Genetic Control of Water-Soluble Carbohydrate Reserves in Bread Wheat

Abstract

The combination of high temperatures and lack of water decrease leaf area and reduce carbon assimilation in a terminal drought. It has been suggested that selection for greater stem storage of water soluble carbohydrate (WSC) would result in improved grain-filling and increased yields in drought-prone environments. No study has reported the extent or nature of genotypic variation for WSC in wheat. Progeny from three populations were genotyped with between 450 and 950 polymorphic molecular markers and pheno-typed for stem WSC in well-watered environments. The range of WSC among progeny was large contributing to moderate to high narrow-sense heritabilities within environments (h(2) = 0.58 to 0.77); while relatively small genotype x environment interactions increased heritability on a genotype-mean basis (0.67 to 0.83). Large transgressive segregation suggested that stem WSC is controlled by multiple loci. Genetic control was complex with between 7 and 10 significant QTL (e.g. chromosomes 1A, 113, 2B, 21), 413, 7A and 7B) identified for WSC across populations and environments. QTL were generally of small effect, each accounting for between 3 and 28% of the genotypic variance. Progeny with high WSC produced higher grain weight and larger diameter, significantly reducing grain shrivelling. High heritability indicates potential for pheno-typic selection of WSC among families in breeding programs that target adaptation to terminal droughts