The application of DNA fingerprinting and marker–assisted backcross selection in breeding for sunflower high oleic acid content lines
Mokhele, Tshediso Andrew
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Sunflower (Helianthus annuus L.) high oleic acid content lines differ from conventional sunflower by an increase in oleic acid (C18:1) content of more than 60%. The current sunflower cultivars under production in South Africa are standard sunflower with high levels of linoleic acid (C18:2). The aim of this study was to improve the quality of oil produced by local sunflower germplasm with respect to oleic acid through employing a marker-assisted breeding technique to facilitate and speed up the recovery of the high oleic acid allele into the background of the recurrent parent genome. Eleven sunflower breeding genotypes with high and low oleic acid traits were obtained from the Agricultural Research Council-Grain Crops Institute (ARC-GCI) in Potchefstroom. The breeding genotypes were phenotypically characterised based on their oleic and linoleic acid levels using gas chromatography. Results demonstrated that the average mean of oleic and linoleic acid contents in high oleic acid genotypes were 72% and 17% respectively, while the average mean of oleic acid and linoleic acid contents in wild type lines were 33.5 % and 54 % respectively. These results indicated a perfect negative correlation between the amount of oleic and linoleic acids possessed in high and low oleic acid genotypes (R2 = -99.16%). Sequence characterised amplified region (SCAR) markers were tested to ascertain if any of the ten available dominant FAD2-1 markers was segregating with the high oleic acid allele. Four dominant SCAR markers (FAD2-1F4/R1; FAD2-1F4/R2; FAD2-1F13/R1; FAD2-1F14/R2) were strongly associated with the high oleic acid trait (P< 0.001). With regard to the inheritance of the high oleic acid trait, 143 plants of the F2 segregating population derived from a cross between the high oleic acid parent (AP901-95-3-4-1) and low oleic acid parent (H55-9-2-1-1) were genotyped with the four SCAR markers to determine the genetic state concerning the high oleic acid gene (Ol). Results from a Chi square analysis of the observed frequencies of each dominant FAD2-1 marker locus in 143 F2 individuals indicated that the deviation from the expected ratio of 3:1 (high to low oleic acid) was not statistically significant (P< 0.95) from the observed segregation ratio. These results were consistent with the previous finding that an incomplete dominant gene governs sunflower high oleic acid. A multiplex assay of 78 Simple sequence repeat (SSR) markers was optimised and evaluated on 143 plants of the F2 population to determine suitable SSR markers that can be used in a marker-assisted background selection. Only 14 markers were suitable for marker-assisted background selection based on their high polymorphic information content, allele frequency and maximum allele numbers. In conclusion, this study demonstrated the potential of using SSR and SCAR marker systems as a breeding tool to characterise and speed up the selection process in marker-assisted backcross breeding.