Morphocultural characterization of alternaria species-groups asociated to wheat diseases in Argentina

Abstract

Forty isolates of Alternaria from wheat plants were characterized into species-group considering the sporulation pattern, morphology of conidia, patogenicity and toxins production. For identification PCA media was used and the isolates were classified according the sporulation pattern, morphology of conidia/conidiophores and according the colony color on DRYES media. Four species-groups of Alternaria were determined, A. alternata, A. arborescens, A. infectoria, and A. tenuissima groups. This is the first report of A. arborescens on wheat in Argentina. Morphocultural identification was corroborated by molecular analysis PCR- ITS and comparison of isolates with standard strains belonging to international culture collections. Inoculations on wheat grains showed the patogenicity of isolates and symptoms of discoloration, blight and spots on leaves, radicular necrosis and weakness of emerged plants. Wheat cultivars showed different response to the infection according each particular isolate inoculated.  In general a correlation between each species-group and each kind of symptom could been shown The infectoria group has the most virulent strains that induce the highest severity on all tested cultivars. Toxins production highlight the micotoxicologic risk associated to this fungi considering they play a rol in pathogenesis and no current regulations exists in Argentina or in the rest of the world. A. arborescens is registered by first time associated to wheat plants in Argentina.

Keywords: Alternaria complex, wheat, species-group