Crop rotation in center-pivot for phytonematode control: density variation, pathogenicity and crop loss estimation

Crop rotation in center-pivot for phytonematode control: density variation, pathogenicity and crop loss estimation A field study conducted over three consecutive years, on a farm using crop rotation system under center-pivot and infested with the nematodes Pratylenchus brachyurus, P. zeae, Meloidogyne incognita, Paratrichodorus minor, Helicotylenchus dihystera, Mesocriconema ornata and M. onoense, demonstrated that intensive crop systems provide conditions for the maintenance of high densities of polyphagous phytonematodes. Of the crops established on the farm (cotton, maize, soybean and cowpea), cotton and soybean suffered the most severe crop losses, caused respectively by M. incognita and P. brachyurus. Since maize is a good host for both nematodes, but tolerant of M. incognita, its exclusion from cropping system would be favorable to the performance of cotton, soybean and cowpea. Results from experiments carried out in controlled conditions confirmed the pathogenicity of P. brachyurus on cotton. Additional management with genetic resistance was useful in fields infested with M. incognita, although the soybean performance was affected by low resistance of the cultivars used for P. brachyurus. In conclusion, crop rotation must be carefully planned in areas infested with polyphagous nematodes, specifically in the case of occurrence of two or more major pathogenic nematodes.

Nematicidal effect of volatile organic compounds (VOCs) on the plant-parasitic nematode Meloidogyne javanica

Previous studies have demonstrated that volatile organic compounds (VOCs), produced by the yeast Saccharomyces cerevisiae, were able to inhibit the development of phytopathogenic fungi. In this context, the nematicidal potential of the synthetic mixture of VOCs, constituted of alcohols and esters, was evaluated for the control of the root-knot nematode Meloidogyne javanica, which causes losses to crops of high economic value. The fumigation of substrate containing second-stage juveniles with VOCs exhibited nematicidal effect higher than 30% for the lowest concentration tested (33.3 µL g-1 substrate), whereas at 66.6 and 133.3 µL g-1 substrate, the nematode mortality was 100%. The present results stimulate other studies on VOCs for nematode management.

Meloidogyne javanica control by Pochonia chlamydosporia, Gracilibacillus dipsosauri and soil conditioner in tomato

Organic matter plays a fundamental role in the antagonistic activity of microorganisms against phytonematode populations on the soil. In this study, the compatibility between the fungus Pochonia chlamydosporia (Pc-12) and the rhizobacterium Gracilibacillus dipsosauri (MIC 14) was evaluated in vitro, as well as the effect of the fungus at the concentration of 5,000 chlamydospores per gram of soil, rhizobacterium at 4.65 x 10(9) cells/g of soil, and the soil conditioner Ribumin® at 10 g/pot, either alone or in combination, against Meloidogyne javanica population in tomato plants (3,000 eggs/pot). A suspension of water or Ribumin® alone was applied on the soil as negative control, while a suspension of nematode eggs was applied as positive control. The reduction in the number of galls in roots per plant was 48 and 41% for the treatments Ribumin + MIC 14 + Pc-12 and MIC 14 + Pc-12, respectively. Regarding to the number of eggs per plant, MIC 14 and Pc-12 + Ribumin led to a reduction by 26 and 21%, respectively, compared to the control treatment. Interaction between the nematophagous fungus and the rhizobacterium was positive for the nematode control, even though G. dipsosauri inhibited P. chlamydosporia growth by up to 30% in in vitro tests.

Differential in vitro pathogenicity of predatory fungi of the genus Monacrosporium for phytonematodes, free-living nematodes and parasitic nematodes of cattle

In vitro tests were carried out on the pathogenicity of nine isolates of the predatory fungi of the genus Monacrosporium (5 M. sinense isolates, 3 M. appendiculatum and 1 M. thaumasium isolate) for a phytonematode (second stage juveniles from Meloidogyne incognita, race 3), a free-living nematode (Panagrellus spp), and two gastrointestinal parasitic nematodes of cattle (infective larvae of Cooperia punctata and Haemonchus placei). A suspension containing 2,000 nematodes from each species was added to Petri dishes containing fungi and grown on 2% water-agar medium at 25oC in the dark for up to 7 days. The dishes were examined every other day for 7 days and predation-free nematodes were counted. The results showed that the free-living nematodes, Panagrellus spp, were the most susceptible (P<0.05), followed by the phytonematode M. incognita, while the controls were ³98.5% viable. However, a variable susceptibility of the nematodes to different fungi was observed. This indicates that the use of predatory fungi for the environmental control of nematodes will be limited by the multiplicity of nematodes in the environment and their differential susceptibility to fungal isolates of the same genus.

Detecção de Heterodera glycines em plantio de soja mediante espectrorradiometria no visível e infravermelho próximo

O ataque do nematóide de cisto da soja, Heterodera glycines, limita o potencial de expansão e maior produtividade de áreas plantadas com soja (Glycine Max). O conhecimento da distribuição espacial desse patógeno na lavoura é fundamental, para elaboração de estratégias de manejo. A área em estudo estava localizada em lavoura de soja, variedade BRS133, localizada no Município de Florínea, SP, com solos naturalmente infestados por H. glycines. Foram obtidas medidas de espectrorradiometria de campo, 112 dias após o plantio, nas regiões do visível e do infravermelho próximo do espectro eletromagnético, a fim de se conhecer o padrão da resposta espectral de plantas atacadas pelo fitonematóide. Paralelamente, foram retiradas amostras de solo e encaminhadas ao Laboratório de Nematologia, Departamento de Fitossanidade da Universidade Estadual Paulista Júlio de Mesquita Filho, Campus de Jaboticabal, onde foram processadas para determinação da densidade populacional do nematóide. As medidas do espectrorradiômetro foram transformadas em índice vegetativo, com diferença normalizada (NDVI), que foi relacionado com a densidade populacional do nematóide, peso da matéria fresca e número de vagens por planta. Observou-se que diferentes densidades de população estão diretamente relacionados com a resposta espectral das plantas expressa, através dos valores do NDVI.

Reação de clones de umezeiro (Prunus mume Sieb. et Zucc.) e cultivares de pessegueiro [Prunus persica (L.) Batsch] ao nematóide anelado Mesocriconema xenoplax (Nemata: Criconematidae)

Com o objetivo de avaliar a reação de clones de umezeiro (Prunus mume Sieb. et Zucc.) e cultivares de pessegueiro [Prunus persica (L.) Batsch] ao nematóide anelado Mesocriconema xenoplax (Raski) Loof & de Grise, realizou-se o presente estudo em casa de vegetação do Departamento de Fitossanidade da FCAV/UNESP, Câmpus de Jaboticabal-SP. As plantas foram mantidas em vasos de cerâmica com 6 litros de capacidade, contendo uma mistura de solo e areia (1:1, v/v), previamente autoclavada a 121°C e 1kgf.cm-2 por 2 horas. Cada planta foi inoculada com 10mL de uma suspensão de 200 M. xenoplax por mL. Com os resultados obtidos, após 105 dias da inoculação, pode-se concluir que os Clones 05; 10 e 15 de umezeiro e as cultivares Okinawa e Aurora-1 de pessegueiro são suscetíveis a M. xenoplax. A cultivar Aurora-1 apresentou maior Fator de Reprodução (93,06).

Reação de maracujazeiro amarelo a Meloidogyne Incognita Raça 3

This study concerned the reaction of yellow passion fruit ‘Maguary’ and ‘Afruvec’ to the phytonematode Meloidogyne incognita race 3 in greenhouse conditions. An entirely randomized experimental design with 3 treatments (‘Maguary’, ‘Afruvec’, and tomato cv. ‘Rutgers’) and 4 repetitions was used, each plot consisting of 1 vase containing 1 plant. After 6 months, an evaluation was made of the index of galls and egg mass in the yellow passion fruit varieties and in the tomato cv. ‘Rutgers’. The classification of resistance to the phytonematode was made by criterion of the reproduction factor (RF). ‘Maguary’ presented a zero index of galls and egg mass, while ‘Afruvec’ showed a low index of galls and egg mass in relation to the tomato cv. Rutgers. According to the RF, ‘Maguary’ was characterized as immune to the phytonematode, while ‘Afruvec’ was resistant, and the tomato cv. ‘Rutgers’ was susceptible.

Estudo genético de populações de soja com fonte de resistência à Heterodera glycines (raça 3) oriundas de topocruzamentos tipo alimento x tipo grão

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nematicidal effect of volatile organic compounds (VOCs) on the plant-parasitic nematode Meloidogyne javanica

Previous studies have demonstrated that volatile organic compounds (VOCs), produced by the yeast Saccharomyces cerevisiae, were able to inhibit the development of phytopathogenic fungi. In this context, the nematicidal potential of the synthetic mixture of VOCs, constituted of alcohols and esters, was evaluated for the control of the root-knot nematode Meloidogyne javanica, which causes losses to crops of high economic value. The fumigation of substrate containing second-stage juveniles with VOCs exhibited nematicidal effect higher than 30% for the lowest concentration tested (33.3 µL g-1 substrate), whereas at 66.6 and 133.3 µL g-1 substrate, the nematode mortality was 100%. The present results stimulate other studies on VOCs for nematode management.