Marker-assisted selection of diploid and tetraploid potatoes carryingRpi-phu1, a major gene for resistance toPhytophthora infestans

TheRpi-phu1 gene originates from an interspecific hybrid betweenSolanum stenotomum andS. phureja, and confers a high level of resistance toPhytophthora infestans (late blight) in potato. TheRpi-phu1 was introduced by crossing at the diploid level into theS. tuberosum gene pool and then transferred to the tetraploid level by means of2n gametes. Tetraploid lines carrying theRpi-phu1 were selected for further crosses. A molecular marker GP94, linked in mapping population 97-30 with theRpi-phu1 (6.4 cM), was applied to other unselected populations (2 diploid and 1 tetraploid), and was shown to be useful in marker-assisted selection (MAS) of the resistant individuals. GP94 was applied also in commercial breeding in 2 tetraploid populations. Although the marker allele of GP94, characteristic for theRpi-phu1 presence, was rare in theS. tuberosum gene pool, it seemed to be common in 2 other sources of resistance to late blight:S. ruizceballosii andS. kurtzianum.