Quantitative trait loci for water-soluble carbohydrates and associations with agronomic traits in wheat

Abstract

Several environmental factors including drought and disease can reduce leaf area and photosynthesis during grain-filling to decrease grain yield and kernel weight of cereal crops. Water-soluble carbohydrates (WSC) accumulated around anthesis can be mobilised to assist in filling of developing grains when post-anthesis assimilation is low. Cultivar differences support opportunities to select for high WSC but little is known of the extent or nature of genetic control for this trait in wheat. Three wheat mapping populations (Cranbrook/Halberd, Sunco/Tasman, and CD87/Katepwa) were phenotyped for WSC and other agronomic traits across multiple environments. The range for WSC concentration (WSC-C) was large among progeny contributing to moderate-to-high narrow-sense heritabilities within environments (h2 = 0.51–0.77). Modest genotype × environment interaction reduced the correlation of genotype means across environments (rp = 0.37–0.78, P < 0.01) to reduce heritability on a line-mean (h2 = 0.55–0.87) basis. Transgressive segregation was large and genetic control complex, with 7–16 QTLs being identified for WSC-C in each population. Heritability was smaller (h2 = 0.32–0.54) for WSC mass per unit area (WSC-A), reflecting large genotype × environment interaction and residual variance with estimating anthesis biomass. Fewer significant QTLs (4–8) were identified for this trait in each population, while sizes of individual genetic effects varied between populations but were repeatable across environments. Several genomic regions were common across populations including those associated with plant height (e.g. Rht-B1) and/or anthesis date (e.g. Ppd1). Genotypes with high WSC-C were commonly shorter, flowered earlier, and produced significantly (P < 0.01) fewer tillers than those of low WSC-C. This resulted in similar yields, lower final biomass, and fewer grains per m2, but greater dry weight partitioning to grain, kernel weight, and less grain screenings in high compared with low WSC-C genotypes. By contrast, lines high for WSC-A produced more fertile tillers associated with similar or greater anthesis and maturity biomass, grain number, and yield, yet similar kernel weight or size compared with genotypes with low WSC-A. The data support an important role for WSC-A in assuring stable yield and grain size. However, the small effects of many independent WSC QTLs may limit their direct use for marker-aided selection in breeding programs. We suggest using molecular markers to enrich populations for favourable height and anthesis date alleles before the more costly phenotypic selection among partially inbred families for greater WSC-A.

Preferential retention of chromosome regions in derived synthetic wheat lines: a source of novel alleles for wheat improvement

“…The 2BS region was associated with positive and negative effects on ANT, GW and GY in the present study; comparative mapping suggests that it is the same region as identified in several published studies, which contains QTLs for anthesis, height, grain weight and grain yield (Verma et al 2004;Quarrie et al 2005;Kuchel et al 2006;Rebetzke et al 2008;McIntyre et al 2010), and Ppd-B1 (Mohler et al 2004). Similarly, the 7BL region was associated with all four traits in this study.…”

More fertile florets and grains per spike can be achieved at higher temperature in wheat lines with high spike biomass and sugar content at booting

“…In wheat, Ji et al (2010) observed a difference in storage carbohydrate accumulation in drought-sensitive and drought tolerant wheat. Interestingly, genotypic variation for WSC accumulation in the stem, mainly fructans, is well established in wheat (Rebetzke et al 2008;Dreccer et al 2009) and consistent with different levels of expression in fructan metabolism enzymes (Xue et al 2008). It is unclear whether a higher level of WSC in stems also extends to more simple sugars in the spike, such as glucose, which have been related with floret fertility, nor what the associated gene expression profile may be.…”

Genomics Approaches to Dissect the Genetic Basis of Drought Resistance in Durum Wheat

“…In bread wheat, QTLs for stem reserve, water-soluble carbohydrates (WSC) remobilization and leaf senescence have been reported across well-watered and waterstressed conditions (Snape et al 2007 ;Rebetzke et al 2008 ;Bennett et al 2012 ;Zhang et al 2015 ). Although these studies showed an important role for WSC in assuring stable yield and grain size, Rebetzke et al ( 2008 ) concluded that the small effects of many independent WSC QTLs may limit their direct use for MAS. A combined QTL analysis for yield of several wheat populations evaluated across different environments and seasons enabled Snape et al ( 2007 ) to identify QTLs showing stable and differential expression across irrigated and non-irrigated conditions.…”