Enzymatic response of olive varieties to parasitism by Xiphinema index (Nematoda: Longidoridae).

Phenols content, phenylalanine ammonia lyase (PAL) and peroxidase (POD) activities were determined in leaves and roots of one cultivar (FS-17) and one rootstock (DA-12I) of olive (Olea europaea L.), uninfected and infected by different population densities of Xiphinema index 6 months after inoculation. The role of phenols and peroxidase in the response of olive to feeding by nematodes was confirmed by the experiment. Phenols content and PAL activity were higher in uninfected roots of DA-12I, whereas phenols increased and PAL decreased in the roots of both varieties in relation to the nematode inoculum density. The variation of phenols qualitative profile in the roots of DA-12I suggested a translocation of oleuropein from the leaves to the roots in response to X. index feeding. POD activity increased in roots and leaves of DA-12I, but only in the leaves of FS-17. Analysis of kinetic parameters showed that the same POD isozyme is present in both varieties.