Seed Tocopherol Content Research Articles

QTL Mapping for Seed Tocopherol Content in Soybean

Tocopherol plays an important role as a powerful antioxidant in human beings and in plants. This study investigated the genetic basis of tocopherol content in soybean. A RIL population of 192 lines derived from 2 cultivars, ZH13 and ZH35, was evaluated for tocopherol content across 3 environments. QTL mapping identified 38 QTL for tocopherol, with stable QTL identified on Chromosomes 5 and 12. Ninety polymorphic genes were identified from these regions. Further SNP variation of a natural population identified 47 SNPs, with missense variants in 19 genes, including the heat shock transcription factor gene (GmHSFA8) and gamma-tocopherol methyltransferase (GmVTE4), potentially related to tocopherol accumulation in soybean. Haplotype analysis revealed significant variations in these missense variants in the natural population. This study provides insights into the genetic mechanisms underlying tocopherol content in soybean, which is important for breeding high tocopherol soybean cultivars.

Identification of Genomic Loci and Candidate Genes Related to Seed Tocopherol Content in Soybean.

Soybean seeds are primary sources of natural tocopherols used by the food and pharmaceutical industries, owing to their beneficial impacts on human health. Selection for higher tocopherol contents in seeds along with other desirable traits is an important goal in soybean breeding. In order to identify the genomic loci and candidate genes controlling tocopherol content in soybean seeds, the bulked-segregant analysis technique was performed using a natural population of soybean consisting of 1525 accessions. We constructed the bulked-segregant analysis based on 98 soybean accessions that showed extreme phenotypic variation for the target trait, consisting of 49 accessions with extremely-high and 49 accessions with extremely-low tocopherol content. A total of 144 variant sites and 109 predicted genes related to tocopherol content were identified, in which a total of 83 genes were annotated by the gene ontology functions. Furthermore, 13 enriched terms (p < 0.05) were detected, with four of them found to be highly enriched: response to lipid, response to abscisic acid, transition metal ion transmembrane transporter activity, and double-stranded DNA binding. Especially, six candidate genes were detected at 41.8–41.9 Mb genomic hotspots on chromosome 5 based on ANNOtate VARiation analysis. Among the genes, only Glyma.05G243400 carried a non-synonymous mutation that encodes a “translation elongation factor EF1A or initiation factor IF2gamma family protein” was identified. The haplotype analysis confirmed that Glyma.05G243400 exhibited highly significant variations in terms of tocopherol content across multiple experimental locations, suggesting that it can be the key candidate gene regulating soybean seed tocopherols. The present findings provide novel gene resources related to seed tocopherols for further validation by genome editing, functional characterization, and genetic improvement targeting enhanced tocopherol composition in soybean molecular breeding.

QTL and Candidate Genes for Seed Tocopherol Content in 'Forrest' by 'Williams 82' Recombinant Inbred Line (RIL) Population of Soybean.

Soybean seeds are rich in secondary metabolites which are beneficial for human health, including tocopherols. Tocopherols play an important role in human and animal nutrition thanks to their antioxidant activity. In this study, the ‘Forrest’ by ‘Williams 82’ (F×W82) recombinant inbred line (RIL) population (n = 306) was used to map quantitative trait loci (QTL) for seed α-tocopherol, β-tocopherol, δ -tocopherol, γ-tocopherol, and total tocopherol contents in Carbondale, IL over two years. Also, the identification of the candidate genes involved in soybean tocopherols biosynthetic pathway was performed. A total of 32 QTL controlling various seed tocopherol contents have been identified and mapped on Chrs. 1, 2, 5, 6, 7, 8, 9, 10, 12, 13, 16, 17, and 20. One major and novel QTL was identified on Chr. 6 with an R2 of 27.8, 9.9, and 6.9 for δ-tocopherol, α-tocopherol, and total tocopherol content, respectively. Reverse BLAST analysis of the genes that were identified in Arabidopsis allowed the identification of 37 genes involved in soybean tocopherol pathway, among which 11 were located close to the identified QTLs. The tocopherol cyclase gene (TC) Glyma.06G084100 is located close to the QTLs controlling δ-tocopherol (R2 = 27.8), α-tocopherol (R2 = 9.96), and total-tocopherol (R2 = 6.95). The geranylgeranyl diphosphate reductase (GGDR) Glyma.05G026200 gene is located close to a QTL controlling total tocopherol content in soybean (R2 = 4.42). The two methylphytylbenzoquinol methyltransferase (MPBQ-MT) candidate genes Glyma.02G002000 and Glyma.02G143700 are located close to a QTL controlling δ-tocopherol content (R2 = 3.57). The two γ-tocopherol methyltransferase (γ-TMT) genes, Glyma.12G014200 and Glyma.12G014300, are located close to QTLs controlling (γ+ß) tocopherol content (R2 = 8.86) and total tocopherol (R2 = 5.94). The identified tocopherol seed QTLs and candidate genes will be beneficial in breeding programs to develop soybean cultivars with high tocopherol contents.

Quantitative trait loci underlying soybean seed tocopherol content with main additive, epistatic and QTL × environment effects

AbstractSoybean (Glycine max [L.] Merrill) seeds are a major source of tocopherols (Toc), which could significantly improve immune system health of human and prevent or treat many serious diseases. Selection for higher Toc contents of seeds could increase nutritional value of soybean‐derived food, laying on an important breeding goal for many soybean breeders. The present objectives of the work were to evaluate various genetic effects of QTL associated with individual and total Toc content based on a RIL population (“Beifeng 9” × “Freeborn”) in six environments to improve the efficiency of molecular marker‐assisted selection (MAS) for high‐Toc breeding. The results described that eighteen, thirteen, eleven and thirteen QTL were associated with α‐Toc, γ‐Toc, δ‐Toc and total Toc content, respectively, and have additive main effects (a) and/or additive × environment interaction effects (ae) in certain environments. Among them, four QTL for α‐Toc, two QTL for γ‐Toc, one QTL for δ‐Toc and four QTL for total Toc could increase α‐Toc, γ‐Toc, δ‐Toc and total Toc content via significant a effect, respectively, which have stronger stability in different years and locations. It implied a value for MAS. Additionally, twenty‐five, fifteen, eleven and twenty epistatic pairwise QTL associated with α‐Toc, γ‐Toc, δ‐Toc and total Toc contents, respectively, were detected. The genetic information of the QTL effects obtained here would be beneficial for breeding soybean variety with high‐Toc content by MAS.

Marked differences in seed dormancy in two populations of the Mediterranean shrub, Cistus albidus L.

Background: Population structure and dynamics in natural ecosystems can be affected by seed viability and dormancy. However, how the endogenous contents of phytohormones and vitamin E in seeds relative to the environment affect viability and dormancy is not yet fully understood.Aims: We studied seed viability and germination capacity in two populations of the Mediterranean shrub, Cistus albidus, exposed to contrasting environmental conditions.Methods: We measured seed viability and germination capacity and endogenous contents of abscisic acid (ABA), gibberellins and vitamin E in seeds collected from two populations, in two environmentally contrasting environments in north-eastern Spain.Results: Plants growing in the natural site produced seeds with lower germination percentage but similar viability, indicating higher seed dormancy. Enhanced seed dormancy was paralleled with higher contents of ABA and lower contents of gibberellins (GAs). Contents of tocopherols and tocotrienols were higher in seeds of the natural population. Tocopherol contents in seeds correlated positively with the ratio living:total aerial biomass.Conclusions: Two Mediterranean populations of C. albidus growing in two sites with contrasting environmental conditions showed marked differences in seed dormancy and germination, which may be explained, at least in part, by differences in seed hormonal contents.

Remobilization of Phytol from Chlorophyll Degradation Is Essential for Tocopherol Synthesis and Growth of Arabidopsis

Phytol from chlorophyll degradation can be phosphorylated to phytyl-phosphate and phytyl-diphosphate, the substrate for tocopherol (vitamin E) synthesis. A candidate for the phytyl-phosphate kinase from Arabidopsis thaliana (At1g78620) was identified via a phylogeny-based approach. This gene was designated VITAMIN E DEFICIENT6 (VTE6) because the leaves of the Arabidopsis vte6 mutants are tocopherol deficient. The vte6 mutant plants are incapable of photoautotrophic growth. Phytol and phytyl-phosphate accumulate, and the phytyl-diphosphate content is strongly decreased in vte6 leaves. Phytol feeding and enzyme assays with Arabidopsis and recombinant Escherichia coli cells demonstrated that VTE6 has phytyl-P kinase activity. Overexpression of VTE6 resulted in increased phytyl-diphosphate and tocopherol contents in seeds, indicating that VTE6 encodes phytyl-phosphate kinase. The severe growth retardation of vte6 mutants was partially rescued by introducing the phytol kinase mutation vte5. Double mutant plants (vte5 vte6) are tocopherol deficient and contain more chlorophyll, but reduced amounts of phytol and phytyl-phosphate compared with vte6 mutants, suggesting that phytol or phytyl-phosphate are detrimental to plant growth. Therefore, VTE6 represents the missing phytyl-phosphate kinase, linking phytol release from chlorophyll with tocopherol synthesis. Moreover, tocopherol synthesis in leaves depends on phytol derived from chlorophyll, not on de novo synthesis of phytyl-diphosphate from geranylgeranyl-diphosphate.

Development of Selectable Marker-Free Transgenic Rice Plants with Enhanced Seed Tocopherol Content through FLP/FRT-Mediated Spontaneous Auto-Excision.

Development of marker-free transgenic plants is a technical alternative for avoiding concerns about the safety of selectable marker genes used in genetically modified (GM) crops. Here, we describe the construction of a spontaneous self-excision binary vector using an oxidative stress-inducible modified FLP/FRT system and its successful application to produce marker-free transgenic rice plants with enhanced seed tocopherol content. To generate selectable marker-free transgenic rice plants, we constructed a binary vector using the hpt selectable marker gene and the rice codon-optimized FLP (mFLP) gene under the control of an oxidative stress-inducible promoter between two FRT sites, along with multiple cloning sites for convenient cloning of genes of interest. Using this pCMF binary vector with the NtTC gene, marker-free T1 transgenic rice plants expressing NtTC were produced by Agrobacterium-mediated stable transformation using hygromycin as a selective agent, followed by segregation of selectable marker genes. Furthermore, α-, γ-, and total tocopherol levels were significantly increased in seeds of the marker-free transgenic TC line compared with those of wild-type plants. Thus, this spontaneous auto-excision system, incorporating an oxidative stress-inducible mFLP/FRT system to eliminate the selectable marker gene, can be easily adopted and used to efficiently generate marker-free transgenic rice plants. Moreover, nutritional enhancement of rice seeds through elevation of tocopherol content coupled with this marker-free strategy may improve human health and public acceptance of GM rice.

Unraveling the Genetic Basis of Seed Tocopherol Content and Composition in Rapeseed (Brassica napus L.)

BackgroundTocopherols are important antioxidants in vegetable oils; when present as vitamin E, tocopherols are an essential nutrient for humans and livestock. Rapeseed (Brassica napus L, AACC, 2 n = 38) is one of the most important oil crops and a major source of tocopherols. Although the tocopherol biosynthetic pathway has been well elucidated in the model photosynthetic organisms Arabidopsis thaliana and Synechocystis sp. PCC6803, knowledge about the genetic basis of tocopherol biosynthesis in seeds of rapeseed is scant. This project was carried out to dissect the genetic basis of seed tocopherol content and composition in rapeseed through quantitative trait loci (QTL) detection, genome-wide association analysis, and homologous gene mapping.Methodology/Principal FindingsWe used a segregating Tapidor × Ningyou7 doubled haploid (TNDH) population, its reconstructed F2 (RC-F2) population, and a panel of 142 rapeseed accessions (association panel). Genetic effects mainly contributed to phenotypic variations in tocopherol content and composition; environmental effects were also identified. Thirty-three unique QTL were detected for tocopherol content and composition in TNDH and RC-F2 populations. Of these, seven QTL co-localized with candidate sequences associated with tocopherol biosynthesis through in silico and linkage mapping. Several near-isogenic lines carrying introgressions from the parent with higher tocopherol content showed highly increased tocopherol content compared with the recurrent parent. Genome-wide association analysis was performed with 142 B. napus accessions. Sixty-one loci were significantly associated with tocopherol content and composition, 11 of which were localized within the confidence intervals of tocopherol QTL.Conclusions/SignificanceThis joint QTL, candidate gene, and association mapping study sheds light on the genetic basis of seed tocopherol biosynthesis in rapeseed. The sequences presented here may be used for marker-assisted selection of oilseed rape lines with superior tocopherol content and composition.

Quantitative Trait Loci for Seed Tocopherol Content in Sunflower

ABSTRACTTocopherols are natural antioxidants with vitamin E activity. Sunflower seeds contain predominantly α‐tocopherol (&gt;950 g kg−1 tocopherols), which is the tocopherol form exhibiting the highest vitamin E activity. The objective of this research was to study the genetic basis of total seed tocopherol content in sunflower (Helianthus annuus L.). Quantitative trait loci (QTL) analysis was conducted in two mapping populations derived from crosses between lines with increased (IAST‐413) and reduced (IAST‐522) tocopherol content and the conventional sunflower line HA‐89. Tocopherol content was measured in the F2 and the F3 generations. Linkage maps were constructed using simple sequence repeat and insertion‐deletion polymorphism markers. Seven and six QTL determining increased and reduced seed tocopherol content, respectively, were identified. Of these, a major QTL on linkage group (LG) 10 was responsible for more than half the explained phenotypic variation for increased tocopherol content in the IAST‐413 × HA‐89 population, whereas a major QTL on LG 11 was responsible for more than half the explained phenotypic variation for reduced seed tocopherol content in the IAST‐522 × HA‐89 population. Three QTLs on LG 2, 4, and 17 were found in both mapping populations at overlapping support intervals. A 2‐methyl‐6‐phytyl‐1,4‐benzoquinone/2‐methyl‐6‐solanyl‐1,4‐benzoquinonone methyltransferase (MT‐2) locus was found co‐locating with the QTL on LG 4. Quantitative trait loci information from this research will contribute to the development of marker‐assisted selection tools for total tocopherol content in sunflower seeds.

A candidate gene-based association study of tocopherol content and composition in rapeseed (Brassica napus)

Rapeseed (Brassica napus L.) is the most important oil crop of temperate climates. Rapeseed oil contains tocopherols, also known as vitamin E, which is an indispensable nutrient for humans and animals due to its antioxidant and radical scavenging abilities. Moreover, tocopherols are also important for the oxidative stability of vegetable oils. Therefore, seed oil with increased tocopherol content or altered tocopherol composition is a target for breeding. We investigated the role of nucleotide variations within candidate genes from the tocopherol biosynthesis pathway. Field trials were carried out with 229 accessions from a worldwide B. napus collection which was divided into two panels of 96 and 133 accessions. Seed tocopherol content and composition were measured by HPLC. High heritabilities were found for both traits, ranging from 0.62 to 0.94. We identified polymorphisms by sequencing selected regions of the tocopherol genes from the 96 accession panel. Subsequently, we determined the population structure (Q) and relative kinship (K) as detected by genotyping with genome-wide distributed SSR markers. Association studies were performed using two models, the structure-based GLM + Q and the PK-mixed model. Between 26 and 12 polymorphisms within two genes (BnaX.VTE3.a, BnaA.PDS1.c) were significantly associated with tocopherol traits. The SNPs explained up to 16.93% of the genetic variance for tocopherol composition and up to 10.48% for total tocopherol content. Based on the sequence information we designed CAPS markers for genotyping the 133 accessions from the second panel. Significant associations with various tocopherol traits confirmed the results from the first experiment. We demonstrate that the polymorphisms within the tocopherol genes clearly impact tocopherol content and composition in B. napus seeds. We suggest that these nucleotide variations may be used as selectable markers for breeding rapeseed with enhanced tocopherol quality.

Expression of modified tocopherol content and profile in sunflower tissues

Alpha-tocopherol is the predominant tocopherol form in sunflower seeds. Sunflower lines that accumulate increased levels of beta-, gamma- and delta-tocopherol in seeds as well as lines with reduced and increased total seed tocopherol content have been developed. The objective of this research was to evaluate whether the modified tocopherol levels are expressed in plant tissues other than seeds. Lines with increased levels of beta-, gamma- and delta-tocopherol in seeds also possessed increased levels of these tocopherols in leaves, roots and pollen. Correlation coefficients for the proportion of individual tocopherols in different plant tissues were significantly positive in all cases, ranging from 0.68 to 0.97. A line with reduced tocopherol content in seeds also showed reduced content in roots and pollen. Genetic modifications producing altered seed tocopherol profiles in sunflower are also expressed in leaves, roots and pollen. Reduced total seed tocopherol content is mainly expressed at the root and pollen level. The expression of tocopherol mutations in other plant tissues will enable further studies on the physiological role of tocopherols and could be of interest for early selection for these traits in breeding programmes.

Inheritance of increased seed tocopherol content in sunflower line IAST‐413

With 1 figure and 1 tableAbstractSunflower seeds and oil are one of the richest natural food sources of alpha‐tocopherol (vitamin E). The sunflower line IAST‐413, with enhanced alpha‐tocopherol content, was developed by pedigree selection. The objective of this research was to study the inheritance of increased tocopherol content in seeds of IAST‐413. Plants of this line were reciprocally crossed with plants of line HA89 with wild‐type tocopherol content, and their F1, F1r, F2, F2r, BCP1 and BCP2 generations were evaluated in the field in 2006 and 2007. The F3 generation was evaluated in the field in 2007. Estimated broad‐sense heritability () was 0.78 in 2006 and 0.67 in 2007, whereas narrow‐sense heritability () was 0.70 in 2006 and 0.60 in 2007. Estimate of heritability through parent–offspring correlation was 0.67 and realized heritability was 0.64. The estimated minimum number of genes conditioning increased levels of tocopherol was 1.04 in 2006 and 1.95 in 2007. This mode of inheritance and response to selection should facilitate the introgression of the trait into elite germplasm to develop sunflower oil naturally rich in vitamin E.

Fatty acids, tocopherol, and sterol contents of some Nigella species seed oil

The lipid compositions of the seed oils of some Nigella species were investigated. The total oil content of the seeds ranged from 28.0 to 36.4%. GC-MS fatty acid compositional analysis of the Nigella seed oils revealed the content of linoleic acid to be the highest (40.3&amp;ndash;58.9%). Other prominent fatty acids were as follows: oleic (18.7&amp;ndash;28.1%), palmitic (10.1&amp;ndash;12.5%), 22:1 D11 (3.2&amp;ndash;3.8%) and stearic (2.6&amp;ndash;3.1%) acids. All the Nigella seed oils analysed exhibited differences in their tocopherol contents and the differences were estimated. The oils extracted from the seeds contained between 1.70&amp;ndash;4.12 mg/100 g &amp;alpha;-T, 0.97&amp;ndash;4.51 mg/100 g &amp;gamma;-T, and 4.90&amp;ndash;17.91 mg/100 g &amp;beta;-T3. The total tocopherol content in seeds varied between 9.15 mg/100 g to 24.65 mg/100 g. The compositions of the sterol fractions were determined by gas liquid chromatography. The total amounts of sterols ranged between 1993.07 mg/kg to 2182.17 mg/kg. The main component was &amp;beta;-sitosterol (48.35&amp;ndash;51.92%), followed by 5-avenasterol, campesterol, and stigmasterol.

Selection for contrasting seed tocopherol content in sunflower seeds

SUMMARYSunflower oil, with more than 0·9 of tocopherols in the alpha-tocopherol form, supplies more vitamin E than any other vegetable oil. Thus far, no breeding to increase vitamin E levels in sunflower seeds has been conducted. The objective of the present research was to develop sunflower lines with high and low total seed tocopherol content through evaluation and subsequent selection of a large germplasm collection (952 sunflower entries). A range of variation from 119 to 491 mg/kg was found. Selection conducted from S1 to S4 plant generations allowed the isolation of line IAST-413, with an increased tocopherol content of 467 mg/kg compared to 251 mg/kg in the control line HA89, and line IAST-522, with a reduced tocopherol content of 73 mg/kg. Another accession with potentially high tocopherol content, but completely self-incompatible, was crossed to the line HA89 followed by plant-to-row selection up to the F5 plant generation; it averaged 463 mg/kg compared to 240 mg/kg in HA89. Two field experiments carried out at Córdoba in southern Spain in 2006 and 2007 with different sowing dates confirmed that the increased tocopherol content in the selected lines was consistently expressed across environments.

The effect of nitrogen fertilization on tocopherols in rapeseed genotypes

Tocopherols (α-, β-, γ- and δ-tocopherol) are naturally occuring antioxidants in vegetable oils. In rapeseed oil, α- and γ-tocopherols are the predominant isomers, while δ-tocopherol contributes much lower amounts to the total tocopherol content. Enhanced tocopherol content in seeds appears favourable, and breeding for tocopherol content has become an increasingly important objective in winter oilseed rape. The main objectives of this research were to quantify the amount of tocopherols in a number of rapeseed varieties and to investigate the effect of nitrogen fertilization on tocopherol concentration in the seed. The field trials were carried out in 2004–2005 and 2005–2006 at Dardanos, Canakkale on the Turkish West Coast (10 km south of the city centre) with 13 varieties, three replications and three nitrogen levels (N0: 0 kg/ha, N1: 130 kg/ha and N2: 260 kg/ha). The trial used a randomized complete block design with 6 m2 plots. Tocopherol analysis was done using an HPLC system. Significant differences were found among the varieties and between the nitrogen levels. The average total tocopherol concentration was 118.7 mg kg−1 for N1, 134.1 mg kg−1 for N2 and 133.6 mg kg−1 for N3 fertilization level. MDS analysis indicated a rough grouping of line versus hybrid varieties and suggested that hybrids require more breeding effort to reach the level of tocopherols existed in line varieties.

Genetic basis for natural variation in seed vitamin E levels in Arabidopsis thaliana

Vitamin E is an essential nutrient for humans and is obtained primarily from food, especially oil, derived from the seed of plants. Genes encoding the committed steps in vitamin E synthesis in plants (VTE, loci 1-5) have been isolated and used for tocopherol pathway engineering with various degrees of success. As a complement to such approaches we have used quantitative trait loci analysis with two sets of Arabidopsis thaliana recombinant inbred lines and have identified 14 QVE (quantitative vitamin E) loci affecting tocopherol content and composition in seeds. Five QVE intervals contain VTE loci that are likely QVE gene candidates. Nine QVE intervals do not contain VTE loci and therefore identify novel loci affecting seed tocopherol content and composition. Several near-isogenic lines containing introgressions of the accession with increased vitamin E levels were shown to confer significantly elevated tocopherol levels compared with the recurrent parent. Fine-mapping has narrowed QVE7 (a gamma-tocopherol quantitative trait loci) to an 8.5-kb interval encompassing two genes. Understanding the basis of the QVE loci in Arabidopsis promises to provide insight into the regulation and/or metabolism of vitamin E in plants and has clear ramifications for improving the nutritional content of crops through marker-assisted selection and metabolic engineering.

Tocopherol contents of some Turkish wine by-products

The aim of this study was to determine the tocopherol contents of wine by-products including grape seed, pomace (seed, skin and stem) and bagasse (skin and stem) by using two different extraction methods in order to evaluate the possibilities of them as natural non-polar antioxidants. Cold extraction appeared to give more tocopherol contents in seeds than hot extraction. But hot extraction was found more suitable for pomace and bagasse. α-Tocopherol was the most abundant tocopherol in the grape seed, pomace and bagasse. Although γ- and δ-tocopherols were found in the samples with low concentrations, β-tocopherol was not detected in the samples. Kalecik karasi had the highest α and total tocopherol compared to the other cultivars. On the other hand, hot extracted bagasse in all cultivars gave the highest tocopherol contents. As a conclusion, wine by-products, a large scale wastes, can be evaluated both to get natural tocopherol source and to obtain economical gain.

Diallel Analysis for Tocopherol Contents in Seeds of Rapeseed

Because of their nutritional and antioxidative properties, tocopherol production is an interesting trait for the lipid quality of oil crops. Total tocopherol content in rapeseed (Brassica napus L.) is medium to low, and therefore, higher levels of tocopherol are desirable in this species. The objective of the present study was to determine the inheritance of α‐, γ‐, and total tocopherol content and the α‐/γ‐tocopherol ratio in seed of rapeseed. Two diallel mating designs with six parents each were used. In Diallel I, the parents selected were high or low for total tocopherol content and in Diallel II, the parents were high or low for the α‐/γ‐tocopherol ratio. Parents and F1 hybrids were tested in a screenhouse in 1998 and under field conditions in 1999 by means of a completely randomized design with two replications. In addition, 10 selected F2 populations were grown along with their respective parents. Compared with the parents, the F1 hybrids showed a significantly higher γ‐tocopherol content of about 6 mg kg−1 seed for Diallel I and 24 mg kg−1 seed for Diallel II. General combining ability effects in both diallels were highly significant (P &lt; 0.01) and much larger than specific combining ability effects for all traits studied. Reciprocal effects were not statistically significant. γ‐Tocopherol was not correlated with α‐tocopherol. The results indicate that tocopherol content and composition inheritances are strongly associated with additive gene action in rapeseed.

Genetic variability of tocopherol composition in sunflower seeds as a basis of breeding for improved oil quality

AbstractThe variability of seed tocopherol content in wild sunflower species, the expressivity of tph1 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. Tph1, Tph2, and Ol, 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 of the α‐homologue (90‐99%). The genetic background of different near‐isogenic lines was found to influence expressivity of mutations for tocopherol composition. High content of strong antioxidants, such as β‐, γ‐, and δ‐tocopherols increased oil oxidative stability 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.