SU MMARYSunflower 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 S 1 to S 4 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 F 5 plant generation; it averaged 463 mg/kg compared to 240 mg/kg in HA89. Two field experiments carried out at Co´rdoba 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. INTRODUCTIONVitamin E is a family of fat-soluble antioxidants that protect cellular membrane lipids against oxidative damage, which has been associated with a decreased risk of developing some forms of cancer, cardiovascular diseases and degenerative processes linked to disease (Packer & Obermu¨ller-Jevic 2002). The main naturally occurring compounds with vitamin E activity are tocopherols and tocotrienols. Tocopherols occur ubiquitously in plant tissues, with the highest concentrations being found in seeds. There are four tocopherols, alpha-, beta-, gamma-and delta-tocopherol, which differ in their vitamin E activities. Alpha-tocopherol exerts the highest vitamin E activity in animals (Pongracz et al. 1995). There is a large body of medical evidence pointing to the benefits for human health associated with daily, moderate, vitamin E supplementation (Bramley et al. 2000).Gamma-tocopherol, with only one-tenth the vitamin-E activity of alpha-tocopherol (Pongracz et al. 1995), is the predominant tocopherol derivative in most oilseeds (Padley et al. 1994). Sunflower, with more than 0 . 9 of tocopherols in the alpha-tocopherol form, represents a remarkable exception. The high vitamin E content of sunflower oil is being used by some manufacturers as a claim to attract consumers, even through fortification of the oil with either natural or synthetic alpha-tocopherol. Several brands of sunflower oil fortified with alpha-tocopherol are currently being marketed in Spain. Sunflower cultivars with increased concentrations of alpha-tocopherol in the seeds would produce oils with naturally enhanced vitamin E value.The tocopherol content in the extracted seed oil is the result of several factors, the most important being the tocopherol content in the seeds, the oil content in the seeds, the oil extraction system and t...
Key message OrDeb2 confers post-attachment resistance to Orobanche cumana and is located in a 1.38 Mbp genomic interval containing a cluster of receptor-like kinase and receptor-like protein genes with nine high-confidence candidates. Abstract Sunflower broomrape is a holoparasitic angiosperm that parasitizes on sunflower roots, severely constraining crop yield. Breeding for resistance is the most effective method of control. OrDeb2 is a dominant resistance gene introgressed into cultivated sunflower from a wild-related species that confers resistance to highly virulent broomrape races. The objectives of this study were as follows: (i) locate OrDeb2 into the sunflower genome and determine putative candidate genes and (ii) characterize its underlying resistance mechanism. A segregating population from a cross between the sunflower resistant line DEB2, carrying OrDeb2, and a susceptible line was phenotyped for broomrape resistance in four experiments, including different environments and two broomrape races (FGV and GTK). This population was also densely genotyped with microsatellite and SNP markers, which allowed locating OrDeb2 within a 0.9 cM interval in the upper half of Chromosome 4. This interval corresponded to a 1.38 Mbp genomic region of the sunflower reference genome that contained a cluster of genes encoding LRR (leucine-rich repeat) receptor-like proteins lacking a cytoplasmic kinase domain and receptor-like kinases with one or two kinase domains and lacking an extracellular LRR region, which were valuable candidates for OrDeb2. Rhizotron and histological studies showed that OrDeb2 determines a post-attachment resistance response that blocks O. cumana development mainly at the cortex before the establishment of host-parasite vascular connections. This study will contribute to understand the interaction between crops and parasitic weeds, to establish durable breeding strategies based on genetic resistance and provide useful tools for marker-assisted selection and OrDeb2 map-based cloning.
With 1 figure and 1 table Abstract Sunflower 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.
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