Breeding and genetic studies on vitamin E content in sunflower seeds

Póster presentado en la 18th International Sunflower Conference, celebrada en Mar de Plata y Balcarce (Argentina), del 27 de abril al 1 de marzo de 2012.

Tocopherols are natural antioxidants with vitamin E activity. They are synthesized exclusively in photosynthetic microorganisms and plants. Plant tissues vary enormously for total tocopherol content and composition, with the highest concentrations being found in seeds. The predominant tocopherol forms in seeds are gamma- and delta-tocopherol, which have only about one tenth the vitamin E activity of alpha-tocopherol, whereas the latter is the predominant form in photosynthetic tissues. Sunflower seeds are a notable exception as they primarily accumulate alpha-tocopherol, which makes sunflower seeds and oils one of the richest sources of dietary vitamin E. Nutritional studies have pointed to beneficial effects of moderate vitamin E supplementation on human health. Accordingly, sunflower seeds with naturally enhanced vitamin E content might be a promising alternative for producing healthier sunflower oils. The aim of this research was to select sunflower germplasm with increased vitamin E content, to study the inheritance of the trait, and to identify associated quantitative trait loci (QTL). A large germplasm collection of cultivated sunflower accessions was evaluated for seed vitamin E content using HPLC analysis with fluorescence detection. A line with increased seed vitamin E content was developed and the inheritance of the trait was studied through evaluation of the F1, F2, F3 and BC1 plant generations from crosses with a line with conventional seed vitamin E content. A genetic linkage map was also constructed using a set of 156 SSR and INDEL polymorphic and evenly spaced markers. QTL analysis was conducted using phenotypic data for vitamin E content in the F2 and F3 plant generations. Selection on the germplasm accessions with the highest vitamin E content allowed the isolation of an S4:5 line with an increased total tocopherol content, mainly in the alpha-tocopherol form (>95% of total tocopherols) of 467 mg kg-1 seed compared to 250.9 mg kg-1 seed in the line with conventional tocopherol content used as a control. Increased vitamin E content was also expressed in the pollen. Classical genetic studies revealed broad-sense heritabilities between 0.67 and 0.78 and narrow-sense heritabilities between 0.60 and 0.70. Additional estimates of heritability through parent-offspring correlation and realized heritability gave consistent values of 0.67 and 0.64, respectively. A major QTL on LG 10 was responsible for more than half of the explained phenotypic variation for increased tocopherol content, whereas six additional minor QTL were identified. Our results revealed the feasibility of selecting for enhanced vitamin E content in sunflower seeds. Increased vitamin E levels are under oligogenic control and show moderate to high heritabilities, which anticipates good prospects for introgressing the trait into sunflower elite lines. The identification of a major QTL is a promising starting point for identifying the main gene underlying increased vitamin E content and for developing diagnostic markers to assist in backcrossing programmes. The role and consistency of minor QTL should be further investigated. Sunflower oils with naturally high levels of vitamin E possess potential market niches. This research led to the isolation of a line with increased seed vitamin E content and contributed to the identification of the genetic basis underlying the trait, which is a good starting point for future breeding advances in this field.

Peer Reviewed