Genome-Wide Association of Stem Carbohydrate Accumulation and Remobilization during Grain Growth in Bread Wheat (Triticum aestivum L.) in Mediterranean Environments.

Fernando P Guerra,Alejandro Del Pozo,Alejandra Yáñez,Iván Matus

doi:10.3390/plants10030539

Abstract

Water deficit represents an important challenge for wheat production in many regions of the world. Accumulation and remobilization of water-soluble carbohydrates (WSCs) in stems are part of the physiological responses regulated by plants to cope with water stress and, in turn, determine grain yield (GY). The genetic mechanisms underlying the variation in WSC are only partially understood. In this study, we aimed to identify Single Nucleotide Polymorphism (SNP) markers that account for variation in a suite of WSC and GY, evaluated in 225 cultivars and advanced lines of spring wheat. These genotypes were established in two sites in the Mediterranean region of Central Chile, under water-limited and full irrigation conditions, and assessed in two growing seasons, namely anthesis and maturity growth periods. A genome-wide association study (GWAS) was performed by using 3243 SNP markers. Genetic variance accounted for 5 to 52% of phenotypic variation of the assessed traits. A rapid linkage disequilibrium decay was observed across chromosomes (r2 ≤ 0.2 at 2.52 kbp). Marker-trait association tests identified 96 SNPs related to stem weight (SW), WSCs, and GY, among other traits, at the different sites, growing seasons, and growth periods. The percentage of SNPs that were part of the gene-coding regions was 34%. Most of these genes are involved in the defensive response to drought and biotic stress. A complimentary analysis detected significant effects of different haplotypes on WSC and SW, in anthesis and maturity. Our results evidence both genetic and environmental influence on WSC dynamics in spring wheat. At the same time, they provide a series of markers suitable for supporting assisted selection approaches and functional characterization of genes.

Highlights

Bread wheat (Triticum aestivum L.) is one of the world’s most important cereal crops in terms of cultivated area and economic activity [1]
Large differences in grain yield (GY) were observed between both sites, with an average of 3140 ± 550 and 9820 ± 970 kg ha−1 at Cauquenes and Santa Rosa, respectively (Figure 1a)
The opposite pattern was observed for Stem weights at anthesis (SWa), WSCa, and apparent WSC remobilization (ARWSC) (Figure 1b–f), indicating an increase in these traits in response to a lower water availability

Summary

Introduction

Bread wheat (Triticum aestivum L.) is one of the world’s most important cereal crops in terms of cultivated area and economic activity [1]. It is expected that global demand for bread wheat will increase by 70%, by 2050, in line with the projected growth in world population [2]. In Mediterranean-climate regions, temperate cereals like wheat are usually exposed to a severe water deficit during the grain filling period, the so-called terminal droughtstress [6,7,8,9]. This water deficit leads to reductions in canopy photosynthesis, as well as lower levels of assimilate transfer to the grain, leading to smaller kernel weights and GY [7,10]

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