Vol. 12, Issue 1 (2023)

Powdery mildew, caused by Leveillula taurica (Lev.) Arn., is a major crop disease of clusterbean in Karnataka and causes substantial economic losses. It reduces the effective photosynthetic leaf area, resulting in significant yield loss. Among the available management strategies, host plant resistance is the most suitable one. So, under greenhouse conditions, nine clusterbean genotypes were screened to identify resistant sources against the disease and understand the bio-chemicals conferring resistance. The role of biochemical parameters such as peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL) activities, total phenol (TP), and chlorophyll content in imparting resistance against powdery mildew in clusterbean was investigated to know the relationship of enzymes in the host with pathogen. None of the genotypes exhibited resistance to the powdery mildew pathogen. Moderately resistant varieties had higher enzymatic activities. Except for chlorophyll, all biochemical parameters increased significantly after inoculation in resistant varieties compared to susceptible varieties. Pathogen infection resulted in an increased PO, PPO and PAL activity, as well as higher phenol, which enhanced the mechanical strength of host cell wall and may also inhibit the fungus growth, as phenolics are fungitoxic in nature. The findings of the study indicate that the evaluated biochemical parameters could be used as reliable biochemical markers for early selection of powdery mildew resistant genotypes. The moderately resistant genotypes identified in this study could also be used as donor parents in breeding programs designed to improve powdery mildew disease resistance in clusterbean.