Navegando por Autor "Silva, Rodrigo V."

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Characterization of Meloidogyne incognita populations from São Paulo and Minas Gerais state and their pathogenicity on coffee plants
(Sociedade Brasileira de Fitopatologia, 2011) Oliveira, Dagoberto S.; Oliveira, Rosângela D’Arc Lima; Silva, Débora G.; Silva, Rodrigo V.
Meloidogyne incognita is one of the most aggressive and harmful plant-parasitic nematodes attacking coffee plantations in Brazil. However, populations from Minas Gerais state (MG) do not incite disease on coffee plants as strongly as populations from São Paulo state (SP). This study aimed to compare the capacity to incite disease on coffee plants from SP and MG-populations based on penetration and post-infective development of second-stage juveniles (J2) stage. Both populations were confirmed as M. incognita by using esterase phenotype I1 and species-specific PCR. Physiologically they were classified as race 2 by differential host test. Susceptible (C. Arabica ‘Catuaí Vermelho IAC 44’) and resistant coffee seedlings (C. canephora ‘Apoatã IAC 2258’) were inoculated with J2 and assessed for penetration and development from 2nd to 40th day after inoculation. Although the penetration rate of the J2 from both populations was higher in susceptible than in resistant seedlings, the SP-population showed a higher penetration than the MG-population for both variables. Post-infective development proceeded only in individuals of the SP-population in susceptible seedlings. The incompatibility between the MG-population and coffee seedlings was evident at the penetration phase, which was also followed by post-penetration resistance factors leading to significant J2 emigration, impeding nematode establishment.
Defense responses to Meloidogyne exigua in resistant coffee cultivar and non-host plant
(Sociedade Brasileira de Fitopatologia, 2013) Silva, Rodrigo V.; Oliveira, Rosângela D.L.; Ferreira, Patrícia S.; Ferreira, Aline O.; Rodrigues, Fabrício A.
The resistance of coffee plants to Meloidogyne exigua is conferred by the gene Mex-1. However, the mechanisms of resistance still need to be clarified. Therefore, the penetration, development and reproduction of two populations of M. exigua (M1, isolated from the coffee plant and M2, from rubber tree) in susceptible (Coffea arabica ‘Catuai’) and resistant (C. canephora ‘Apoatã’) cultivars were studied. A greater quantity of J2 from M1 penetrated the susceptible cultivar, but there was no difference between the cultivars for M2. Although the resistant coffee cultivar formed some galls, the nematode did not reproduce. M2 did not induce the formation of galls or the production of eggs in either cultivars. Events related to hypersensitive reaction (HR) were observed as well as other defense responses of the coffee cultivar against M. exigua, which inhibited the formation of the feeding site, provoked emigration of the J2 and delayed or inhibited development and reproduction. The response of the non-host plant was more effective, because it did not allow development of the nematode or, consequently, its reproduction. It was concluded that the coffee cultivar’s resistance to M. exigua is not restricted to HR, but rather to a set of defense responses, both constitutive and induced, expressed after nematode penetration, especially phenolic-like compounds.
Respostas de genótipos de Coffea spp. a diferentes populações de Meloidogyne exigua
(Sociedade Brasileira de Fitopatologia (SBF), 2007-08-14) Silva, Rodrigo V.; Oliveira, Rosângela D. L.; Pereira, Antonio A.; Sêni, Dalila J.
Em Meloidogyne exigua, um dos principais patógenos do cafeeiro no Brasil, já foram observadas variabilidade bioquímica, molecular, morfológica e fisiológica. No entanto, a expressão desta variabilidade quanto à virulência a genótipos de cafeeiro não é bem conhecida. O objetivo deste trabalho foi estudar o efeito de populações de M. exigua, as quais exibiam diferentes fenótipos de esterase e preferências por hospedeiros, em 25 genótipos de cafeeiro, com o propósito de se conhecer melhor a interação de biótipos desse nematóide com o gênero Coffea. Seis mudas de cafeeiro por tratamento foram inoculadas no estádio de 3 a 4 pares de folhas definitivas com 5.000 ovos de cada população de M. exigua por planta. O número de galhas e ovos por sistema radicular e a biomassa da matéria fresca das raízes foram avaliados aos 110 dias após a inoculação. Em função da reação frente às populações de M. exigua, os genótipos de Coffea spp. foram classificados em 14 suscetíveis, 5 imunes e 6 segregantes. Estes últimos segregaram de maneira diferenciada conforme a população do patógeno, evidenciando a existência de variabilidade intraespecífica em relação à virulência ao cafeeiro. Assim, o uso de diferentes populações desse patógeno, que englobem essa variabilidade é fundamental no desenvolvimento de cultivares resistentes.