| Wheat（Triticum aestivum L.）is one of the most important grain crop.Drought stress has affected the development of agriculture in China and even the world since ancient times.Synthetic hexaploid wheat（SHW）possesses numerous genes for drought that can help breeding for drought-tolerant wheat varieties.We evaluated 10root traits at seedling stage in the F9 recombinant inbred lines derived from an F2population of a SHW line and a common wheat line,namely SW population,under normal（NC）and polyethylene glycol-simulated drought stress conditions（DC）by using the method of water treatment.We used SPSS to do Pearson correlation analysis and principal component analysis and mapped quantitative trait loci（QTL）for root traits using an enriched high-density genetic map which has been constructed.We proposed a lot of putative candidate genes by searching of public databases.The main results are described as follows:1、All 10 root traits were selected for Pearson correlation analysis to identify relationships among them.We found 68 significant（P<0.05）or highly significant correlation coefficients（P<0.01）,under NC and DC.Here eight of ten root traits have significant（P<0.05）or highly significant correlation（P<0.01）between each other.2、All root traits were subjected to principal component analysis.Three principal components identified with eigenvalues>1 accounted for 88.79%of the total variation in all traits under NC.In DC,three principal components identified with eigenvalues>1 accounted for 86.58%of the total variation in all traits.3、Using subordinate function value method to calculate the D value of SW population,and evalulate the ability of drought-tolerance by D value.There are 26lines with D value greater than or equal to 0.5,and 15 lines with D value less than 0.3.The D value of SHW-L1 and Chuanmai32 was 0.88 and 0.49,respectively.We found top 10 genotypes with extremely high and low tolerance about drougt,and the maximum and minimum of them is 0.79,and 0.16,respectively.4、With four replicates per treatment,we identified 19 QTL for root traits under NC and DC,and 12 of them could be consistently detected with three or four replicates.Two novel QTL for root diameter and root fresh weight under NC explained 15.7 and 9%of the phenotypic variation respectively,namely QRD.sicau-2B and QRFW.sicau-5D,and six novel QTL for root fresh weight,total root surface area,number of root forks,number of root tips and the ratio of root water loss under DC explained 8.5-14%of the phenotypic variation,namely QDCRFW.sicau-2B、QDCTSAR.sicau-2B、QDCRF.sicau-2D、QDCRT.sicau-3D、QDCRWL.sicau-5A and QDCRFW.sicau-7D.Here seven of eight novel QTL could be consistently detected with more than three replicates.5、We used novel QTL to identify a total of seven putative candidate genes within10,000 bp upstream and 10,000 bp downstream of the corresponding position.After searching of their functions,three candidate genes,underlined QDCRT.sicau-3D and QDCRF.sicau-2D,namely Traes CS3D02G069000,Traes CS3D02G069100,and Traes CS2D02G447800,which might participate in the interaction between the root and the biochemical basis for wheat tolerance to drought-stress were predicted. |
