AUTHOR=Talukder Zahirul I. , Ma Guojia , Hulke Brent S. , Jan Chao-Chien , Qi Lili 

TITLE=Linkage Mapping and Genome-Wide Association Studies of the Rf Gene Cluster in Sunflower (Helianthus annuus L.) and Their Distribution in World Sunflower Collections

JOURNAL=Frontiers in Genetics

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2019.00216

DOI=10.3389/fgene.2019.00216

ISSN=1664-8021

ABSTRACT=<p>Commercial hybrid seed production in sunflower currently relies on a single cytoplasmic male sterility (CMS) source, PET1 and the major fertility restoration gene, <italic>Rf1</italic>, leaving the crop highly vulnerable to issues with genetic bottlenecks. Therefore, having multiple CMS/<italic>Rf</italic> systems is important for sustainable sunflower production. Here, we report the identification of a new fertility restoration gene, <italic>Rf7</italic>, which is tightly linked to a new downy mildew (DM) resistance gene, <italic>Pl<sub>34</sub></italic>, in the USDA sunflower inbred line, RHA 428. The <italic>Rf7</italic> gene was genetically mapped to an interval of 0.6 cM on the lower end of linkage group (LG) 13, while <italic>Pl<sub>34</sub></italic> was mapped 2.1 cM proximal to the <italic>Rf7</italic>. Both the genes are located in a cluster of <italic>Rf</italic> and <italic>Pl</italic> genes. To gain further insights into the distribution of <italic>Rf</italic> genes in the sunflower breeding lines, we used a genome-wide association study (GWAS) approach to identify markers associated with the fertility restoration trait in a panel of 333 sunflower lines genotyped with 8,723 single nucleotide polymorphism (SNP) markers. Twenty-four SNP markers on the lower end of LG13 spanning a genomic region of 2.47 cM were significantly associated with the trait. The significant markers were surveyed in a world collection panel of 548 sunflower lines and validated to be associated with the <italic>Rf1</italic> gene. The SNP haplotypes for the <italic>Rf1</italic> gene are different from <italic>Rf5</italic> and the <italic>Rf7</italic>gene located in the <italic>Rf</italic> gene cluster on LG13. The SNP and SSR markers tightly flanking the <italic>Rf7</italic> gene and the <italic>Pl<sub>34</sub></italic> gene would benefit the sunflower breeders in facilitating marker assisted selection (MAS) of <italic>Rf</italic> and <italic>Pl</italic> genes.</p>