Morphological, Molecular, and Pathogenic Characterization of Rhizoctonia solani Isolates Associated with Bean Drying in Northern Sinaloa, Mexico.

Abstract

Objective: The objective of this study was to characterize, using morphology, DNA sequence analysis, and pathogenicity, R. solani isolates associated with bean plants with root rot symptoms in commercial plots in northern Sinaloa.

Design/methodology/approach: During the 2020-2021 cycle, diseased plants infected by Rhizoctonia were collected in the municipalities of Ahome, El Fuerte, and Guasave. Pure fungal isolates were obtained in specific media; which were morphologically characterized in PDA medium and preserved. Subsequently, the pathogenicity of the isolates was evaluated and they were molecularly identified. Genomic DNA was extracted from the isolates, part of the RPB2 gene was amplified by PCR, and the amplified products were sequenced.

Results: Phylogenetic analysis with RPB2 sequence data confirmed the identification of 63 isolates as R. solani and allowed them to be assigned to the anastomosis group (AG): AG-4. Of the total isolates analyzed, 86% correspond to the AG-4 HGI anastomosis subgroup and 14% to the AG-4 HGIII subgroup. In pathogenicity, the percentage of germination and severity of the isolates were evaluated, showing different levels of pathogenicity.

Limitations of the study/implications: None.

Findings/conclusions: Rhizoctonia solani AG-4 anastomosis subgroups HGI and HGIII are associated with bean drying in northern Sinaloa. Therefore, this study will serve as a basis for other studies that generate control strategies for this pathogen.