A quantitative genetic study of Sclerotinia head rot resistance introgressed from the wild perennial Helianthus maximiliani into cultivated sunflower (Helianthus annuus L.)

Authors: Talukder, Md Zahirul; Underwood, William; MISAR, CHRISTOPHER - Former ARS Employee; Seiler, Gerald; Cai, Xiwen; LI, XUEHUI - North Dakota State University; Qi, Lili

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2022
Publication Date: 7/13/2022
Citation: Talukder, M.I., Underwood, W., Misar, C., Seiler, G.J., Cai, X., Li, X., Qi, L. 2022. A quantitative genetic study of Sclerotinia head rot resistance introgressed from the wild perennial Helianthus maximiliani into cultivated sunflower (Helianthus annuus L.). International Journal of Molecular Sciences. 23(14). https://doi.org/10.3390/ijms23147727.
DOI: https://doi.org/10.3390/ijms23147727

Interpretive Summary: Sclerotinia head rot (HR) is a serious disease of sunflower caused by the fungus Sclerotinia sclerotiorum. It is most damaging in the cool humid Northern Great Plains regions of the United States where most of the sunflower is grown. Sunflower growers frequently suffer serious economic loss by reduced seed yield, as well as by degraded oil and seed quality. Highly resistant germplasms have been developed through introgression of HR resistance genes from the wild perennial sunflower species, Helianthus maximiliani. Molecular characterization of HR resistant germplasms is vital for successful utilization of HR resistance in a marker-assisted selection (MAS) breeding program. A mapping population was developed by crossing a HR resistant germplasm, HR21 with a HR susceptible sunflower inbred line, HA 234. The mapping population was evaluated in field trials in North Dakota and Minnesota during the summers of 2019-2020 to identify genetic loci contributing HR resistance. A total of 16 loci were identified for HR resistance. Tightly linked molecular markers flanking the identified HR resistant loci will facilitate MAS breeding to combat the disease in sunflower.

Technical Abstract: Sclerotinia head rot (HR), caused by Sclerotinia sclerotiorum, is an economically important disease of sunflower with known detrimental effects on yield and quality in humid climates worldwide. The objective of this study was to gain insight into the genetic architecture of HR resistance from a sunflower line HR21 harboring HR resistance introgressed from the wild perennial Helianthus maximiliani. An F2 population derived from the cross of HA 234 (susceptible-line)/HR21 (resistant-line) was evaluated for HR resistance at two locations during 2019-2020. Highly significant genetic variations (p <0.001) were observed for HR disease incidence (DI) and disease severity (DS) in both individual and combined analyses. Broad sense heritability (H2) estimates across environments for DI and DS were 0.51 and 0.62, respectively. A high-density genetic map of 1,420.287 cM was constructed with 6,315 SNP/InDel markers developed using genotype-by-sequencing technology. A total of 16 genomic regions on eight sunflower chromosomes, 1, 2, 10, 12, 13, 14, 16 and 17 were associated with HR resistance, each explaining between 3.97 to 16.67% of the phenotypic variance for HR resistance. Eleven of these QTL had resistance alleles from the HR21 parent. Molecular markers flanking the QTL will facilitate marker-assisted selection breeding for HR resistance in sunflower.