Refinement of Rf1-gene localization and development of the new molecular markers for fertility restoration in sunflower.

BACKGROUND: Ability to restore male fertility is important trait for sunflower breeding. The most commonly used fertility restoration gene in the production of sunflower hybrids is Rf1. The localization of Rf1 on the linkage group 13 has been previously shown, however, its exact position, its sequence and molecular mechanism for fertility restoration remain unknown. Therefore, several markers linked to Rf1 gene, commonly used for MAS, don't always allow to identify the genotype of plants. For this reason, the search for new markers and precise localization of the Rf1 gene is an urgent task. METHODS AND RESULTS: Based on previously identified single nucleotide polymorphisms (SNPs) at LG13, significantly associated with the ability to restore male fertility, two markers have been developed that have performed well after careful evaluation. These markers, together with other Rf1 markers, were applied for genotyping 72 diversity panel accessions and 291 individuals of F2 segregating population, obtained from crossing the cytoplasmic male sterility (CMS) AHO33 and restorer RT085HO lines. The analysis revealed no recombinants between Rf1 gene and SRF833 marker, the distance between Rf1 and SRF122 marker was 1.0 cM. CONCLUSIONS: Data obtained made it possible to specify the localization of the Rf1 gene and reduce the list of candidate genes to the 3 closely linked PPR-genes spanning a total of 59 Kb. However, it cannot be ruled out that analysis of the candidate region in the genome of fertility restorer lines can reveal new candidate genes in this locus that are absent in the cytoplasmic male sterility maintainer reference sequence.

Genotyping and lipid profiling of 601 cultivated sunflower lines reveals novel genetic determinants of oil fatty acid content.

BACKGROUND: Sunflower is an important oilseed crop domesticated in North America approximately 4000 years ago. During the last century, oil content in sunflower was under strong selection. Further improvement of oil properties achieved by modulating its fatty acid composition is one of the main directions in modern oilseed crop breeding. RESULTS: We searched for the genetic basis of fatty acid content variation by genotyping 601 inbred sunflower lines and assessing their lipid and fatty acid composition. Our genome-wide association analysis based on the genotypes for 15,483 SNPs and the concentrations of 23 fatty acids, including minor fatty acids, revealed significant genetic associations for eleven of them. Identified genomic regions included the loci involved in rare fatty acids variation on chromosomes 3 and 14, explaining up to 34.5% of the total variation of docosanoic acid (22:0) in sunflower oil. CONCLUSIONS: This is the first large scale implementation of high-throughput lipidomic profiling to sunflower germplasm characterization. This study contributes to the genetic characterization of Russian sunflower collections, which made a substantial contribution to the development of sunflower as the oilseed crop worldwide, and provides new insights into the genetic control of oil composition that can be implemented in future studies.

Nucleotide sequence polymorphism in the RFL-PPR genes of potato.

Cytoplasmic male sterility (CMS) is widely used for hybrid seed production in cultivated Solanaceae species. However, there is very limited information about CMS-Rf genetic systems in potato (Solanum tuberosum). Studying the CMS-Rf systems in potato is both of theoretical and practical significance due to the emergence of a new revolutionary strategy of reinventing potato as adiploid inbred line-based crop to develop F1 hybrid seed potato breeding (Lindhout et al. 2011; Jansky et al. 2016). To search for potato Rf gene candidates, the comparative genetic approach was applied. Based on similarity to petunia Rf-PPR592 gene, 38 fragments were identified in five loci of the whole-genome nucleotide sequence of the accession DM 1-3 516 R44 S. tuberosum Phureja group (https://blast.ncbi.nlm.nih.gov/Blast.cgi). The putative encoded mitochondrial proteins have 589-597 amino acid residues, similarto RF-PPR proteins of petunia and chili pepper and contain 14 or 15 PPR motifs. Primers have been developed flanking the most variable 782-865 bp regions of the selected loci, and polymorphism of the cloned fragments has been investigated in a subset of nine potato genotypes. The amplified fragments included seven or eight PPR motifs and lacked introns. The SNP frequencies ranged from 7.0 to 19.8% depending on the locus, while the ratio of nonsynonymous to synonymous substitutions varied between 0.9 and 2.1. Positions 1, 3 and 6 were the most variable in the studied PPR motifs. Our results demonstrated that the analysed sequences belong to the RFL-PPR gene subfamily and may be considered as Rf gene candidates in potato.