Improving the yield, processing quality and disease and pest resistance of potatoes by genotypic recurrent selection

Abstract

A potato (Solanum tuberosum Gp Tuberosum) breeding programme is described and analysed in which resistances to late blight [Phytophthora infestans (Mont.) de Bary] and the white potato cyst nematode (Globodera pallida) have been combined with a modest increase in yield and acceptable fry colour for processing. It began in 1991 and has involved cycles of crossing, selection between from 120 to 145 progenies (full-sib families), and clonal selection within the selected progenies. We have shown that the breeding scheme can operate on a 3-year cycle with limited within progeny selection, and on a 5- or 6-year cycle with more extensive within progeny selection. Six years are required when resistance to late blight is assessed in the tubers as well as the foliage. The more extensive within progeny selection is recommended once genes have been combined from sufficient parents to achieve one’s objectives. The yield increase after three cycles of indirect selection through breeders’ visual preference was only modest because it was operating against a decrease which would occur in the absence of selection. A practical improvement in the scheme would be to increase the number of progenies assessed to over 200, given the moderate to high heritabilities of the progeny and clonal tests. But this would require a considerable effort because the success rate achieved with the potato pollinations was typical at just over 30%. In the fourth cycle we showed how new breeding objectives and germplasm could be accommodated whilst continuing to maintain progress, something that is important in any long term breeding strategy.