Alteration of Metabolites and Polyphenol Oxidase Activity in Wilt Resistant and Susceptible Pigeonpea Genotypes during Fusarium udum Infection

Biochemical variations were studied in wilt (Fusarium udum) resistant (ICPL 87119, ICP 8863 & Vaishali) and susceptible (ICP 2376 & T_15–15) genotypes of pigeonpea at 0 day after infection (DAI), 5 DAI and 10 DAI in infected and non-infected tissues. Our results indicated that total soluble sugar reduction was more pronounced in infected leaves and roots of susceptible genotypes at 10 DAI. Phenol content increased at 5 DAI but later decreased at 10 DAI. The infected leaves of resistant genotypes accumulated 50–52% higher phenol content than the non-infected leaves while the infected leaves of susceptible genotypes had 36–45% higher phenol content than the non-infected leaves. The free amino acid content was significantly increased in infected leaves of susceptible genotypes compared to resistant ones. The enhancement in polyphenol oxidase (PPO) activities were more in infected resistant genotypes than the infected susceptible genotypes at 5 DAI but later it declined in all the genotypes. The expression of PPO-2 isozyme in resistant genotypes after infection further confirmed higher activities of PPO at 5DAI. These results reveal that higher phenol content and PPO activities in resistant genotypes may restrict the disease after infection.