A BASIC PEROXIDASE ISOENZYME, MARKER OF RESISTANCE AGAINST PLASMOPARA-VITICOLA IN GRAPEVINES, IS INDUCED BY AN ELICITOR FROM TRICHODERMA-VIRIDE IN SUSCEPTIBLE GRAPEVINES

The constitutive expression of basic peroxidase isoenzymes in the Plas mopara viticola-resistant (Vitis vinifera x Vitis rupestris) x Vitis r iparia crossing and in the P. viticola-susceptible V. vinifera parent species was studied. The results illustrate that both leaves and stems of the (V. uinifera x V. rupestris) x V. riparia crossing showed the differential expression of a basic peroxidase isoenzyme B-3 (pI = 8.9) , this being almost completely absent from the P. viticola-susceptible V. vinifera parent species. To test whether the basic peroxidase isoe nzyme B-3 may be considered as a molecular marker of disease resistanc e in Vitis spp., suspension cell cultures derived from the P. viticola -susceptible V. vinifera parent species were treated with an elicitor (cellulase Onozuka R-10) from the soil fungus Trichoderma viride, a sp ecific and well-known elicitor of disease resistance reactions in grap evines. The results showed that treatment with the elicitor induces, s imultaneously with the activation of the disease resistance mechanism, the appearance of B-3 in the cell cultures. These results suggest tha t the basic peroxidase isoenzyme B-3 may be considered as a marker of disease resistance in Vitis species since it is present in the P. viti cola-resistant (V. vinifera x V. rupestris) x V. riparia hybrid and is induced by the elicitor Onozuka R-10 in cell cultures of the P. vitic ola-susceptible Vitis vinifera parent species. This conclusion is supp orted by the presence of this isoenzyme in other resistant and its abs ence in other susceptible Vitis spp.