Mechanism of resistance in cowpea to the root-knot nematode, Meloidogyne incognita Race 1: I early induction of phenylalanine ammonia lyase (E.C. 4.3.1.5.) and chlorogenic acid Sirohi Anil, Dasgupta D.R. Division of Nematobgy, Indian Agricultural Research Institute, New Delhi-110 012. Abstract The major goal of the investigation was to provide evidence for early induction of phenylalanine ammonia lyase (PAL, E.C. 4.3.1.5.), the first key enzyme of the phenylpropanoid pathway, and to examine it's relationship with resistance expression in cowpea cultivar C-152 inoculated with root-knot nematode, Meloidogyne incognita race I. The rate of increase of PAL and it's activity between 24–72 hours was ostensively higher in inoculated resistant cowpea cultivar C-152 in contrast to it's control as well as to inoculated and uninoculated susceptible cowpea cultivar Pusa do Fasli (PDF), connoting that the nematode-mediated biomolecular defense mechanism was activated as early as 24 hours after inoculation in resistant cowpea cultivar. It was inveterately demonstrated that chlorogenic acid (CGA) turnover values were higher in between 24–72 hours in inoculated resistant cultivar C-152 compared to inoculated susceptible cultivar PDF, implying that the onset of faster rate of PAL in inoculated resistant C-152 preceded highest concentration of CGA which was not the case in PDF, indicating an early, faster onset or completion of lignification in C-152 as compared to PDF. Analogously there were elevated levels of RNase and proteins in the inoculated cowpea cultivar C-152 than in the cultivar PDF. Top Key words Meloidogyne incognita, Phenylalanine ammonia lyase (PAL), Chlorogenic acid, Cowpea, Resistance, Phenylpropanoid pathway, Ribonuclease, protein. Top |