Evaluation of soybean genotypes for resistance to collar rot (Sclerotium rolfsii) under field and glasshouse condition

Soybean is the prime leguminous oilseed crop in India. Collar rot of soybean (CRS) caused by Sclerotium rolfsii is one of the major diseases in India and is of significant economic importance in recent years. No commercial soybean cultivar is reported to be resistant to this disease. In the current study, twenty-six advanced breeding lines were evaluated under epiphytotic field conditions, and thirty-four genotypes, including advanced breeding lines, commercial cultivars, and germplasm lines, were evaluated for resistance to S. rolfsii under controlled glasshouse conditions. Most of the genotypes were found susceptible to S. rolfsii; however, PS 16-70, PS 16-61, NRC 137, NRC SL-1, JS 20-34, NRC 7, and AGS 25 showed moderate resistance reaction to S. rolfsii. Furthermore, agronomic traits were evaluated after inoculating S. rolfsii in the glass house study. Area under disease progress curve (AUDPC) was positively correlated with root-and-shoot polyphenol oxidase and negatively correlated with root-and-shoot phenols and peroxidase. Moderate resistance cultivars were further evaluated for initiation of defense reaction against S. rolfsii. All the genotypes produced substantial defense enzymes and compounds after inoculation. Principal component analysis showed that the moderate resistance genotype PS 16-70 was positively associated with root and biochemical traits. In contrast, other moderate resistant genotypes showed a positive association with shoot traits. These moderately resistant genotypes could be used in breeding programs to develop high-yielding and collar rot-resistant varieties and mapping populations to map genes/quantitative trait loci (QTL) governing resistance.