| Wheat is an important staple grain crop,and the realization of green production of wheat is of great significance to ensure the security of food and ecological environment in China.Wheat could be affected by various factors from sowing to harvest,among which potassium is one of the important factors affecting the normal growth,development and yield of wheat.Studying the mechanisms of potassium absorption and utilization of wheat and cultivating potassium efficient wheat varieties are one of the important ways to alleviate the shortage of potash fertilizer resources and realize green sustainable development in agricultural production.In this study,437 wheat varieties with different characteristics were used as experimental materials.Field experiments were conducted in Yangling of Shaanxi Province,Luoyang and Nanyang of Henan Province,Suqian of Jiangsu Province for two years（2018-2020）.An augmented randomized complete block was employed.Four potassium efficiency indexes,wheat grain potassium utilization efficiency（GKUE）,Shoot potassium utilization efficiency（SKUE）,potassium harvest index（KHI）and potassium uptake efficiency（KUPE）,were measured and calculated.The relationships between the four potassium efficiency indexes,yield and grain potassium content were analyzed,and the effects of different release years,plant height and awn type on wheat potassium efficiency traits were analyzed.Combined with 660K SNP microarray genotyping data,genome-wide association analysis（GWAS）of wheat potassium efficiency traits was carried out,and the significant association sites controlling wheat potassium efficiency traits were accurately located.Key candidate genes controlling wheat potassium efficiency were screened.The results are as follows:1.There were significant genotypic differences in GKUE,SKUE,KHI and KUPE among 437 wheat varieties.The ranges of GKUE,SKUE,KHI and KUPE in the 8 growing environments were 5.04 kg·kg-1-110.44 kg·kg-1,44.92 kg·kg-1-243.36 kg·kg-1,0.02-0.38,0.03 kg·kg-1-1.64 kg·kg-1;There was a significant positive correlation between wheat yield and GKUE,KHI,KUPE.There was a significant negative correlation between SKUE and wheat yield.2.With the advance of release years,GKUE,KHI and KUPE increased significantly,GKUE,KHI and KUPE of modern wheat varieties were significantly higher than those of historical varieties,SKUE decreased significantly with the advance of release years,and SKUE of historical varieties was higher than that of modern varieties.There were significant linear relationships between the four potassium efficiency traits and plant height.GKUE,KHI and KUPE decreased with the increase of plant height,while SKUE increased with the increase of plant height.Keeping plant height in a suitable range during breeding is beneficial to improve the GKUE,KHI and KUPE of wheat.Breeding the wheat cultivars with or without awn does not affect the GKUE,SKUE and KHI of wheat,but the retention of awn is beneficial for the improving of KUPE of wheat.3.A total of 163 SNP loci were significantly associated with 4 wheat potassium efficiency traits,of which 36 for GKUE,2 for SKUE,44 for KHI and 61 for KUPE were detected.The SNPs were distributed on 21 chromosomes,and formed 138 QTL regions.Among them,10 QTL（QTL7,QTL12,QTL13,QTL31,QTL52,QTL69,QTL78,QTL96,QTL101 and QTL108）intervals were associated with 2 or more traits,and they were distributed on the chromosomes 1A,1B,2D,3B,5A,5B and 6B.QTL96 and QTL101 were simultaneously mapped to three traits.4.A total of 199 candidate genes that may affect wheat potassium efficiency were identified,including two WRKY（Traes CS1A02G264300,Traes CS1B02G374900）,one MYB（Traes CS1B02G374300）and one MADS-box（Traes CS1B02G374700）transcription factors.The genes also included 4 cytochrome P450 genes,8 F-box protein family genes,18 leucine-rich repeat receptor-like protein kinase family（LRR）genes,1 ABC transporter gene,1 zinc finger protein related gene,3receptor-like protein kinase related genes,2 E3 ubiquitin ligase genes and 4 BTB/POZ domain protein genes.In conclusion,there were significant genotypic differences of potassium use efficiency among different wheat varieties,and the increase of wheat GKUE,KHI and KUPE was beneficial to the increase of yield;compared with historical varieties,modern wheat varieties had higher GKUE,KHI,KUPE and lower SKUE;properly reducing plant height was beneficial to improve wheat potassium efficiency during breeding,and retaining wheat awn could increase wheat KUPE.A total of 163 SNP loci were identified on the 21 pairs of chromosomes,including 1A（461.63-462.10 c M）,1B（329.23-329.96 c M,608.53-614.29 c M）,2D（86.49-87.84 c M）,3B（740.08-742.66 c M）,5A（456.08-457.95 c M）,5B（482.41-482.52c M）and 6B（239.74-243.36 c M,374.22-375.52 c M,714.43-717.92 c M）,which are the key areas for the study of wheat potassium efficiency traits.199 genes may be involved in the regulation of wheat potassium efficiency traits,of which 44 are key candidate genes. |
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