Tocopherols are the most important compounds having antioxidant activity in sunflower seeds. The objective of the present research was to study the genetic and environmental variation for tocopherol content and composition in sunflower. Thirty-six sunflower hybrids were grown at 13 locations across all major areas of sunflower cultivation in southern Spain. Seed yield, 100 seed weight, oil content and tocopherol content and composition were determined. Tocopherol content ranged from 314·5 to 1024·5 mg/kg seed and from 562·8 to 1872·8 mg/kg oil. The tocopherol fraction was largely composed of alpha-tocopherol, which accounted for 88·4% to 96·3% of the total tocopherols. Both genotypic and environmental effects were significant for tocopherol content and composition. For alpha-, beta- and total tocopherol content, the effect of the genotype was larger than that of the environment, whereas the latter had a greater effect on gamma-tocopherol content. Genotype×location interaction was significant for alpha-, gamma- and total tocopherol content. Tocopherol content was not correlated with seed oil or seed yield, indicating the possibility of selecting for this trait without affecting the performance of the genotypes.

Different races of the parasitic Orobanche cumana (sunflower broomrape) have been reported in Spain, race F being the most virulent. Full resistance in sunflower to races A-E is achieved with each of the single major genes Or 1 to Or 5 respectively. However, parasitised hybrids allegedly resistant to race F were observed in early 2002. The purpose of this study was to verify broomrape incidences (BI) on resistant sunflower genotypes, to assess the mixture of races within field populations and to test for partial resistance to race F in the sunflower hybrids showing a low degree of attack (DA) by the weed. Tests were conducted under field conditions in two locations of southern Spain. While no significant differences were found for yield and BI between locations, the DA on the cultivars depended on the location. With high infection levels and significantly lower yield in susceptible controls, marked differences in BI and DA were found within resistant cultivars, but all of them showed similar crop yield. When artificially inoculated with several populations of race F, line P96 and mainly line L86, were consistently slightly infected, suggesting they were inbred lines responsible for horizontal resistance in infested fields. L86 was extremely susceptible to race E populations, which is unusual as sunflower resistance to one race provided resistance to all the previously described races of O. cumana. No different virulences were detected within two groups of subpopulations (races E and F) inoculated onto resistant sunflower genotypes. However, race F subpopulations showed significant differences in aggressiveness, which seems to be related to horizontal (multigenic) resistance of the crop to the parasitic weed.

No abstract

The production of sunflower is threatened by Orobanche cumana (broomrape) infections in many countries of southern and eastern Europe. The most virulent race of this parasitic weed, race F, is widespread in Spain. Most of the current commercial hybrids of resistant sunflower do not completely prevent broomrape emergence in the field. The performance (broomrape incidence and severity, final yields and oil contents) of four resistant and two susceptible sunflower hybrids was studied in different years in several O. cumana -infested locations. O. cumana -sunflower interactions were characterised by low severity and intermediate incidence in the resistant hybrids; both depended on the environment. An increase in sunflower yield because of the use of resistant hybrids was most noticeable under heavy field infestations and under drought. Characterisation of 20 populations of O. cumana classified as race F in terms of the standardised area under the degree of attack progress curve (SAUDC) and O. cumana incidence (BI) suggested differential intrinsic pathogenicities. These results highlight the variability within race F of O. cumana, mirroring the environmentally dependent horizontal resistance in sunflower.LSD, least significant difference.LSDs for comparing seed yield were: 184.2, 131.1 and 169.9, for environment, hybrid and environment · hybrid respectively.LSDs for comparing oil content were: 1.1, 0.7 and 1.8, for environment, hybrid and environment · hybrid respectively.LSDs for comparing oil yield were: 99.3, 63.2 and 167.0, for environment, hybrid and environment · hybrid respectively.474 M L Molinero-Ruiz et al.