Genome-wide Association Study For Black Point Resistance In A Large Germplasm Collection Of Chinese Wheat Landraces

Wheat(Triticum aestivum L.)is one of the major cereal crops with wide adaptability,which belongs to the genus Triticum L.of Gramineae family.Black point of wheat is a worldwide wheat disease,it can significantly downgraded wheat processing and nutrition quality,inhibited wheat germination and seedling growth.In this study,717 Chinese wheat landraces and 163 Chinese wheat cultivars were evaluated for wheat black point and accessions with high black point resistance were selected.Landraces were grown across four environments in China and cultivars were grown across two environments in China.Black point test of harvest-ripe grain were used to calculate a black point rate(BPR)for each accession at each site.The 717 wheat landraces were genotyped using the DArT-seq genotyping-by-sequencing(GBS)platform.Out of the 717 landraces 272 that represent genetic diversity,were selected and genotyped using the Axiom? Wheat660 SNP array.Genome wide association studies(GWAS)for black point was carried out by genotypic and phenotypic.A collection of 717 wheat landraces were grown across four environments in China and 163 wheat cultivars were grown across two environments in China,which black point tested of harvest-ripe grain was used to calculate a black point rate(BPR)for each accession at each site.Sixty-one wheat landraces and eight wheat cultivars were screened out to be resistant to black point disease.It was found that the black point rate of Chinese wheat landraces was lower than the wheat cultivars,and the average black point rate was 15.60%,it can provide germplasm resources for modern breeding to improve black point resistance.Seven wheat landraces and six wheat cultivars were screened out,which Shumai 969,Fanmai 3,Guangtoumai(AS661763),Zhongxinmai 98,AS661463,Lunzao 987,Zhengmai98 had stable resistance.However,environmental factors,such as annual rainfall,annual accumulated temperature and annual average sunshine,significantly affected the resistance of wheat landraces black point disease.The black point rate of wheat landraces from Middle and Low Yangtze Valleys Autumn-Sown Spring Wheat Zone(III-YTS)andSouthwestern Autumn-Sown Spring Wheat Zone(IV-SAS)is the lowest,and they have the better resistance of black point disease.However,the black point rate of wheat landraces from the Northwestern Spring Wheat Zone(VIII-NWS)is the highest,the resistance of black point disease is poor.Genome-wide association studies(GWAS)using 9,740 DArT-seq and 178,803 SNP markers detected fifteen quantitative trait loci(QTL),including 9 DArT-seq and45 Wheat660 K SNP markers.They are located on chromosomes 1B(5),2A(23),3A(4),5A(2),5B(4),6A(2),6B(2),6D(8),7A(2)and 7B(2),respectively.It can explain 2.60-17.49% of phenotypic variances.