Biochemical Basis and Mechanism of Wilt (Fusarium udum) Resistance in Pigeonpea

Resistant genotypes had higher peroxidase (PO) activity in root as well as leaf than susceptible genotypes under uninoculated conditions. The activity of polyphenol oxidase (PPO) increased in root of resistant plants on inoculation. The healthy (uninoculated) plants showed higher activity of phenylalanine ammonia lyase (PAL) in root as well as leaf as compared to infected (inoculated) plants. The activity of PAL increased in root as well as leaf at later stages of inoculation. Total phenols reduced drastically in roots of susceptible genotypes at later stages of inoculation. Higher total phenols were produced in leaf of resistant genotypes at later stages of inoculation. Inoculation caused an increase in the acid detergent fibre (ADF) and lignin of root of resistant as well as susceptible genotypes. This indicates the polymerization of cinnamyl alcohol into ADF and lignin, which causes thickening of cell wall in roots of plant responsible to check the penetration of fungus through root.