The variabihty of seed tocopherol content in wild sunflower species, the expressivity of tph\ and tph2 mutations in different lines and the oxidative stability of sunflower oil with altered tocopherol and fatty acid composition were objectives of this research.Near-isogenic lines for three genes, i.e. Tphl, Tphl, and 01, were developed and investigated. Tocopherol content was determined with TLC and HPLC, as well as fatty acid composition with GC of methyl esters. Rancimat tests were used to estimate the oxidative stability of the oil.The seed tocopherol composition of wild sunflower species was shown to be uniform with a prevailing content ofthe a-homologue (90-99%). The genetic background of different near-isogenic hnes was found to influence expressivity of mutations for tocopherol composition. High content of strong antioxidants, such as ^-, y-, and (5-tocopherols increased oil oxidative stabihty of linoleic and oleic types of oil by 1.2-3.0 times.The breeding model of sunflower hybrids should include antioxidant and vitamin parameters balanced for oils of different applications.
In this study, mid-oleic and high-oleic sunflower seeds were developed with high levels of c-and d-tocopherols by traditional breeding techniques. Sunflower seeds containing various profiles of tocopherols, ranging from traditional high a, low c, low d relative to those with high c, high d, and low a, were extracted, and the crude oil evaluated for oxidative stability. After aging at 60°C, oils were measured for peroxide value and hexanal as indicators of oxidation levels. We found that when the c-tocopherol content of mid-oleic sunflower oil (MOSFO) (NuSun) was increased from its regular level of 20 to 300-700 ppm, the oxidation of the oil was decreased significantly compared to MOSFO with its regular low c-tocopherol level. The modified oils had a-tocopherol contents of up to 300 ppm without negatively affecting the stability of the oil. An oil with one of the best oxidative stabilities had a tocopherol profile of 470 ppm c, 100 ppm d, and 300 ppm a, indicating that MOSFO could be more oxidatively stable and still be a good source of Vitamin E from a-tocopherol.
The phenomenon of cytoplasmic male sterility (CMS), consisting in the inability to produce functional pollen due to mutations in mitochondrial genome, has been described in more than 150 plant species. With the discovery of nuclear fertility restorer (Rf) genes capable of suppressing the CMS phenotype, it became possible to use the CMS-Rf genetic systems as the basis for practical utilization of heterosis effect in various crops. Seed production of sunflower hybrids all over the world is based on the extensive use of the PET1 CMS combined with the Rf1 gene. At the same time, data on Rf1 localization, sequence, and molecular basis for the CMS PET1 type restoration of fertility remain unknown. Searching for candidate genes of the Rf1 gene has great fundamental and practical value. Therefore, in this study, association mapping of fertility restorer gene for CMS PET1 in sunflower was performed. The genome-wide association study (GWAS) results made it possible to isolate a segment 7.72 Mb in length on chromosome 13, in which 21 candidates for Rf1 fertility restorer gene were identified, including 20 pentatricopeptide repeat (PPR)family genes and one Probable aldehyde dehydrogenase gene. The results will serve as a basis for further study of the genetic nature and molecular mechanisms of pollen fertility restoration in sunflower, as well as for further intensification of sunflower breeding.
Development of genetic collection is considered to be an essential part of genetic resources of cultivated sunflower. The VNIIMK genetic collection of identified alleles determining oleic acid content in the seed oil consists of about 50 constant inbred lines. Fourteen of them are in a core collection. The general range of this trait varies from 20 to 92%. These inbred lines correspond to four main phenotypic classes: low, conventional, mid and high oleic. The normal line RIL100 was shown to contain a high oleic mutation Ol in hypostatic condition. The mid oleic LG27 averagely 67% does not contain the high oleic mutation in genetic background. The high oleic LG 26 with relatively low content of oleic acid, about 86%, possesses resistance to suppressor's actions.
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.
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