Sterol content in sunflower seeds (Helianthus annuus L.) as affected by genotypes and environmental conditions

Phytosterols play essential roles in many plant cell mechanisms. They are of industrial interest since, as part of the diet, they can reduce Low Density Lipoprotein cholesterol. An increase in plant sterol contents by improved crop varieties or crop management could help to answer industrial demands and also to develop environmentally friendly extraction methods. The aim of this study was to evaluate genotypic variability for sterol content in cultivated sunflower and effects of sowing date, in particular sowing date. Results showed large variability among a collection of sixteen sunflower inbred lines and hybrids. Total sterols varied almost twofold between extreme genotypes. A delay of sowing, giving higher temperatures during seed formation, induced a general increase in total sterol concentration by up to 35 per cent, as well as sterol composition but this varied according to genotype. These results are discussed with the aim of improving sterol content by sunflower breeding programmes

Positional cloning of a candidate gene for resistance to the sunflower downy mildew, Plasmopara halstedii race 300.

International audienceThe resistance of sunflower to Plasmopara halstedii is conferred by major resistance genes denoted Pl. Previous genetic studies indicated that the majority of these genes are clustered on linkage groups 8 and 13. The Pl6 locus is one of the main clusters to have been identified, and confers resistance to several P. halstedii races. In this study, a map-based cloning strategy was implemented using a large segregating F2 population to establish a fine physical map of this cluster. A marker derived from a bacterial artificial chromosome (BAC) clone was found to be very tightly linked to the gene conferring resistance to race 300, and the corresponding BAC clone was sequenced and annotated. It contains several putative genes including three toll-interleukin receptor-nucleotide binding site-leucine rich repeats (TIR-NBS-LRR) genes. However, only one TIR-NBS-LRR appeared to be expressed, and thus constitutes a candidate gene for resistance to P. halstedii race 300

Ten Broad Spectrum Resistances to Downy Mildew Physically Mapped on the Sunflower Genome

Resistance to downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus L.) is conferred by major resistance genes, denoted Pl. Twenty-two Pl genes have been identified and genetically mapped so far. However, over the past 50 years, wide-scale presence of only a few of them in sunflower crops led to the appearance of new, more virulent pathotypes (races) so it is important for sunflower varieties to carry as wide a range of resistance genes as possible. We analyzed phenotypically 12 novel resistant sources discovered in breeding pools derived from two wild Helianthus species and in eight wild H. annuus ecotypes. All were effective against at least 16 downy mildew pathotypes. We mapped their resistance genes on the sunflower reference genome of 3,600 Mb, in intervals that varied from 75 Kb to 32 Mb using an AXIOM® genotyping array of 49,449 SNP. Ten probably new genes were identified according to resistance spectrum, map position, hypersensitive response to the transient expression of a P. halstedii RXLR effector, or the ecotype/species from which they originated. The resistance source HAS6 was found to carry the first downy mildew resistance gene mapped on chromosome 11, whereas the other resistances were positioned on chromosomes 1, 2, 4, and 13 carrying already published Pl genes that we also mapped physically on the same reference genome. The new genes were designated Pl23–Pl32 according to the current nomenclature. However, since sunflower downy mildew resistance genes have not yet been sequenced, rules for designation are discussed. This is the first large scale physical mapping of both 10 new and 10 already reported downy mildew resistance genes in sunflower

Comparative genetic analysis of quantitative traits in sunflower (Helianthus annuus L.)

One hundred and fifty F2–F3 families from a cross between two inbred sunflower lines FU and PAZ2 were used to map quantitative trait loci (QTL) for resistance to white rot (Sclerotinia sclerotiorum) attacks of terminal buds and capitula, and black stem (Phoma macdonaldii). A genetic linkage map of 18 linkage groups with 216 molecular markers spanning 1,937 cM was constructed. Disease resistances were measured in field experiments for S. sclerotiorum and under controlled conditions for P. macdonaldii. For resistance to S. sclerotiorum terminal bud attack, seven QTL were identified, each explaining less than 10% of phenotypic variance. For capitulum attack by this parasite, there were four QTL (each explaining up to 20% of variation) and for P. macdonaldii resistance, four QTL were identified, each having effects of up to 16%. The S. sclerotiorum capitulum resistance QTL were compared with those reported previously and it was concluded that resistance to this disease is governed by a considerable number of QTL, located on almost all the sunflower linkage groups

Gene banks for wild and cultivated sunflower genetic resources

Modern breeding of sunflower (Helianthus annuus L.), which started 100 years ago, increased the number and the diversity of cultivated forms. In addition, for more than 50 years, wild sunflower and other Helianthus species have been collected in North America where they all originated. Collections of both cultivated and wild forms are maintained in gene banks in many countries where sunflower is an important crop, with some specificity according to the availability of germplasm and to local research and breeding programmes. Cultivated material includes land races, open pollinated varieties, synthetics and inbred lines. The majority of wild accessions are ecotypes of wild Helianthus annuus, but also 52 other species of Helianthus and a few related genera. The activities of three gene banks, in USA, France and Serbia, are described in detail, supplemented by data from seven other countries. Past and future uses of the genetic resources for environmental adaptation and breeding are discussed in relation to genomic and improved phenotypic knowledge of the cultivated and wild accessions available in the gene banks.L’amélioration moderne du tournesol (Helianthus annuus L.) a débuté il y a un siècle, diversifiant et augmentant le nombre des formes cultivées du tournesol. De plus, des collectes de tournesols sauvages et d’espèces du genre Helianthus ont lieu depuis 50 ans en Amérique du Nord d’où ils sont tous originaires. Ainsi, des collections de tournesols cultivés et sauvages sont conservées par des centres de ressources génétiques dans de nombreux pays où le tournesol est une culture importante. Chacun d’eux présente des spécificités par rapport aux ressources génétiques maintenues, en fonction des programmes de recherche ou de sélection variétale locales. Le matériel génétique cultivé comprend des écotypes, des populations et des lignées tandis que les accessions sauvages correspondent eux écotypes d’Helianthus annuus sauvages et des 52 autres espèces apparentées du genre Helianthus. Les activités de trois centres de ressources génétiques des États-Unis, de la France et de la Serbie sont décrites en détail, complétées par des données provenant des centres de sept autres pays. L’historique de l’utilisation des ressources génétiques et les perspectives futures pour l’adaptation des variétés à l’environnement sont discutés ainsi que leur caractérisation au niveau génomique et phénotypique.The Supplementary Material is available at [https://www.ocljournal.org/10.1051/ocl/2020004/olm]

Classic genetics and breeding

International audienceSunflower hybrids were first developed in sunflower 60 years ago and with the discovery of cytoplasmic male sterility have become the main type of variety since 1970. Breeding programs use mostly pedigree, recurrent and backcross selection. The main characters selected for are seed yield, oil content and oil type, earliness, height, disease, insect and drought resistance. Except for a few major genes, until 1995, breeding depended only on phenotypic observations, but in the last 10 years genomics have improved knowledge of the genetics of quantitative characters and marker-assisted selection has started to become a practical tool

The effect of male sterility on oil content and seed yield in sunflowers (Helianthus annuus L.)

Measurements of oil content and seed yield of some experimental sunflower hybrids between a tester line and individuals from a population showed that the male sterile hybrids contained a mean of 2.62 % more oil than male fertile hybrids and had a higher seed yield (103.19 % of the control varieties compared with 94.97 %). Similar differences were found between inbred male sterile plants and their isogenic maintainers under self pollination (1.25 % more oil, 4.11 g/plant more seed) ans cross pollination (1.13 % more oil, 7.56 g/plant more seed). The greater oil content and seed yield of male sterile plants did not appear to be related to the cytoplasm determining male sterility nor to cross pollination it could be due to the male sterility as such

Helianthus

International audienc

The effect of male sterility on oil content and seed yield in sunflowers (Helianthus annuus L.)

Measurements of oil content and seed yield of some experimental sunflower hybrids between a tester line and individuals from a population showed that the male sterile hybrids contained a mean of 2.62 % more oil than male fertile hybrids and had a higher seed yield (103.19 % of the control varieties compared with 94.97 %). Similar differences were found between inbred male sterile plants and their isogenic maintainers under self pollination (1.25 % more oil, 4.11 g/plant more seed) ans cross pollination (1.13 % more oil, 7.56 g/plant more seed). The greater oil content and seed yield of male sterile plants did not appear to be related to the cytoplasm determining male sterility nor to cross pollination it could be due to the male sterility as such

The effect of male sterility on oil content and seed yield in sunflowers (Helianthus annuus L.)

Measurements of oil content and seed yield of some experimental sunflower hybrids between a tester line and individuals from a population showed that the male sterile hybrids contained a mean of 2.62 % more oil than male fertile hybrids and had a higher seed yield (103.19 % of the control varieties compared with 94.97 %). Similar differences were found between inbred male sterile plants and their isogenic maintainers under self pollination (1.25 % more oil, 4.11 g/plant more seed) ans cross pollination (1.13 % more oil, 7.56 g/plant more seed). The greater oil content and seed yield of male sterile plants did not appear to be related to the cytoplasm determining male sterility nor to cross pollination it could be due to the male sterility as such