USE OF SEEDLING PROGENY TESTS FOR GENETIC-STUDIES AS PART OF A POTATO(SOLANUM-TUBEROSUM SUBSP TUBEROSUM) BREEDING PROGRAM

A diallel set of crosses, including selfs and some reciprocal crosses, was made between 15 parents chosen for their male fertility from thos e included in a tetraploid potato (Solanum tuberosum subsp. tuberosum) breeding programme at the Scottish Crop Research Institute. Seedling progeny tests were used to evaluate the progenies for non-race-specifi c resistance to late blight (Phytophthora infestans) in both foliage a nd tubers, quantitative resistance to the white potato cystnematode (P CN) (Globodera pallida) and the commercial worth of their tubers as ju dged by breeders' visual preference. No reciprocal differences were fo und. Comparisons of the selfs and crosses revealed inbreeding depressi on for breeders' preference, which varied among the parents from negli gible to severe, whilst there were also statistically significant diff erences for foliage and tuber blight, but not for PCN. When the selfs were omitted from the combining ability analyses, large differences in general combining ability (GCA) were found for all four traits, and s maller differences in specific combining ability for tuber blight and breeders' preference. The only statistically significant correlation b etween GCAs for different traits was a favourable one of r = 0.56 betw een foliage and tuber resistance to late blight. It was concluded that prospects were good for simultaneously improving all four traits by m ultitrait genotypic recurrent selection.