Changes in Phenylpropanoid Pathway during Compatible and Incompatible Interaction of Ricinus communis-Fusarium oxysporum f.sp. ricini

The plant pathogen interaction was studied in relation to phenylpropanoid pathway at biochemical level in the resistant and susceptible genotypes of castor at 0 h after infection (h.a.i), 24, 48 and 72 h.a.i, respectively, in wilt pathogen infected and non-infected genotypes. The phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), Cinnamate 4-hydroxylase (C4H), p-Coumaric acid-3-hydroxylase (C3H) activities were studied in both resistant and susceptible varieties. Higher activities of these enzymes were noted in resistant genotypes at interval of 24 h.a.i for PAL, 48 h.a.i. for PPO and C4H while 0 h.a.i for C3H. The presence of one constitutive isoform and an induced isoform was noted for PPO. Isoform PPO-2 was absent in infected and non-infected susceptible genotypes at 48 h.a.i. Thus, overall results indicated the involvement of several of the phenolics and quinones in the processes of resistance.