Resistência do cafeeiro a Meloidogyne exigua: mecanismos de natureza genética e potencializados pelo silício

• Ano de defesa: 2009
• Autor(a) principal: Silva, Rodrigo Vieira da
• Orientador(a): Oliveira, Rosângela D arc de Lima
• Banca de defesa: Ferraz, Silamar , Oliveira, Antônio Carlos Baião de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Fitopatologia
• Departamento: Etiologia; Epidemiologia; Controle
• País: BR
• Palavras-chave em Português: Café; Resistência a nematóides-das-galhas; Melhoramento genético; Controle integrado; Silício; Fenóis; Enzimas; Lignina
• Palavras-chave em Inglês: Coffee; Resistance to-the-knot nematodes; Breeding; Integrated control; Silicon; Phenols; Enzyme; Lignin
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA
• Link de acesso: http://locus.ufv.br/handle/123456789/1034

Meloidogyne exigua is considered the one of the most important pathogens of coffee in Brazil. Nowdays, coffee resistance to this nematode is known to be confered by the dominant gene Mex-1, but the mechanisms of coffee resistance to M. exigua still need to be investigated. Therefore, this study aimed to evaluate the defense responses of coffee to M. exigua, either genetic or potentiated by silicon (Si), besides the effect of this element on nutrients uptake and content in roots and shoots of coffee seedlings. The following variables were evaluated: penetration, postembryonic development, and reproduction of M. exigua populations that differ in their capacity of infect coffee roots as well as the histopathology of roots from plants inoculated with the nematode. The content of Si on roots and its effect on M. exigua control, besides the analysis of some biochemical variables, possibly potentiated by this element, were also studied. It was demonstrated that coffee resistance to M. exigua is not only due to the hypersensitive response (HR), but to a set of defense responses, constitutive and/or inducible, after nematode penetration that strongly inhibits the formation of feeding sites. This dramatically causes J2 migration and slows down or inhibits nematode development and reproduction. Furthermore, plants showing non-host resistance were different from the resistant ones considering that no evidence of HR was observed on the former. The first scientific evidence of Si uptake by coffee roots and its positive effect on both plant development and nematode control were demonstrated in this study. Coffee roots of plants from "Catuaí Vermelho IAC 44" cultivar had Si content up to 1%. This Si content is quite higher considering that coffee is a dicotyledonous plant species. Silicon positively influenced the uptake and the content of some nutrients on coffee roots and shoots, besides increasing coffee roots resistance to nematode infection. The highest activity of peroxidases, polyphenoloxidases, and phenylalanin ammonia-liases, besides the great concentration of lignin in roots of both resistant and susceptible plants supplied with Si clearly indicates that these biochemical mechanisms of resistance were associated with both genetic and Si-mediated resistance of coffee to M. exigua. Results provided in this study support the conclusion that application of Si increases coffee resistance against infection by M. exigua by affecting nematode parasitism and enhancing some biochemical mechanisms of defense responses.