Resumo

BANUELOS-BALANDRAN, José Jaime  e  MAYEK-PEREZ, Netzahualcóyotl. Nondestructive evaluation of pathogenicity of Macrophomina phaseolina (Tassi) Goid. on bean (Phaseolus vulgaris L.). Rev. mex. fitopatol [online]. 2008, vol.26, n.1, pp.71-75. ISSN 2007-8080.

Genetic improvement to obtain common bean (Phaseolus vulgaris) resistant cultivars to charcoal rot (Macrophomina phaseolina) must have methodologies which allow to evaluate disease damage in a cheap, reliable, and fast way. In this work, the expression of infection by M. phaseolina was evaluated in two common bean cultivars (BAT 477 and Pinto UI-114) with contrasting reactions to the fungus, using three "detached leaf" in vitro inoculation methods: one cm diameter leaf discs, simple or cotyledonal leaves, and folioles from trifoliated leaves. Methods were compared with infection data derived from two "conventional" methods: seedling inoculation with infested rice seeds in greenhouse and in vitro seed culture in PDA colonized with the fungus. The three methods of detached leaf produced disease symptoms and discriminated between resistance and susceptibility reactions to M. phaseolina. The use of cotyledonal leaves is recommended to assess the reaction to M. phaseolina in beans, because the method is simple, fast, and reliable.

Palavras-chave : Detached leaf; in vitro inoculation; charcoal rot.

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