Characterization Of Genes Related To Grain Traits In Aegilops Tauschii

Aegilops tauschii also known as coarse grass goats, belong to the family of the Gramineae wheat grass goats, is one of the ancestors of hexaploid common wheat, wheat D genome donor. It has some desirable characters such as high tillering ability, good fecundity, high protein content and excellent resistance to powdery mildew, stripe rust and stem rust, as well as to tolerance to low temperature and Preharvest sprouting; is the important genetic resource for the improvement of bread wheat with valuable gene resources.To identify the quantitative trait loci (QTLs) responsible for grain size and shape variation in Aegilops tauschii, seven parameters (grain weight, grain length, grain width, grain aspect ratio, the perimeter of grain, grain thickness, grain surface area) related to grain size and shape were measured using Smart Grain digital image software.2012-2013,2013-2014 grain length is mainly concentrated in between 4-5mm; grain width in 2012-2013 and 2013-2014 is slightly different segments, grain width ranged between 1.5-2.5 mm, Correlation analysis in natural populations, some important traits such as grain weight and graining size, grain surface area were tested significant positive correlation. Especially,2013 grain width had positively correlated with 2013 TKW,2013area, and 2013 W/L ratio with estimate of r=0.621, r=0.859 and r=0.783.Here we show the results of a genome-wide association study based on genotyping 10K SNP variants across 366 diverse accessions Aegilops tauschii collected from 17 countries that were systematically phenotyped for these agronomic traits of seed. Sixteen SNP markers associated with eight grain traits on 5 of the 7 chromosomes (except 1D and 4D) were identified. For TKW, GL, GW and GA respectively three, one, two, ten. The identified QTLs significantly contributed to the variation in grain size and shape. The largest SNP markers clusters, consisting of up to nine SNP markers associated with GA. were found on chromosomes 7D and the one (AT5D4284) marker was on the chromosome 5D; While only one SNP marker for grain weight was found on chromosome 6D; The other two SNP markers for grain weight were found on 2D and 3D; The two markers for grain width were detected on the 2D and 7D;By comparison with the previous discovery sites associated with grain QTL in common wheat. The QTLs (Xcfd70, Xgwm645) for grain length identified by Keith Williams were mapped in the similar locations of the marker (AT6D5664) on chromosomes 3D. Only SNP maker AT2D0981 detected in this study was in a similar position to the QTLs for grain width on chromosome 2D identified by Flavio Breseghello, Yuki Okamoto. Studies on grain size/shape genes in rice, have reported that the GS3 locus was identified to have major effects on grain length and weight and smaller effects on grain width. The DNA of TaGS3 gene was cloned on chromosome 7DS by a comparative genomics approach. The marker AT7D6040 was closed to the gene GS3. The TaGS1a-CAPS marker on chromosome 6D have been previously reported, the TaGS1a gene had functions for grain size traits, including thousand grain weight (TKW), grain length (KL), grain width (KW), grain height (KH), KL/KW ratio (KLW) and grain area (KA) during maturity stage. This gene was located about 110cm from centromere of chromosomes 6DS.The marker AT6D5664 was also identified on chromosome 6D and was 104 cm from centromere of chromosomes. So maybe the marker AT6D5664 detected in this study was in a similar position to the gene on chromosome 6DS identified by Ying Guo et al.We analyzed grain traits using 314 recombinant inbred lines (RILs), which was generated from the cross between moderate dormancy dormant material AS75 and weak material AL8-78.The results showed that most of the inter-grain traits exhibited significant or highly significant correlation. Especially, grain weight had positively correlated with grain length and grain width with estimate of r=0.93, r=0.90. Secondly, grain weight had correlated with grain perimeter and grain surface area with estimate of r=0.84, r=0.80. Lay the foundation for wheat genetic research and molecular marker-assisted breeding and provide a reference. This study provides a fundamental resource for wheat genetics research and breeding, it demonstrates that an approach integrating genome sequencing and GWAS can be used as a powerful complementary strategy.Based on the genetic map (A genetic map comprising 6739 SNP markers was generated.) and phenotypic data, quantitative trait loci (QTL) were mapped for these agronomic traits. A total of 2 putative QTLs were identified for the eight traits. Of the QTLs detected,1 for grain length was identified on chromosomes 5D, phenotypic contribution rate of 7.5%,1 for grain weight was identified on chromosomes 3D.Phenotypic contribution rate of 6.4%.