Genome-wide association study of traits related to low potassium tolerance in common wheat

Objectives Screening markers associated with low potassium (K) tolerance in wheat will lay a foundation for revealing the genetic mechanism of low K tolerance in wheat.

Methods Total of 198 wheat cultivars were collected from the wheat planting area in southern of Huang-Huai River plain. After germination of seeds, the wheat seedings were cultured in normal K nutrition solution for 4 days, then transferred into low (0.01 mmol/L) and normal (2 mmol/L) K solution for 25 days. The biomass and K contents of wheat shoots and roots were measured. The values of 7 traits were calculated. The genome-wide association study (GWAS) was analyzed with 35K single nucleotide polymorphism (SNP) chips by mixed linear model (MLM). The candidate genes and superior alleles were screened with associated SNP loci.

Results Of the seven low-K-tolerance traits, the K accumulation of shoot, root and total plant and the K accumulation ratio of root to shoot declined significantly, while the K utilization index of shoot, root and total plant increased significantly under low K stress condition. The population materials were divided into two subgroups based on structure analysis and PCA analysis. GWAS analysis revealed that 75 SNP loci were distributed on 16 chromosomes (P < 0.001), except 1A, 3B, 3D, 4D and 6A chromosomes. There were 13 available candidate genes screened out, which might associate significantly with the seven low-K-tolerance related traits in the regions from the positions of SNP, 14 superior alleles were obtained and 6 superior alleles had higher frequency in the tested population.

Conclusions Seven low-K-tolerance related traits fitted the feature of quantitative character with coefficient variation ranged from 20.66% to 30.44%. 40% of SNP markers distribute on 2B, 5B and 6B chromosomes. 21 SNP loci were associated significantly with more than 2 low-K-tolerance related traits. The phenotypic contribution explained by single marker loci varied from 5.78% to 11.22%. TraesCS4A02G335400, TraesCS2B02G306000 and TraesCS5B02G260000 may be involved in material transportation process; TraesCS1D02G350600 and TraesCSU02G105300 may involved in stress response; TraesCS2A02G000200 may regulate the signal transduction in environmental stress.