GENOTYPE BY ENVIRONMENT INTERACTION FOR OIL QUALITY IN HIGH OLEIC ACID SUNFLOWER LINES

• Main Author: van der Merwe, Rouxléne
• Other Authors: Prof A Hugo
• Format: Others
• Language: en-uk
• Published: University of the Free State 2011
• Subjects: Plant Sciences
• Online Access: http://etd.uovs.ac.za//theses/available/etd-10172011-114113/restricted/

High oleic acid sunflower hybrids have been available on the market for a few years, but research on the stability of these genotypes for oil quality traits in South African production areas is limited. General aims of this study were to compare oil quality traits of high oleic sunflower against traditional sunflower genotypes in different environments, over seasons and under heat stress conditions and to identify possible genetic markers related to the oleic acid trait that would be useful in breeding programmes. Combined ANOVAs of oil, linoleic, oleic, palmitic and stearic acid content of 16 genotypes tested in a total of nine trials over eight locations and three seasons showed highly significant differences between genotype, environment and GXE. Significant GXE suggested differential response of genotypes across testing locations and years and the need for stability analyses. Stability analyses were performed for all oil traits using AMMI. Stability analyses indicated that high oleic genotypes 6 and 8 could be considered stable across environments and seasons for oil and oleic acid content and genotype 9 for palmitic and stearic acid content. Sunflower oil quality is affected by genotype and environmental conditions with temperature as a major influence. The effect of heat stress on seed yield and oil quality traits was investigated by applying a maximum temperature of 36ºC to plants during the critical seed-filling stage. This information was needed to define a breeding strategy to further improve seed oil quality in environments where heat stress may occur. All traits measured were significantly influenced by heat stress. The low heritability estimates observed for seed-related yield traits indicated that genetic improvement for these traits would be difficult. Oil and linoleic acid contents were significantly reduced by heat, while oleic acid content was significantly increased in traditional hybrids. The oleic acid content of the high oleic acid hybrid was unaffected, but this hybrid showed the largest decrease in oil content. High heritability estimates observed for oleic and linoleic acid content indicated that it is possible to genetically improve these traits under different temperature conditions. Since oleic acid content is influenced by the environment, this trait showed instability across environments. Genotypic selection for this trait using linked markers is independent from the environment. A segregating population comprising 78 F2 individuals was obtained from a cross between a high oleic acid and traditional sunflower line. AFLP and SSR markers were used to identify and map QTL, associated with the high oleic acid trait, putatively to LG 14 of the sunflower consensus map. A major QTL controlling the level of oleic acid was identified that explained 35% of the phenotypic variance for this trait. Markers linked to this trait were identified that could be useful in MAB. Physicochemical properties and oxidative stability of seed oil of high (82.6% oleic) and mid oleic acid (53.8% oleic) sunflower hybrids were compared with those of traditional sunflower (65.7% linoleic and 22.9% oleic). Oxidative stability was evaluated by measuring PV, p-AV and OSI values. High oleic acid oil had the best oxidative stability. Since oxidative stability was related to the unsaturation level of oil, the high oleic oil with significantly reduced linoleic acid content had the highest resistance to oxidation. Keeping quality of commercially available vegetable oils, including high oleic sunflower oil was evaluated using the Schaal oven test. Oil samples, placed in a heat cabinet at 63ºC were periodically examined for keeping quality by determining PV, p-AV and RI values. High oleic sunflower oil was twice as stable as traditional sunflower and canola oils.