|LIU, ZHAO - North Dakota State University
|LONG, YUNMING - North Dakota State University
Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2018
Publication Date: 2/13/2019
Citation: Liu, Z., Long, Y., Xu, S.S., Seiler, G.J., Jan, C.C. 2019. Unique fertility restoration suppressor genes for male-sterile CMS ANN2 and CMS ANN3 cytoplasms in sunflower (Helianthus annuus L.). Molecular Breeding. 39:22. https://doi.org/10.1007/s11032-018-0922-y.
Interpretive Summary: A viable sunflower industry is dependent on the production of new and improved hybrids. The genetics of current sunflower hybrids are relatively narrow creating the need to expand its diversity. The breeding of sunflower as a hybrid crop requires male and female parents. Traditionally, crossing of the two are predictable, but occasionally one sees unexpected results where fertility is lost in the progenies. It has been speculated that silencing/suppression gene(s) are responsible for these abnormalities. The current study discovered the presence of silencing genes in certain hybrid combinations causing loss of fertility restoration. Molecular markers have been developed to identify these silencing genes and these markers will assist breeders in identifying breeding lines with or without the silencing gene(s). Thus, fertility restoration silencing gene(s) need to be considered in a breeding program when new female cytoplasm sources and fertility restoration lines are developed.
Technical Abstract: Single dominant fertility restoration (Rf) genes for cytoplasmic male-sterile lines CMS ANN2 and CMS ANN3 were previously identified in three and five sources, respectively. However, the expression of the dominant Rf genes were suppressed when crossing restoration lines with three inbred lines. Preliminary results indicated that the segregation of the fertility in most testcross progeny families from crosses of the half-diallel F1’s of restoration lines with the two CMS lines, respectively, did not agree with those of the F2 generation of the half-diallel crosses. In this study, using selected CMS ANN2 and CMS ANN3 plants without the silencing suppressor (S) genes, we clarified the conflicting results between the segregation of corresponding testcrosses and the F2’s, confirming the existence of S genes in CMS lines and the relationship among the Rf genes from different sources for the two CMS lines. Inheritance study suggested that Rf gene suppression was controlled by single dominant gene in specific backgrounds, whereas two to three S genes could exist in certain backgrounds. Using a testcross population Rf ANN2-P21/RHA 274//Rf ANN2-P21, a single S gene from RHA 274, designated S1, was mapped to a recombination suppressed region on the sunflower linkage group (LG) 3, co-segregating with 16 SSR or PCR-based single-nucleotide polymorphism (SNP) markers, flanked by NSA_003339 and ORS124 at a distance of 1.4 and 0.7 cM, respectively. These molecular markers will potentially assist in identifying lines without suppressor genes, including CMS lines. The mechanisms of Rf gene suppression are also discussed.