Two new inbred lines, T589 (medium β-tocopherol content) and T2100 (high γ-tocopherol content), recently developed in CSIC, Cordoba, Spain, have been crossed to known tph1 and tph2 mutations which possessed the same phenotypes and which were obtained at VNIIMK, Krasnodar, Russia. Genetic identification of these recessive mutations with TLC profiles showed the new medium β-tocopherol mutation to be allelic to tph1 and the new high γ-tocopherol mutation to be allelic to tph2.

Tocopherols are antioxidants that preserve oil lipids against oxidation and serve as a natural source of vitamin E in the human diet. Compared with other major oilseeds like rapeseed and soybean, sunflower (Helianthus annuus L.) exhibits low phenotypic diversity of tocopherol composition, both in wild and cultivated accessions from germplasm collections. Two major mutations that alter tocopherol composition were identified in genetic collections, and several studies suggested additional loci controlling tocopherol composition, with their expression possibly depending on the genetic background. In the present study, we performed QTL mapping of tocopherol composition in two independent F2 crosses between lines with contrasting tocopherol composition from the Pustovoit All-Russia Research Institute of Oil Crops (VNIIMK) collection. We used genotyping-by-sequencing (GBS) to construct single nucleotide polymorphism (SNP) based genetic maps, and performed QTL mapping using quantitative and qualitative encoding for phenotypic traits. Our results support the notion that the tocopherol composition in the assessed crosses is controlled by two loci. We additionally selected and validated two SNP markers for each cross which could be used for marker assisted selection.

Influences of genetic background, ontogenesis and environment on tocopherol mutations in sunflower were estimated in this study. The content of α/β-tocopherols varied from 40/60 to 60/40% in seeds of different inbred lines containing the tph1 gene. The lines containing the tph2 gene ranged widely in α/γ-tocopherols, from 0/100 to 80/20%. A double mutation showed variability in different inbred lines in α/β/γ/δ-tocopherol contents from maximum expressivity of 0/0/60/40 to minimum 40/25/25/10%, due to incomplete expressivity of tph2. Seed maturation from 10 to 38 DAF influenced tocopherol composition in both normal and mutant genotypes by increasing the α-tocopherol content. The content varied from 81 to 97% in a normal genotype, from 33 to 50% in tph1 mutation and from 0 to 6% in tph2 mutation. Tocopherol mutations were shown to express their phenotype in different parts of a plant. All roots, hypocotyls, leaves, pollen and callus from the seeds, hypocotyls and leaves had normal, tph1, tph2 and double mutation tocopherol profiles depending on the genotype. The only exception was the absence of tph1 expressivity in the green tissue of the leaves. The experiment with day/night temperatures varying during seed development from 20/18 to 30/26°C showed an increased α-tocopherol content from 39 to 48% in tph1 mutation. Both a normal genotype (about 97% of α-tocopherol) and tph2 mutation (about 98% of γ-tocopherol) were constant in these two temperature regimes. Genetic background was the main factor that influenced the expressivity of tph2 in sunflower.

МАСЛИЧНЫЕ КУЛЬТУРЫ. Научно-технический бюллетень Всероссийского научно-исследовательского института масличных культур. Вып. 1 (173), 2018

The objective of this research was to check possibilities of combining imidazolinone resistance with mutations for seed oil quality characters in sunflower. An imidazolinone resistant line HA425 (ImrImr) with normal fatty acid and tocopherol compositions was used as female after hand emasculation. An imidazolinone susceptible inbred line VK876 with high oleic content and changed tocopherol composition (OlOl tph1tph1 tph2tph2) served as male. Linkage test in the F 2 and F 3 generations has shown the Imr gene for imidazolinone resistance to be independently inherited from the high oleic mutation Ol, high β-tocopherol mutation tph1 and high γ-tocopherol mutation tph2. Recombinant genotypes have been selected for development of inbred lines.