Effect of Fusarium udum infection on the activity of peroxidase, polyphenol oxidase and phenylalanine ammonia lyase in resistant and susceptible genotypes Pigeon pea

Pigeon pea (Cajanus cajan L.) is India's second most important pulse crop after chickpea. It is susceptible to several pathogens, including Fusarium udum, which is considered the most important fungal pathogen, causing considerable economic loss in India and worldwide. The present study aimed to evaluate the changes in pathogen-induced enzymes (PIE) in F. udum wilt-resistant (ICP-8863, BDN-1 and BDN-2) and susceptible genotypes (ICP-2376 and BAHAR) of pigeon pea after seven days of infection. Fifteen days old seedlings were inoculated with F. udum (10⁶ spores/ml) using the root-dip method. The wilt incidence was observed after seven days of infection; microscopic examination confirmed the presence of F. udum based on its characteristic mycelial pattern and conidial features. Biochemical response was recorded by estimating PIE viz., peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) in various pigeon pea genotypes after the manifestation of infection. The activity of PIE increased in resistant genotypes, particularly BDN-2, which showed the highest PO activity (1.57-fold), while BDN-1 recorded the highest PAL activity (1.55-fold). Overall, defense enzyme activity was lower in susceptible varieties. These results suggested that biochemical changes recorded in resistant genotypes help restrict the disease during infection.