A novel report of Rhizoctonia solani AG-4 HG-I associated with damping-off and wilt of quinoa (Chenopodium quinoa) in India

Abstract

Quinoa, Chenopodium quinoa, was domesticated first in the Andean countries of South America and has been widely cultivated in most countries due to its unique nutritional value and health benefits. In fields, characteristic wilting and girdling symptoms on stems of quinoa plants were observed in Bengaluru and Chamarajanagara districts, Karnataka, India. The associated pathogen was isolated, purified and identified as Rhizoctonia sp. based on cultural and morphological characterization and nuclear staining revealed a multi-nuclei condition of the pathogen. Molecular and phylogenetic analysis with internal transcribed spacer (ITS) region supported by cultural morphological characteristics revealed Rhizoctonia solani as a causal agent and its anastomosis group AG-4 HG-I confirmed using specific primers for each anastomosis group and sub-group. A pathogenicity test combined with pathogen re-isolation and identification was carried out to validate Koch's postulates. Cultural characterization revealed that potato dextrose agar (PDA) at 30 °C with pH 7 was ideal for better growth of R. solani. To the best of our knowledge, this is the first report of damping-off and wilt caused by R. solani on C. quinoa in India.