Genome-wide Association Study For Protein Content In A Large Germplasm Collection Of Chinese Wheat Landraces

The low genetic diversity and narrow genetic basis of wheat,have became one of the focuses of wheat breeding.China's local wheat varieties are rich in genetic variation,strong adaptability and affinity,and the local wheat quality traits in China also have strong regional characteristics.It is an important germplasm resource for breeding improvement.In this study,272 Chinese local wheat varieties plant in seven different environments for three consecutive years were used as materials to determine the protein content.The high-throughput Wheat 660 K chip was used for genetic diversity.The 272 copies of the material were subjected to a whole-genome association analysis based on group results and genetic relationships,combined with the phenotypic data of the protein content determined in this assay.The main research results obtained are as follows:1.Protein content was measured in 272 local wheats grown in 7 different environments(Chongzhou in 2015,Chongzhou in 2016,Mianyang in 2016,Ya'an in 2016,Chongzhou in 2017,Mianyang in 2017,and Ya'an in 2017),The results showed that the average protein content of the Chinese wheat landraces was 13.79% in all testing environments,and 45 wheat varieties with high protein content had an average protein content of more than 15%,18 wheat varieties with low protein content with an average protein content below 12%.There was a very significant positive correlation between protein content in seven different wheat environments in China(r = 0.543–0.705).Analysis of the protein content of landraces from different wheat regions in China(zones VI-NEW,VII-NS,VIII-NWS,X-XJ)showed lower levels of protein content than those areas in China,and the difference is not significant.The protein content of landraces from different wheat growing zones in China(I-NW,II-Y&H,III-YTS,IV-SAS,V-SWAS)was high and the difference was not significant.2.Using the genotypic data obtained from the Wheat 660 chip,a genome-wide association analysis of protein content was performed on 272 Chinese wheat varieties.A total of 46 SNP markers associated with protein content traits were detected(P< 0.0001),18 QTL segments(10 Mb),distributed on chromosomes 2A,2B,3B,5B,5B,6A,6B,7A,7A,7A and 7B.The phenotypic variation contribution rate(R2)ranged from 6.2% to 10.1% for a single association locus.These Markers: AX-94913395 to AX-109853556(2A),AX-111127963(2B),AX-109335297 to AX-109975004(3B),AX-108932412 to AX-110979583(3B),AX-109971694 to AX-110487962(3B),AX-108919027 to AX-111600410(5B),AX-108728520 to AX-111801527(5B),AX-109995708 to AX-111614403(5B),AX-110996588 to AX-111139810(6A),AX-111024271(6A),AX-110914313(6B),AX-111644024(6B),AX-110535435 to AX-110631409(7A),AX-108873894(7A),AX-109883919(7A),AX-109536152(7A),AX-111167265(7A),and AX-89654502 to AX-111539331(7B)can be detected in both environments.The most significant markers are AX-110996588 to AX-111139810,and the phenotype contribution rate is 10.1%.The lowest contribution rates are AX-109971694 to AX-110487962,and the phenotype contribution rate is 6.3%.3.By analyzing the variance of haplotype QTLs of 272 Chinese wheat varieties,44 high-protein and 17 low-protein wheat varieties were identified.It was found that QTL5 and QTL17 were mainly responsible for the control of high proteins,which were located on chromosomes 3B and 7A,respectively.The main control proteins were QTL11 and QTL16,located on chromosomes 6B and 7A,respectively.