Objectives Crops are found response genetically to potassium (K) nutrition, so the identification and localization of the molecular markers, that are stable and significantly correlated to traits of yield and K efficiency under different K nutrition levels, will provide reference for further genetic modification of related traits and genes cloning in breeding.
Methods A group of 134 wheat varieties (or lines) were used in a two-years field experiment, in which applying K (T1) and not applying K (T2) were setup. The yield and K efficiency related traits of wheat were measured, and the average data of traits were calculated under 6 defined environments, as the respective average values of each treatment in one year and two years. Genome-wide association analysis was carried out for the tested traits using SNP molecular markers.
Results Compared with K application treatment, the K use efficiencies were significantly higher, while the K contents and accumulation of individual plant and the total spikelet number were significantly lower under no K application treatment. The coefficients of variation of the traits were 6.98%–350.38% among the group of cultivars (lines), and 14 of traits had heritability of > 50%, with the highest trait of plant height (92.03%). According to genome-wide association analysis on the 7485 SNPs with satisfactory diversity, a total of 1420 molecular marker sites were identified associating with 23 traits significantly (P ≤ 0.001), and located in 21 chromosomes. There were 1097 (77.25%) molecular marker sites detected in only one environment, and 323 molecular marker sites that could be stably identified in at least 2 environments, and 113 of them were related to K efficiency, e.g. the molecular marker sites Tdurum_contig26281_139 and Kukri_c307_2053 could upregulate the absorption of K, Ex_c19038_571 and BS00039148_51 could increase K use efficiency. There were 22 molecular marker sites that could be identified in at least 4 environments, which were related to 5 traits such as plant height, 1000-grain weight (1000-GW) and grain number per spike. Among the 22 molecular marker sites, RFL_Contig 4069_2628 and BS00003632_51 were related to plant height and 1000-GW, and were extremely stable and could be detected in all the 6 environments. The expression of genes in the two molecular marker sites significantly affected the variation of plant height and 1000-GW, with average contribution rate of 9.59% and 13.66%.
Conclusions Under different K nutrition levels, the molecular markers that are closely correlated to the yield and K efficiency traits, are detected in different sites. About 77.25% of the molecular marker sites are detected only in specific environments. However, 22 significantly correlated molecular marker sites (involving 9 traits related to yield and K efficiency) can be detected in at least 4 environments (6 environments in total), forming high-frequency expression molecular marker sites. Among them, two molecular marker sites are stably correlated with plant height and 1000-GW in all environments. The regulation effects of related genes on related traits of these molecular marker sites are less affected by K treatments, which has high theoretical and applied value and is worthy of in-depth study.
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