QTL Mapping For Heading Date,Plant Height And Number Of Tillers Of Coix

Coix lacryma-jobi L.is a relative of maize,which belongs to the Maydeae.Coix has rich nutritional value,it is not only a traditional medicine and food plant,but also a new forage crop.Nowadays,the demand of coix is increasing,but the yield is unsatisfactory,so there is a shortage of supply.The yield and quality of coix were mainly restricted by late heading,high stem and ineffective tillers,therefore the study about heading date,plant height and number of tillers,plays an important role in the breeding of coix with high yield and high quality.In this study,we create an F₂ population by cross DHS and XBK.The phenotypic data of plant height,heading date,and number of tillers were collected in several environments.Then we predict the locus of candidate genes based on the results of QTL-mapping and QTL-seq.The mainly results were as follows:1.Plant height,heading date and number of tillers of F₂ population changed within a certain range,and the distribution was continuous,which close to the unimodal or bimodal normal distribution,showing the typical quantitative trait genetic characteristics.The correlation analysis results of F₂ population between different phenotypes showed that there was an extremely significant positive correlation between heading date and plant height（P<0.01）,and the correlation coefficient was 0.420.There also was an extremely significant positive correlation between plant height and number of tillers（P<0.01）,with a correlation coefficient of 0.428.However,there is no correlation between heading date and number of tillers.2.A total of 17 QTLs were detected by QTL-mapping.There were 7 heading date QTLs,distributed on pseudo chromosomes 1,3,8 and 10,which could explain the phenotypic variation of 1.95-8.22%.The 4 plant height QTLs distributed on pseudo chromosomes 1,5,8 and 10,which could explain the phenotypic variation of 3.24%to10.57%.The 6 number of tillers QTLs distributed on pseudo chromosomes 1,3,4,8and 10,which could explain the phenotypic variation of 1.27%to 30.72%.The locus of heading date q HD-10,and the locus of number of tillerss q TN-10 were both detected in two environments.q HD-1-4 and q TN-1,q HD-10 and q PH-10,q HD-8,q PH-8 and q TN-8 were located between the same two markers,respectively.3.Seven candidate regions were obtained by combining SNP-index and In Del-index association analysis,including 2 heading date locus,2 plant height locus and 3number of tillers locus.The heading date locus located at pseudo chromosome 1 and10,at 39.50-47.48Mb and 0-6.06Mb,with 237 and 175 genes,respectively.The plant height locus located at pseudo chromosome 1 and 10,at 38.94-51.17Mb and 0-1.37Mb,with 330 and 35 genes,respectively.The number of tillers locus located at pseudo chromosome 2 at 8.50-12.71Mb with 240 genes,and pseudo chromosome 9,at 77.05-77.23Mb and 77.45-81.15Mb,with 2 and 31 genes,respectively.4.We integrated data of QTL-mapping and QTL-seq,there was an overlap interval of 39.50-47.48Mb of pseudo chromosome 1 related to heading date.Collinear alignment of the 237 genes contained in the overlap interval related to the heeding date of coix with sorghum and maize,it was found that the maize flowering gene glk45（Zm EHD1）could be aligned with EVM0023765,which distributed on the pseudo chromosome 1.EVM0023765 might be a candidate gene for coix heading date.