Analyses of genomic regions linked with resistance to basal stem rot in sunflower (Helianthus annuus L.) under field conditions

Sunflower (Helianthus annuus L.) is one of the four important sources of edible oil in the world. Fungal diseases are considered as major constraints for its seed yield and quality. Basal stem rot resulted by Sclerotinia sclerotiorum (Lib.) de Bary fungus, is known as a serious disease on oily sunflower, worldwide. In this project, genomic region linked with partial resistance to basal stem rot disease was identified using a population of recombinant inbred lines (RILs) created from the hybridization between PAC2 (♀) and RHA266 (♂) lines. Nine phenotypic characters related to disease resistance including PN4D, PN8D, PN12D, NCW100S, CW100S, NCPY, CPY, DP100S and DPY were measured under artificial infection in the field conditions. Newly developed genetic linkage map of sunflower was used for detecting and mapping QTLs. The linkage map includes 210 SSR and 11 SNP markers distributed in 17 groups. The analysis was carried out using composite interval mapping (CIM) procedure. High coefficient of variation (CV) was detected for those studied characters that reveal high genetic variability for susceptibility to disease in the studied sunflower RIL population. Totally, 56 putative QTLs were identified for the studied nine quantitative characters. The number of QTLs for each character ranged from 1 to 9, explaining 0.91 to 80.75% of phenotypic variation (R2). Additive effect sign was positive for 17 QTLs, suggesting that the promising allele has been transmitted from male parent (RHA266). In this project, major QTLs (LOD≥2.5 and R2≥10%) were identified for all of the studied characters, exceptifor NCW100S and CW100S characters. The major QTLs are important for running marker-aided selection (MAS) in resistant breeding programs.