Lipoxygenase metabolites of alpha-linolenic acid in the development of resistance in pigeonpea, Cajanus cajan (L.) Millsp, seedlings against Fusariumudum infection

Lipoxygenase (LOX) activity was measured in germinating pigeonpea Cajanus c ajan seedlings, resistant (ICP-8863) and susceptible (ICP-2376) to wilt fun gus, before and after infection with Fusarium udum. LOX activity was signif icantly higher in the resistant than in the susceptible cultivars of pigeon pea and was enhanced further in response to infection with Fusarium udum. T his increase in LOX activity in the resistant cultivars of pigeonpea appear s to be due to the induction of lipoxygenase isozymes in response to infect ion. Analysis of the endogenous LOX metabolites in pigeonpea seedlings reve aled the predominant formation of 13-hydroperoxyoctadecadienoic acid (13-HP ODE) in healthy seedlings and 13-hydroperoxyoctadecatrienoic acid (13-HPOTr E) in infected seedlings. Further studies on the effects of LOX metabolites on the growth and multiplication of Fusarium udum showed that HPOTrEs, LOX metabolites of alpha -linolenic acid, are more anti-fungal compared to HPO DEs, LOX metabolites of linoleic acid.