THE EFFECT OF CULTIVAR MATURITY ON THE RESISTANCE OF POTATOES TO EARLY BLIGHT CAUSED BY ALTERNARIA-SOLANI

A series of clonal variants of common potato varieties which had been selected for different maturities were screened in the field for their resistance to early blight caused by the fungus Alternaría solani. Maturity of these cultivars was also rated in the field. A strong correlation was found between cultivar maturity and resistance to early blight. Earlier-maturing cultivars were more susceptible, and later-maturing cultivars were more resistant. Starch gel electrophoresis of the tuber enzymes of these cultivars indicated that the maturity variants did not differ with respect to the isozymes tested. This is consistent with the hypothesis that variants of the same cultivar, differing only in maturity, had been selected. These results therefore suggest that it may be difficult to select cultivars which are both early-maturing, and resistant to early blight. © 1990 Springer-Verlag.