Genome-Wide Association Mapping of Seedling Biomass and Root Traits Under Different Water Conditions in Wheat

Abstract

Drought is a major threat to global wheat production. In this study, an association panel containing 200 Chinese wheat germplasms was used for genome-wide association studies (GWASs) of genetic loci associated with eight root and seedling biomass traits under normal water and osmotic stress conditions. The following traits were investigated in wheat seedlings at the four-leaf stage: root length (RL), root number (RN), root fresh weight (RFW), root dry weight (RDW), shoot fresh weight (SFW), shoot dry weight (SDW), total fresh weight (TFW), and total dry weight (TDW). A total of 323 and 286 SNPs were detected under two water environments, respectively. Some of these SNPs were near known loci for root traits. Eleven SNPs on chromosomes 1B, 2B, 4B, and 2D had pleiotropic effects on multiple traits under different water conditions. Further analysis indicated that several genes located inside the 4 Mb LD block on each side of these 11 SNPs were known to be associated with plant growth and development and thus may be candidate genes for these loci. Results from this study increased our understanding of the genetic architecture of root and seedling biomass traits under different water conditions and will facilitate the development of varieties with better drought tolerance.

Keywords: GWAS; osmotic stress; root traits; seedling biomass; wheat.

Figure 1

Correlation analyses between eight root and seedling biomass traits for each environment. Trait abbreviations: RLD, root length in drought environment; RLN, root length in controlled environment; RND, root number in drought environment; RNN, root number in controlled environment; RDWN, root dry weight in controlled environment; RDWD, root dry weight in dry environment; RFWN, root fresh weight in controlled environment; RFWD, root fresh weight in dry environment; SFWN, shoot fresh weight in controlled environment; SFWD, shoot fresh weight in dry environment; SDWN, shoot dry weight in controlled environment; SDWD, shoot dry weight in drought environment; TFWN, total fresh weight in controlled environment; TFWD, total fresh weight in drought environment; TDWN, total dry weight in controlled environment; TDWD, total dry weight in drought environment.

Figure 2

Manhattan plots for the eight root and seedling biomass traits identified by genome-wide association study (GWAS) using BLUP values. The dashed line represents the significance threshold (–log10 P = 3.0). Trait abbreviations: RLD, root length in drought environment; RLN, root length in controlled environment; RND, root number in drought environment; RNN, root number in controlled environment; RDWN, root dry weight in controlled environment; RDWD, root dry weight in dry environment; RFWN, root fresh weight in controlled environment; RFWD, root fresh weight in dry environment; SFWN, shoot fresh weight in controlled environment; SFWD, shoot fresh weight in dry environment; SDWN, shoot dry weight in controlled environment; SDWD, shoot dry weight in drought environment; TFWN, total fresh weight in controlled environment; TFWD, total fresh weight in drought environment; TDWN, total dry weight in controlled environment; TDWD, total dry weight in drought environment.

Figure 3

Comparison of the allele effects of four environmentally stable SNPs on chromosomes 2D, 4D, and 6D. Trait abbreviations: TFWN, total fresh weight in controlled environment; SFWN, shoot fresh weight in controlled environment; RNN, root number in controlled environment; SDWD, shoot dry weight in drought environment. ***p < 0.001.