Facilitation of introgressive hybridization of wild polyploid mexican potato species using DNA markers of R genes and of different cytoplasmic types

Nowadays potato breeding is targeting to develop genetically divers high yielding varieties with multiple pathogen resistance traits. Interspecific hybridization jointed with marker-assistant-selection (MAS) can effectively combine the R genes from different resistance sources. Additionally to effective pyramiding the target genes, MAS allows to restrict introgression of genetic factors conferring the undesirable traits, for example, male sterility of interspecific hybrids associated with Solanum stoloniferum -derived W/gamma cytoplasm that complicate the traditional breeding. Current study is targeting to search for the opportunities to improve the efficiency of introgressive hybridization between common potato and Mexican polyploid species Solanum. neoantipoviczii (= S. stoloniferum ) and S. guerreroense using MAS with DNA markers for different cytoplasmic types and markers associated with major R -genes to the most harmful potato pathogens. DNA-based markers of genes for late blight resistance ( R2 like, R3a, Rpi-blb1, Rpi-sto1 ), for extreme resistance to Potato virus Y (PVY) ( Ryadg, Rysto, Ry-fsto ) and for H1 gene for resistance to the root cyst nematode ( Globodera rostochiensis, pathotype Ro1) were used in this study. Based on the MAS, hybrid genotypes with different combinations of these markers were selected. Among them, there were the clones with high field resistance to late blight and to PVY. Of 29 hybrid clones from different combinations of crossing with polyploid Mexican species used as the maternal forms, 15 had a W/g cytoplasmic type and were male sterile; both these traits were maternally inherited. The remaining hybrids with W/a cytoplasm produced fertile pollen and were used in interspecific crosses as pollinators. Selection of resistant clones with W/alpha cytoplasm and elimination of genotypes with sterile W/g cytoplasm among wild species germplasm could increase the probability of obtaining male fertile introgressive lines. This approach allows to obtain the multi-species hybrid genotypes that combine R genes for resistance to pathogens from different Mexican species and to avoid various types of male sterility in breeding. The joint use of two systems of DNA markers, i.e. nuclear markers associated to R genes, and cytoplasmic markers for male sterility factors, could reduce costs and increase efficiency of target gene pyramiding programs.