Early-generation selection between and within pair crosses in a potato (Solanum tuberosom subsp. tuberosum) breeding programme

In 1992, 72 seedlings from each of 198 pair crosses were grown in a glassho use, and the tubers produced by each plant were visually assessed on a 1-9 scale of increasing preference. Three groups of four progenies with high, m edium and low mean scores were chosen to progress, without selection via tu ber progenies and four-plant plots at a high-grade seed site, to replicated yield trials in the third clonal generation. The three groups maintained t heir high, medium and low scores for visual preference over the three clona l generations and also had high, medium and low scores in the second and th ird clonal generations for yield, size and appearance of tubers, all of whi ch were components of visual preference. The three groups were predicted to have 13.6%, 1.8% and 0.2% of their clones exceeding the mean of 13 control cultivars for visual preference in the replicated trials, and 12.1%, 4.9% and 1.4% for yield, and 56.8%, 37.1% and 14.8% for appearance. The experime nt confirmed that selection for visual preference within crosses in the see dling and first clonal generations is very ineffective, but that worthwhile progress can be made from selection in the second clonal generation, with correlated responses for faster emergence, earlier maturity, higher yield a nd greater regularity of shape (appearance). Combining selection of the hig h group of progenies with selection in the second clonal generation of the best 34 out of the 120 clones in this group, produced a response in visual preference in the third clonal generation of 1.00 compared with a maximum p ossible of 1.74. Ways of achieving further improvements in early-generation selection are discussed.