CORRELATION BETWEEN RESISTANCE TO LATE BLIGHT IN FOLIAGE AND TUBERS IN POTATO CLONES FROM PARENTS OF CONTRASTING RESISTANCE

The relationship between resistance to late blight in foliage and tube r was examined on 50 clones of each of five progenies from crosses whe re one parent was resistant in both foliage and tuber and the other su sceptible. Foliage resistance was assessed in a held trial and tuber r esistance in a laboratory test on glasshouse-grown tubers. The genetic al and environmental components of variance and the phenotypic and gen etical correlations between foliage and tuber blight scores were deter mined for each progeny. Foliage and tuber resistance were correlated, indicating either that both are determined by the same genes or by dif ferent linked genes. The environmental component of variation was grea ter for tuber blight than foliage blight. We suggest that the most eff ective way of selecting for resistance to both aspects of the disease in a breeding programme is to select those resistant in the foliage an d then screen them for tuber resistance.