Asian Research Journal of Agriculture

Bacterial blight is associated with physiological and biochemical changes in clusterbean, and differences among varieties may be reflected in oxidative-enzyme activity and biochemical constituents. This study compared four clusterbean varieties representing susceptible (RGC-986), moderately susceptible (RGM-112), moderately resistant (RGC-1017), and resistant (RGC-1066) reactions. Healthy and diseased leaves collected 40 days after sowing were analysed for polyphenol oxidase, peroxidase, catalase, chlorophyll, total phenolic compounds, total soluble, reducing and non-reducing sugars, soluble protein, and proline. Oxidative-enzyme activities generally increased in diseased leaves. The highest polyphenol oxidase activity in diseased leaves was recorded in RGM-112, the highest peroxidase activity in RGC-1017, and the highest catalase activity in RGC-986. Total chlorophyll declined after disease development, with the highest healthy-leaf value recorded in RGC-1017. Total phenolic content increased after infection and was highest in RGC-1066. Total, reducing, and non-reducing sugars decreased in diseased leaves, while RGC-1017 retained the highest total sugar content. Soluble protein also decreased following infection, with RGC-1066 showing the highest protein content in both healthy and diseased leaves. Proline increased in diseased leaves of all varieties and was highest in RGC-1066. Overall, the contrasting varietal responses were associated with differences in oxidative-enzyme activities and biochemical constituents, indicating that these traits accompany differential bacterial blight reactions in clusterbean.