QTL mapping of protein content and seed characteristics under water-stress conditions in sunflower.

The purpose of this study was to identify genomic regions controlling seed protein content, kernel and hull weights, and seed density in water-stress conditions in sunflower (Helianthus annuus L.). The experiments consisted of a split-plot design (water treatment and recombinant inbred lines) with three blocks in two environments (greenhouse and field). High significant variation was observed between genotypes for all traits as well as for water treatment x genotype interaction. Several specific and nonspecific QTLs were detected for all traits under well-watered and water-stress conditions. Two SSR markers, ORS671_2 and HA2714, linked to protein content were identified that have no interaction with water treatments in greenhouse conditions. We also detected the E35M60_4 marker associated with kernel weight that had no interaction with water treatments. A specific QTL for protein content was detected with important phenotypic variance (17%) under water-stress conditions. Overlapping QTLs for protein content and seed density were identified in linkage group 15. This region probably has a peliotropic effect on protein content and seed density. QTLs for protein content colocated with grain weight traits were also identified.

QTL mapping of seed-quality traits in sunflower recombinant inbred lines under different water regimes.

The objectives of the present research were to determine the effects of water stress on seed-quality traits and to map QTLs controlling the studied traits under two different water treatments in a population of sunflower recombinant inbred lines (RILs). Two experiments were conducted in greenhouse and field conditions, each with well-watered and water-stressed treatments. The experiments consisted of a split-plot design (water treatment and RIL) with three blocks. Analyses of variance showed significant variation among genotypes, and a water treatment x genotype interaction was also observed for most of the traits. Two to 15 QTLs were found, depending on trait and growth conditions, and the percentage of phenotypic variance explained by the QTLs ranged from 5% to 31%. Several QTLs for oil content overlapped with QTLs for palmitic and stearic acid contents in all four conditions. An overlapping region on linkage group 3 (QTLs 2.OC.3.1 and 4.SA.3.1) was linked to an SSR marker (ORS657). A principal component analysis was performed on four fatty acid traits. Two principal components, P1 and P2, were used for QTL analysis. This method improved the ability to identify chromosomal regions affecting the fatty acids. We also detected the principal-component QTLs that did not overlap with the fatty acid QTLs. The results highlight genomic regions of interest in marker-based breeding programmes for increasing oil content in sunflower.

Genetic variability for physiological traits under drought conditions and differential expression of water stress-associated genes in sunflower (Helianthus annuus L.).

Genotypic variation for water status and gas exchange parameters under different water treatments (well-watered and water-stressed plants before and after rehydration) were investigated in a population of recombinant inbred lines (RILs) of sunflower (Helianthus annuus L.). Afterwards, four RILs and parental lines presenting contrasting responses to dehydration and rehydration were selected to determine the differential expression of four water-stress associated genes: aquaporin, dehydrin, leafy cotyledon1-like protein and fructose-1,6 bisphosphatase. Water stress revealed a high genetic variability for water status and gas exchange parameters when compared with well-watered genotypes. Genetic gain when selected RILs were compared with the best parent was significant for most traits due to transgressive segregation. QTL mapping and graphical genotyping showed that RILs carrying different genomic regions for some QTLs presented also physiological different characteristics as well as gene expression patterns. The expression level of aquaporin genes in leaves of four RILs and their parents was down regulated by water stress and was associated with relative water content (RWC). Down-regulation was also associated with genomic regions having alleles with negative effects on plant water status. The level of dehydrin transcripts increased in leaves of all studied RILs in response to water stress. Transcript accumulations of dehydrin and leafy cotyledon1-like genes, likely involved in protective tolerance processes, were not correlated directly with plant water status or QTL effects. Down-regulation of fructose-1,6 bisphosphatase was observed under water stress. Net photosynthesis rate (P(n)) and the fructose-1,6 bisphosphatase gene expression levels were associated mainly after rehydration. This phenomenon indicates an association between physiological response to water stress and differential expression of water-stress related genes.

[Comparison of the efficacy of verapamil and diltiazem in stable exercise angina. A double-blind and crossover study]. / Comparaison de l'efficacité du vérapamil et du diltiazem dans l'angor d'effort stable. Etude en double aveugle et en crossover.

Calcium channel blockers are now recommended for the treatment of stable angina but few studies have been carried out comparing the efficacy of verapamil and diltiazem in this indication. The short-term efficacy of these two drugs was compared in a double-blind crossover trial in 12 patients. The following protocol was used, 24 hour selection period followed by two crossover treatment periods versus double placebo. Exercise stress tests were performed 2 hours after the last dose at the end of each treatment period. Each patient underwent 3 stress tests: the first during the selection period whilst taking verapamil and diltiazem placebo (ET0), the second after the first treatment period at day 7 (ET1) and the third after the second treatment period at day 14 (ET2). A comparison of exercise capacity (ET0 to ET1 and ET2) showed improved effort tolerance and an increase in the ischaemic threshold with calcium blocker therapy. The duration of effort, the maximum sustained load, the rate-pressure product and the time to ST depression were all significantly increased. On the other hand, there were no significant changes in the percentage theoretical maximum heart rate attained, the heart rate at which ST depression occurred, the maximum ST depression and the incidence of angina. A comparison between ET1 and ET2 did not show any difference in the parameters of maximum effort or of the appearance of myocardial ischaemia. The comparison of exercise stress tests performed after treatment with verapamil and after diltiazem showed that the total duration of exercise, the maximum sustained load (in watts) and the rate-pressure product were identical.(ABSTRACT TRUNCATED AT 250 WORDS)