ASSESSING GENERAL COMBINING ABILITY FOR GANGRENE RESISTANCE BY MEANS OF A GLASSHOUSE SEEDLING TEST

A seedling progeny test for resistance to gangrene (Phoma foveata) was used to evaluate progenies from a 15 x 15 half diallel set of crosses , including 14 selfs and 25 reciprocal crosses, which was originally m ade to investigate the inheritance of resistance to late blight and cy st nematodes. Nine out of the 14 selfs were more susceptible than the crosses involving their parents, so that overall the selfs were slight ly more susceptible than the crosses, thus providing evidence of non-a dditive gene action in favour of resistance. However. when the seifs w ere omitted from the analysis, all of the variation between progenies could be attributed to differences in the General Combining Abilities (GCAs) of their parents. The four parents with the best GCAs for gangr ene resistance all had sizeable contributions from Solanum tuberosum s ubsp. andigena in their pedigrees.