Genetic characterization and pathogenicity of Rhizoctonia solani associated with common bean web blight in the main bean growing area of Argentina

SPEDALETTI Y; APARICIO M; MERCADO CARDENAS G; RODRIGUERO M; TABOADA G; ABAN C; SÜHRING S; VIZGARRA O; GALVAN M

JOURNAL OF PHYTOPATHOLOGY-PHYTOPATHOLOGISCHE ZEITSCHRIFT

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 164 p. 1054 - 1063

0931-1785

Common bean web blight (WB), caused by the fungus Rhizoctonia solani (teleomoph Thanatephorus cucumeris), is among the endemic fungal diseases of major impact in northwestern Argentina (NWA).  This study aimed to analyze the genetic and pathogenic diversity of R. solani in Salta, NWA, where 97 isolates were recovered from commercial bean cultivars and wild beans showing WB symptoms in a major bean production area. The isolates were characterized on the basis of specific-primers, rDNA-ITS sequences, and morphological characteristics. All the isolates were identified as R. solani AG 2-2WB and they exhibited considerable intra-group variation. The phylogenetic tree generated with the ITS sequences confirmed the isolates identification. Aggressiveness of the isolates towards bean seedlings was assessed in the greenhouse. A great variability in virulence was observed among the isolates analyzed. On the basis of the disease reaction on foliar tissues, the isolates were grouped into three virulence categories as follows: weakly virulent (30%), moderately virulent (38%), and highly virulent (32%). However, no correlation between virulence and geographical origin was detected. The information generated in the present study provides initial data on the population variability of the WB pathogen in northwestern Argentina and represents a valuable contribution to regional breeding programs aimed to obtain cultivars with durable resistance.