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ACCUMULATION OF PHYTOALEXINS AND PHENYLALANINE AMMONIA LYASE IN CHICKPEA AFTER INOCULATION WITH ASCOCHYTA RABIEI AND THEIR ROLE IN DEFENCE MECHANISM

NIGHAT SARWAR, FARHAT F. JAMIL AND RIFFAT PARVEEN*

Abstract: The production of phytoalexins and phenylalanine ammonia-lyase (PAL) was measured in resistant and susceptible varieties of chickpea after inoculation with Ascochyta rabiei. The pterocarpan phytoalexins, medicarpin and maackiain were produced in chickpea plant tissues in response to inoculation. Maximum production of both the phytoalexins was obtained 24 hours after inoculation in resistant varieties, whereas it took five to nine days to reach its maximum in susceptible varieties. This accumulation was preceded by a transient rise in activity of PAL, the first enzyme in the biosynthetic pathway of phytoalexins. Maximum PAL activity was observed 12 to 24 hours after inoculation which coincided with the period of most rapid phytoalexin accumulation. These results suggested that rapid production of phytoalexins is the part of defence mechanism in chickpea and PAL has a regulatory role in the biosynthesis of these secondary metabolites.

Nuclear Institute for Agriculture & Biology (NIAB), P.O.Box 128, Faisalabad, Pakistan.
* Department of Chemistry, Bahauddin Zakariya University, Multan, Pakistan.