| Drought is so far the most important abiotic stress factor affecting global wheat yield.Development of drought resistance germplasm and the closely linked makers with droughtresistance will become increasingly important for breeding drought tolerant varieties andmarker assisted selection. The objectives of this study are both to screen new droughtresistance germplasm and to detect QTL for drought related traits based on a population of91recombinant inbred lines under normal water (NW) and osmotic stress (OS) treatment.Twenty four drought related traits were investigated at seedling stage, including shootheight, maximum root length, leaf length, leaf width, leaf area, shoot fresh weight, rootfresh weight, total fresh weight, root/shoot fresh weight, shoot dry weight, root dry weight,total dry weight and root/shoot dry weight, etc. The main results were as follows:1. Twenty four morphological and physiological traits related to drought resistance werestudied under NW and OS. There were highly significant differences between23traits,apart from MDA content. The biggest coefficient of variability (CV) was root freshweight (26.24%) under NW treatment and Pro content (42.08%) under OS,respectively. The CV of seven traits were less than10%. These results showed thatthere were relatively abundant genetic variation and great potential for selection in theRIL population.2. RIL population drought resistance was evaluated by principal component andclustering analyses, and all the lines were divided into three groups according to theirdrought resistance: poor drought resistance type (39lines), intermediate droughtresistance type (39lines) and high drought resistance type (15lines). The lines withthe best drought resistance were75,30,45,43,41,27,16,31,71,19,28,92,47,5and42. These lines can be used as new drought resistance germplasm in breeding droughttolerant varieties.3. Nine hundred and thirty-three markers (65SSR and868DArT) were used to constructa genetic linkage map, and these makers covered total length of1351.9cM in wheatgenome, with average distance of1.4cM between adjacent makers. Of these,294makers were assigned to3B chromosome, with average distance of0.5cM betweenmakers. Only three makers were assigned to6D chromosome, and none of the makerswith known chromosome locations was mapped to chromosome5D.4. A total of49QTL were detected for22traits exclusive of RWC and root number under two water regimes. They were located on chromosomes1A,2B,3A,3B,4A,4B,5B,6B,7B and7D, respectively, with10.63%~28.66%of phenotypic variationexplaination. Six QTL out of23detected under NW were major-effect QTL for leafarea, shoot fresh weight, root fresh weight, total fresh weight, root/shoot fresh weightand root dry weight, explaining21.44%~26.59%of the phenotypic variations.However,26QTL were just detected under OS, and four of them were major QTL forshoot dry weight, total dry weight, root/shoot dry weight and MDA content,contributing the phenotypic variations from21.57%to28.66%.5. One QTL cluster for seedling drought related traits was found on chromosomes3B,4A,4B and7B, respectively. Twenty QTL were mapped on chromosome3B for leafwidth, leaf area, shoot fresh weight, root fresh weight, total fresh weight, shoot dryweight, root dry weight, total dry weight, root/shoot dry weight, chlorophyll a/b andMDA content, and10QTL were detected on4B for shoot height, shoot fresh weight,total fresh weight, shoot dry weight, root dry weight, total dry weight and carotenoidcontent.6. The QTL for three drought related traits were detected in the same or near makerintervals under two conditions. Such as Qsh-4B-2.NW and Qsh-4B.OS for SH werelocated on wPt7569-wPt6209of chromosome4B. Qmrl-7B.NW and Qmrl-7B-1.OSwere identified for maximum root length on near wPt0215-wPt2737of chromosome7B. Qmda-3B.NW and Qmda-3B-2.OS closely linked with MDA content were locatedon near maker intervals wPt0855-wPt10071. |
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