Identification and pathogenicity of Rhizoctonia solani AG-4 causing root rot on chickpea in Turkey

Abstract

In the 2016-17 growing seasons, surveys were conducted in the Isparta, Uşak, Kütahya and Denizli provinces of Turkey to identify the Rhizoctonia solani AG-4 associated with root and crown rot of chickpea. A total of 75 isolates of Rhizoctonia were obtained from surveyed areas. Visual diagnostic, isolation and microscopic observation identified the causal organism as R. solani. Sequence data of the ITS rDNA region confirmed the species identity and revealed that the anastomosis group of the 23 isolates were AG-4 HGII. The isolates were variable in their morphological characters. The sequences generated during this study were clustered in the same branch with the reference isolates of R. solani AG-4 HGII based on their ITS sequencing on chickpea and the isolate grouping was not related to their geographic origins or virulence pattern. Pathogenicity tests revealed that all AG-4 isolates were pathogenic on chickpea and the disease severity values of 23 isolates varied between 42.8% and 100%. Based on the virulence, the isolates were grouped into two categories: 5 of them exhibited moderately virulence and 18 of them exhibited highly virulence reaction on chickpea. The high virulent isolate level (>50% disease severity) was determined as 78.2% of all 23 isolates. This is the first report of R. solani AG-4 as a pathogen of chickpea in Turkey.