleção de marcadores de DNA informativos representa uma etapa significativa neste tipo de estudo, pois possibilitará a economia de recursos e tempo investidos. Objetivo: O presente trabalho teve como objetivo a identificação de marcadores RAPD polimórficos para futuros estudos de diversidade genética dessa espécie. Material e Métodos: Para isso, o DNA do fitonematóide foi inicialmente extraído com kit de extração de DNA NucleoSpinTissue (Macherey-Nagel). Posteriormente, 80 primers RAPD foram testados quanto ao seu nível de polimorfismo e qualidade de bandas amplificadas gerada nessa espécie. Resultados: Como decorrência da triagem dos 80 iniciadores RAPD, foi constatado que 71 desses não amplificaram, ou obtiveram bandas fracas e não reprodutíveis, sendo selecionados somente nove iniciadores. Desse modo, 70 bandas foram amplificadas, com média de 7,78 por iniciador, das quais 67 foram polimórficas, gerando 95,81% de polimorfismo. Dos nove iniciadores, seis apresentaram 100% de polimorfismo. O iniciador menos eficiente foi o OPA-03. Dois iniciadores apresentaram maior quantidade de bandas amplificadas (OPA-16 e OPAA-04) sendo o iniciador OPAA-04 mais informativo (100% de polimorfismo). Conclusão: A identificação desses marcadores polimórficos ajudará a compreender, em estudos posteriores, a correlação da diversidade genética com interações planta-patógeno desse fitonematóide.

Molecular Diagnosis and Evolutionary Relationship Analysis Of Plant Parasitic Tea Garden Nematodes From Different Tea Estates In Sylhet Region of Bangladesh

Nematodes from plant-parasitic sources are ever-present and incidental to plant growth as well as crop production. The damage of tea gardens caused by nematode is often non-specific and easily confused with symptoms. The present study determined the parasitic and non-parasitic nematodes population in different tea gardens of the Sylhet region by their morphological and partial molecular characterization. Out of 13 tea gardens, it was observed that BTRI, Karimpur, Mathiura, and Tarapur tea garden has the highest number of parasitic and non-parasitic nematodes. After PCR amplification, DNA bands with desired amplicon size were detected by gel electrophoresis. Among thirteen soil samples, nematodes from Malnichara, Karimpur, BTRI, Mathiura , and Finlay had partially confirmed the presence of rootknot nematode (Meloidogyne spp.), root-lesion nematode (Pratylenchus brachyurus), burrowing nematode (Radopholus similis), reniform nematode (Rotylenchulus reniformis) and lance nematode (Hoplolaimus columbus) consequently based on approximately base pair of 1.7, 1.1 and 0.52 kb (different Meloidogyne spp.) 0.52, 0.52, 0.25 and 2.3 kb of specific genes. From evolutionary analysis, it might be said that Meloidogyne species are strongly related with each other making clusters except Meloidogyne natalie where this one is closely related with Hoplolaimus columbus in their evolutionary relationship as remaining others (Rotylenchulus reniformis, Radopholus similis, Pratylenchus brachyurus) are in different clusters in the same clade and this result could be confirmed after sequencing. J. Bio-Sci. 29(1): 101-109, 2021 (June)

Biological control of nematodes infecting eggplant in Egypt

Background Eggplant is of great renown in Egypt and worldwide as it is favorable and high value vegetable crop. Yet, many plant-parasitic nematodes (PPNs) can penetrate the roots of this plant and feed on it, causing heavy losses in its yield. Meloidogyne spp. (root-knot nematodes, RKNs) and Rotylenchulus reniformis rank high among these parasites in Egypt. Main body of the abstract This review compiles PPN ecology, biology and economic value from the pest management point of view. Applying production practices and other preventive methods against PPNs should be a priority. Accelerating and unprecedented public concern about excessive use of chemical nematicides leading to health problems, development of pest resistance, and environmental contamination, has boosted interest in developing eco-friendly biologicals as safe substitutional materials. Hence, safe biological control agents (BCAs) are reviewed herein to prove that they are quintessential to nematode control on eggplant in Egypt. Thus, BCAs should reliably operate with other agricultural inputs in integrated pest management programs against eggplant nematodes. Short conclusion A few paradigms are shown herein which foster BCA practical use via additive or synergistic relation with compatible inputs such as compost, chemicals, and manure. Upgrading their delivery techniques, beneficial interaction and persistence in fields with nematode-infected eggplants should be broadly tested and greatly disseminated.

Root-knot and reniform nematodes: double trouble for soybeans in the southern United States.

This chapter focuses on the economic importance, host range, geographical distribution, symptoms of damage and biology and life cycle of root-knot and reniform nematodes (Meloidogyne spp. and Rotylenchulus reniformis) infesting soyabeans in southern USA. Some information on the efficacy and optimization of some recommended integrated nematode management practices and future outlook and research requirements are also presented.