Combining ability analysis and correlation between breeding values in true potato seed

True potato seed (TPS) requires the selection of appropriate parents for developing hybrid offspring. Parents for routine crossing schemes need to be selected according to their combining ability. Hierarchical and factorial mating designs provide a mean values to assess the general combining ability (GCA) of clones included in crossing schemes. Furthermore, specific combining ability (SCA) may be investigated using the factorial mating design. The aim of this research was to determine the combining ability of clones included in early and intermediate TPS breeding populations developed by the Centro Internacional de la Papa (CIP). Likewise, correlations between breeding values (or additive genetic correlation, P-A) were calculated. Two hierarchical mating designs (in both the early and intermediate populations) and one factorial mating design (in the intermediate population) were evaluated in two contrasting Peruvian locations (La Molina - coastal desert, and San Ramon, warm humid tropics). Plant and tuber characteristics were recorded in these experiments. Significant GCA was observed for tuber yield in all experiments. The male's P-A between plant vigour after transplanting and tuber yield was significant, thereby suggesting that offspring with early vigorous growth are high yielding. Plant vigour was also correlated with tuber set, but only among the breeding value of female parents, which suggests that high tuber yield could be achieved because offspring with early, vigorous growth have many tubers. High tuber yielding hybrids can be obtained by choosing parents with significant GCA. whose tuber yield can also be further enhanced if the crosses have a significant SCA.