INDUCED TEMPORAL AND SPATIAL VARIATION IN HOST DEFENCE ENZYMES IN RESPONSE TO FUSARIUM WILT IN CHICKPEA

摘要

The present study evaluated the defense response of Chickpea wilt resistant and susceptible cultivars inoculated with pathogen Fusarium oxyporum f.sp. ciceri (Foc). Evaluation of pre-induced and pathogen-induced defense at 7 (S1), 15 (S2) and 30 (S3) days showed that the enzymatic activities differed not only within the root, stem and leaves but also between susceptible and resistant cultivars of chickpea and increased after inoculation with Foc. Peroxidase (PO) activity increased in all the tissues from S1 to S2 and declined thereafter. Conspicuous changes occurred at the rate of increase in activity of the enzyme between resistant and susceptible cultivars upon Foc inoculation over their corresponding control at the S2. Polyphenol oxidase (PPO) activity in resistant cultivars increased by 30% with over uninoculated control and induction was up to S3. The level of enzyme activity diminished from S2 to S3 and even fell below control levels in susceptible cultivars. Catalase (CAT) activity followed peroxidase trend however it was induced at S1 in Foc inoculated and at S2 in un-inoculated plants. Increase in CAT induction was significant in leaf tissues of infected plants and continued up to S3. Phenylalanine ammonia lyase (PAL) activity increased from S1 to S2 and thereafter it either slightly decreased or remained unchanged at S3. Foc inoculation elicited a sharp increase in PAL activity in the leaf and stem tissue of resistant cultivars. Foc inoculated induced β-1,3-glucanase and chitinase activity in the test cultivars. Maximum induction of chitinase was observed at S2 in roots of resistant cultivars whereas un-inoculated plants showed much less conspicuous changes. β-1,3-glucanase activity was high in stem tissues. Both control and challenged plants had higher levels of β-1,3-glucanase activity at S2 and S3, but the proportionate increase was much higher in resistant cultivars. The expression pattern of these defense enzymes reveals their use as established resistance markers and provides scope for manipulating their expression and development of wilt-resistant transgenic chickpea.