PROBLEMS OF CHESTNUT-GROWING IN GREECE SCREENING FOR RESISTANCE OF SEVERAL CHESTNUT PROVENANCES TO CRYPHONECTRIA (ENDOTHIA) PARASITICA (MURR.) ADERSON

The results show that all the Greek provenances were susceptible to the fungus. A high percentage of the inoculated trees died within 5 months after inoculation, and the rest in late spring early summer of the following year. The seedlings of C. mollissima and the hybrid were resistant, since they developed smaller cankers most of which were closed within 1 to 2 years.

Among the Greek provenances there was a small differentiation as regards their degree of susceptibility. The provenances of Lamia, Mitilini, Arnea and Karpenisi were less susceptible than the others, since they developed smaller cankers and also had a smaller percentage of dead trees within 5 months after inoculation.

A correlation was observed between the percentage of dead trees and the stem diameter at the point of inoculation and the mean canker length. Larger diameters and smaller mean canker length were related to a smaller proportion of dead trees.

The high percentage of dead trees in the short time of 5 months after inoculation is not due to a high susceptibility of the trees, but to the exceptional good conditions for the disease development and poor conditions for seedling development (age of trees, exceptional hot and dry year during disease development), which did not give any chance to the trees for resistant reaction.

These results show, that the resistant reaction in most of the naturally infected chestnut coppices by forming superficial cankers with callus tissue, is not genetic, but is due to the ontogenic predisposition for resistance of the trees during infection.

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