Phytonematodes infesting common bean fields in Brazil, and pathogenicity tests with Pratylenchus brachyurus

Phytonematodes are among the main pathogens of the common bean. In general, control practices that aim to control these pathogens have not been regularly adopted in Brazil. The objectives of the present study were to evaluate the occurrence of phytonematodes in dry bean fields in Paraná and São Paulo states and estimate the pathogenicity of Pratylenchus brachyurus to dry bean in glasshouse experiments. Root and soil were sampled for nematode extraction, identification and estimation of population density. Four glasshouse experiments with different initial population densities were carried out to evaluate the effect of P. brachyurus on the growth of dry bean plants. Six species of phytonematodes were detected, namely Helicotylenchus dihystera, P. brachyurus, Pratylenchus crenatus, Meloidogyne javanica, Meloidogyne incognita and Rotylenchulus sp. The spiral nematode H. dihystera was found in all samples and was the most abundant species in both states. The lesion nematode P. brachyurus was also frequent, reaching 94% in Paraná and 100% in São Paulo. The root-knot nematodes and Rotylenchulus sp. were reported only in São Paulo fields (45% and 18% frequency, respectively), and P. crenatus only in Paraná (12%). The most abundant nematode in the soil was H. dihystera, and in roots was P. crenatus. It was demonstrated that densities of 6.66 specimens of P. brachyurus per cm3 of soil provoke visible and measurable root decay. In conclusion, survey data showed low phytonematode densities and pathogenicity tests demonstrated that densities above 6.67 specimens of P. brachyurus per cm3 of soil cause damage to the dry bean roots.

Óleo essencial das folhas e frutos de Schinus terebinthifolius raddi no controle de Pratylenchus zeae / Essential oil from the leaves and fruits of Schinus terebinthifolius raddi in the control of pratylenchus zeae / Aceite esencial de las hojas y frutos de Schinus terebinthifolius raddi en el control de pratylenchus zeae

Os óleos essenciais (OEs) são metabólitos secundários que podem apresentar potencial no controle alternativo de nematoides. Assim objetivou-se testar o OE de pimenta rosa no controle de P. zeae em condições in vitro e na cultura do milho. O OE foi extraído por hidrodestilação, utilizando massa fresca das folhas e frutos maduros. O experimento in vitro foi instalado em arranjo fatorial 8x2, sendo oito concentrações (0,00, 7,80, 15,00, 31,00, 62,00, 125,00, 250,00 e 500,00 µg mL-1) e OE das folhas e dos frutos. As unidades experimentais foram tubos de ensaio com capacidade para 5mL, contendo 1 mL de cada concentração, e 1mL de suspensão de 50 nematoides. Decorrido 48 horas avaliou-se a porcentagem de mortalidade. O experimento em casa de vegetação foi instalado em arranjo fatorial 5x2, sendo cinco concentrações (0,00, 7,8, 15,0, 31,0 e 62,0 µg mL-1) e OEs (Folhas e frutos). As unidades experimentais constituíram-se por vasos com capacidade para 1,5 kg, os quais foram inoculados com 2000 e 1800 nematoides e semeados com sementes de milho tratadas com as concentrações dos OEs. Os OEs e as concentrações avaliadas apresentaram porcentagem de mortalidade em condições in vitro e reduziram a população de P. zeae, em casa de vegetação, o OE dos frutos promoveu maior mortalidade nos testes in vitro. Sendo assim os OEs demonstraram potencial no controle de fitonematoide, porém, há a necessidade de estudos a aplicabilidade dos mesmos.(AU)

Essential oils (EOs) are secondary metabolites that may present potential for an alternative control of nematodes. The purpose of this study was to test the EO of pink peppercorn in the control of P. zeae under in-vitro conditions and in the maize crop. Essential Oil was extracted by hydro-distillation using fresh leaf mass and mature fruits. The in-vitro experiment was installed in an 8x2 factorial arrangement, with eight concentrations (0.00, 7.8, 15.0, 31.0, 62.0, 125.0, 250.0 and 500.0 µg mL-1) and EO from leaves and fruits. The experimental units were 5-mL test tubes containing 1 mL of each concentration and 1 mL of suspension of 50 nematodes. The mortality percentage was evaluated after 48 hours. The greenhouse experiment was installed in a 5x2 factorial arrangement, with five concentrations (0.00, 7.8, 15.0, 31.0 and 62.0 µg mL-1) and EOs (leaves and fruits). The experimental units consisted of 1.5-kg capacity vases, which were inoculated with 2000 and 1800 nematodes, and seeded with corn seeds treated with EO concentrations. The EOs and concentrations evaluated presented a mortality percentage under the in-vitro conditions and reduced the P. zeae population in the greenhouse, while the EO from the fruits promoted higher mortality in the in-vitro tests. Therefore, EOs have shown potential in the control of phytonematodes, but further studies are required for their applicability.(AU)

Los aceites esenciales (OEs) son metabolitos secundarios que pueden presentar potencial en el control alternativo de nematodos. Así se objetivó probar el OE de pimienta rosa en el control de P. zeae en condiciones in vitro y en el cultivo del maíz. El OE fue extraído por hidrodestilación utilizando masa fresca de las hojas y frutos maduros. El experimento in vitro fue instalado en un arreglo factorial 8x2, siendo ocho concentraciones (0,00, 7,80, 15,00, 31,00, 62,00, 125,00, 250,00 y 500,00 µg mL-1) y OE de las hojas y de los frutos. Las unidades experimentales fueron tubos de ensayo con capacidad para 5 mL, conteniendo 1 mL de cada concentración, y 1 mL de suspensión de 50 nematodos. Después de 48 horas se evaluó el porcentaje de mortalidad. El experimento en casa de vegetación fue instalado en arreglo factorial 5x2, siendo cinco concentraciones (0,00, 7,8, 15,0, 31,0 y 62,0 µg mL-1) y OEs (Hojas y frutos). Las unidades experimentales se constituyeron por floreras con capacidad para 1,5 kg, los cuales fueron inoculados con 2000 y 1800 nematodos y sembrados con semillas de maíz tratadas con las concentraciones de los OEs. Los OEs y las concentraciones evaluadas presentaron un porcentaje de mortalidad en condiciones in vitro y redujeron la población de P. zeae, en casa de vegetación, el OE de los frutos promovió mayor mortalidad en las pruebas in vitro. Así los OE demostraron potencial en el control de fitonematodos, sin embargo, hay la necesidad de estudios a la aplicabilidad de los mismos.(AU)