Objectives Breeding wheat with K-high efficiency is an important pathway for alleviating pressure of potash resource shortage in China. In this study, to better understanding the genetic mechanism, the correlated traits of K-efficiency at wheat seedling stage were investigated by different K treatments, and the molecular markers closely related to K-efficiency traits were screened by correlation analyses. The study will provide support for cloning of K efficiency-related genes and breeding of wheat varieties with K-high efficiency.

Methods Using 134 wheat cultivars as materials, a hydroponics experiment with complete random design in triplicate was conducted in greenhouse at Shandong Agricultural University in 2014 and 2015. The seedlings of 7 cm high and 7 days old of all the cultivars were subjected to low K (LK) and normal K (CK) levels for 28 days in the dark, then harvested and divided into shoot and root. The seedling dry weight (biomass) and K content were analyzed, and the K accumulation, dry biomass ratio of root to shoot (RSDW), root to shoot ratio of K accumulation and K use efficiency were calculated. To investigate the effects of low K treatment on biomass and K-efficiency related traits, the correlation analysis of tested traits based on the 15230 different SNP markers was performed using GLM and MLM models in TASSEL 5.0 to obtain stably and significantly correlated markers/locus for wheat seedlings.

Results The contents and accumulation of K in roots, shoots and whole seedlings were all significantly decreased, although the root biomass and the K use efficiencies significantly increased at the seedling stage under the low K treatment. A total of 1300 markers were significantly associated with biomass and K-efficiency related traits, of which, a total of 1102 markers were located on the 19 chromosomes, and most of these molecular markers were screened only under specific K treatment conditions, and three loci including Excalibur_c14273_1407, Ku_c11150_773 and BS00094893_51 were identified under at least three environments. Meanwhile, a total of 4 loci such as wsnp_Ku_c13311_21255428, Excalibur_c8670_972, IACX5989 and wsnp_Ex_c12887_20426781 were confirmed to be significantly associated with six or seven traits.

Conclusions Low K stress significantly influenced the growth of wheat seedlings and the number of related molecular markers. Most of the molecular markers related to K-efficiency and biomass traits are detected only under one environment, indicating that these tested traits might be controlled by different genes. The study also detected four hot sites (molecular markers) which were associated with at least six traits exhibiting a significant correlation with K-efficiency traits at wheat seedling stage. These sites possibly contain important genetic information and deserve to be further investigated.