Molecular markers as a tool in potato breeding for late blight resistance

Background. Resistance of potato сultivars to late blight caused by oomycete Phytophthora infestans (Mont.) de Bary is one of the priority areas of global and domestic potato breeding. To improve the breeding technology, the identification of DNA markers of resistance genes that are effective for the selection of valuable segregants in hybrid offspring is of particular relevance. Objectives. The aim of this study was to determine the diagnostic value of the Rpi-R1 , Rpi-R8 , Rpi-R3b , Rpi-blb1 , and Rpi-blb2 gene markers for the selection of valuable segregants in the progeny of interspecific hybrid clones from the VIR collection – sources of the late blight resistance trait. Material and methods . Two families of F 1 hybrids (156 individual plants), their parental clones 16/27-09, 171-3, 8-1-2004, Chilean potato cv. ‘Magelanes’, and potato cvs. ‘Alouette’, ‘Nayada’ and ‘Sudarynya’ were screened for the presence of five Rpi genes and tested in field trials for resistance to P . infestans. SCAR markers for Rpi genes were Rpi-R1-1205, Rpi-R3b-377, Rpi-R8-1276, Rpi-blb1-821, Rpi-sto1-890, and Rpi-blb2-976. Sequencing of PCR amplicons was used to verify the presence of Rpi-blb2-976 marker. Experimental data were analyzed by standard statistical methods like cluster analysis, analysis of variance (ANOVA), chi-square test (χ 2 test) and coefficient of association. Results. Cultivars and clones of interspecific potato hybrids – sources of late blight resistance, and F 1 hybrids from two types of crosses, differing in the reaction of parental forms to late blight (moderately resistant × resistant, and resistant × susceptible), were characterized for the target trait and the presence of SCAR gene markers. It was established that SCAR markers for the Rpi genes in parental forms of F 1 hybrids are in simplex condition, namely the SCAR marker for the Rpi-R1 gene in cv. ‘Magelanes’, that for Rpi-R8 and Rpi-R3b in hybrid 171-3, and the marker for Rpi-R1 , Rpi-R8 and Rpi-blb1 in clone 16/27-09. The F 1 progeny of 16/27-09 × 8-1-2004 hybrid (resistant × susceptible type cross) demonstrates a reliable relationship between late blight resistance and the presence of markers for Rpi-R8 and Rpi-blb1 genes (association coefficient r=0.24). The diagnostic value of markers for two genes ( Rpi-R8 and Rpi-blb1 ) is 85.4%.The F 1 progeny of ‘Magelanes’ × 171-3 hybrid (moderately resistant × resistant type cross) showed no association between late blight resistance and the presence of Rpi gene markers. Conclusions . Markers for Rpi-R8 and Rpi-blb1 genes can be used in potato breeding programs which use clone 16/27-09 as a source of late blight resistance.