Use of tuber progeny tests for genetical studies as part of a potato (Solanum tuberosum subsp. tuberosum) breeding programme

A diallel set of crosses, including selfs and some reciprocal crosses, was made between 15 parents, chosen for their fertility, from those included in a tetraploid potato (Solanum tuberosum subsp. tuberosum) breeding programme at the Scottish Crop Research Institute. The progenies were grown in randomised complete block trials with two replicates at a high-grade seed site from 1994 to 1996 inclusive and at a ware site in 1995 and 1996. The parents were included in the ware trials. Tubers were assessed for visual preference in all trials and for fry colour at both sites in 1996. Emergence and maturity were recorded in the ware trials and the tubers were assessed for yield, dry matter, size, appearance (regularity of shape), scab, uniformity, sprouting in store and keeping quality. There were very few growth cracks and very few internal defects. No reciprocal differences were found. Inbreeding depression was marked for emergence, yield, tuber size and appearance, and visual preference. In contrast, the selfs had a lighter fry colour than the parents and F^sub 1^s. Combining-ability analysis (selfs omitted) identified fry colour, emergence, maturity, yield, dry matter and sprouting resistance as traits for which the GCA (general combining ability) variance and narrow-sense heritability were high enough for good progress from full-sib family selection. Correlations between GCAs for pairs of traits were examined, including those from previously published seedling progeny tests. For fry colour, an unfavourable correlation with low yield (r = 0.596) was compensated by a favourable one with high dry matter content (r = 0.652), whereas unfavourable ones between foliage and tuber blight resistance and sprouting susceptibility (r = 0.578 and 0.596) were identified for monitoring. Clones with high GCAs were identified for use as parents in future breeding and the extent to which GCAs could be predicted from the parents, and the offspring means from the midparent means, was determined by regression and correlation analysis. The offspring-midparent regression was highest for fry colour, followed by dry matter, emergence and sprouting. Values were lower for scab due to environmental variation; for maturity, yield and tuber size due to SCA (specific combining ability); and for visual preference due to both factors. The implications for a breeding strategy are discussed.[PUBLICATION ABSTRACT]