A Recombination Suppressed Region of Sunflower (<i>Helianthus annuus</i> L.) Linkage Group 13 Covers Restoration of Fertility (<i>Rf1</i>) and Downy Mildew Resistance (<i>Pl</i>) Gene Clusters

Abstract

A number of genes that control valuable for breeding traits introgressed from wild relatives, i.e. pollen fertility restoration, resistance to fungal diseases (downy mildew and rust), are mapped on linkage group 13 of the cultivated sunflower Helianthus annuus L. genome. In sunflower and other plants, the recombination in the chromosome regions containing resistance genes can be suppressed that is favourable for marker assisted selection with applying molecular markers linked to these loci. The joint inheritance of the loci Rf1 (the phenotypic marker is fertility restoration trait) and Pl5/Pl8 conferring resistance to many races of Plasmopara halstedii (Farl) Berl. De Toni (the STS marker Ha-P1) was studied in the F2 generation of hybrids between a sterile line VIR 116A lines and pollen fertility restorers from sunflower VIR collection. In the crossing VIR 116А × VIR 740, the frequency of recombination between the loci Pl5Pl8 and Rf1 constituted 8.61 whereas in the crosses VIR 116А × VIR 195 and VIR 116А × VIR 80 turned out to be twice as high. In all examined F2 populations the absence of phenotypic class of sterile plants possessing paternal Нa-Р1 marker variant was mentioned. It has been shown by the cytological analysis that pollen fertility indices are most probably determined by the plant genotype rather than the male gametophyte allelic constitution. A deficiency of a recombinant F2 class was proposed to be associated with embryonic lethality, i.e. the collapse of zygotes carrying the recessive allele of fertility restoration gene and a specific allele of the resistance (susceptibility) gene obtained from the male parent.