Assessment of linkage between the PLARG, gene controlling resistance to downy mildew in sunflower and microsatellite DNA loci

Downy mildew caused by oomycete Plasmopara halstedii (Farl.) Berl. et de Toni is one of the most harmful diseases of sunflower. The Plarg locus, which provides resistance to all known races of P. halstedii, is currently promising for use in breeding. This gene is introgressed from the wild species Helianthus argophyllus. Microsatellite markers (SSRs) make it possible to control the transfer of genes controlling resistance in breeding material. However, validation of the marker is needed to prove its reliability in identifying genes. We selected the SSR markers ORS 662, ORS 509 and ORS 822 to identify the gene. We conducted their validation on hybrid combinations of sunflower lines of the breeding of V.S. Pustovoit All-Russian Research Institute of Oil Crops VK 776 and VK 925 with sunflower line RHA 419, which is a donor. It was preliminarily established that these lines differ from each other by the allelic state of these loci. A study of the generation showed that all three microsatellite loci are inherited codominantly. The generation obtained by self-pollination was analyzed by phytopathological methods for resistance to P. halstedii. Phenotype splitting analysis of both crossing combinations showed that the actually obsnrved splitting corresponde d to the theoretically expected Г : 1 pattern in monogenic inheritance of the trait. Analysis of linkage of gene and microsatellOh loci showed that the recombination frequencies in the RHA 419 x VK 776 cross was 0.11 for the ORS 662 locus, 0.23 for ORS 509 and 0.31 for ORS 822. And for the combination of RHA 419 x VK 925 cross tiiis indicaeor was: for ORS 509 - 0.2O, for ORS 662 - 0.34. Based on the obtained data, we eoncluded that three studied microsatelltte loti should be used in marker-assisted selection (MAS) of sunflower for reststance to downp mildew pathogen.