Morpho-biochemical responses of rice genotypes following feeding by the leaf folder, Cnaphalocrocis medinalis

Rice leaf folder, Cnaphalocrocis medinalis is a serious pest of rice and causes 30%–80% yield losses in epidemic outbreak resulting in 0.1–0.27 lakhs of rupees monetary losses per hectare in India. Insecticides are commonly employed to control this pest, but their use often escalates production costs and fosters pesticide resistance. Identifying insect-resistant rice genotypes and their resistance mechanisms is crucial for successful pest management. New sources of resistance providing long-lasting protection against leaf folder can be identified by studying the morphobiochemical characteristics of different rice genotypes. This study explored the role of various morphological traits of certain genotypes that confer resistance. Different biochemical constituents such as soluble protein, phenol, total soluble sugar and enzymes, namely peroxidase, polyphenol oxidase and catalase were assessed spectrophotometrically in all infested and uninfested genotypes and in standard resistant (TKM6) and susceptible (TN1) check genotypes. Leaf folder damage was negatively correlated with plant height and leaf length, while leaf width association was positively correlated. Among the different plant metabolites analysed, total soluble sugar and soluble protein showed positive correlation with leaf folder damage, conversely phenol and antioxidative enzymes showed negative correlation. When rice genotypes were exposed to leaf folder larval feeding, they exhibited defence responses characterized by reduction in the level of sugars and proteins, accumulation of phenolic compounds and upregulation of antioxidative enzymes. This study emphasized the significance of morphobiochemical characteristics in rice resistance mechanisms against leaf folder. By leveraging these traits, new resistant rice germplasms against leaf folder can be developed.