Web blight is one of the main diseases that affects bean (Phaseolus vulgaris) cultivation. It infects diverse organs at any growth stage of the plant and can be present at different altitudes in a humid tropical climate. The causal agent of this disease is Thanatephorus cucumeris in its sexual stage and Rhizoctonia solani in the anamorph. The objective of this investigation was to characterize molecular isolates of R. solani obtained from bean plants from diverse production regions in Costa Rica and determine their virulence. Fifty-one samples of symptomatic bean plants were collected using a global positioning system. Virulence was evaluated using the detached leaf technique. Isolates were identified using AG 1-IA, AG 1-IB, AG 1-IC, AG 1-ID, AG 2-2, AG 2-2IIIB, AG 2-2IV and AG 4 molecular markers. ITS sequences were obtained and analyzed with BLAST, aligned, and a phylogenetic tree was constructed. A high degree of virulence and genetic variability between isolates was identified and the anastomosis subgroups of isolates were independent of their geographical origin.
Phaseolus vulgaris; anastomosis group (AG); genetic variability; molecular characterization; sclerotium size; virulence
