Validation of microsatellite markers to identify Pl6, Pl8 and Plarg genes that control resistance to Plasmopara halstedii in sunflower

Downy mildew caused by the oomycete Plasmopara halstedii (Farl.) Berl. et de Toni is one of the most harmful sunflower diseases. Among the various measures to control it, the most economical is the development of resistant genotypes. At present, Pl6, Pl8, and Plarg loci are promising for use in breeding, providing resistance to all known P. halstedii races. Microsatellite markers (SSR) help to control the transfer of genes that control resistance in breeding material. However, validation of the marker is needed to prove its reliability in gene detection. There was studied the polymorphism of 9 microsatellite loci in 196 sunflower lines with different resistance to downy mildew. The ORS328 microsatellite locus was chosen as a marker of the Pl6 gene. Amplified fragment with 271 bp allows identifying genotypes resistant to the race 330. The lines that are the sources of the Pl8 gene did not differ from the others in the allelic composition of the ORS781 locus. Among the analyzed breeding samples, no polymorphism was revealed at this locus. To identify the Plarg gene, SSR markers ORS662 and ORS509 were selected. The analysis of 12 samples of the F2 generation from RHA-419 × I3BC2 (VK585 × VK195) crossing at these loci showed that both markers are inherited codominantly. The studied DNA markers can be used in marker-assisted selection (MAS) of sunflower for resistance to downy mildew pathogen.