Construction Of High-density Genetic Linkage Map And Identification Of QTLs For Drought Tolerance Related Argonomic Traits In Sunflower

Sunflower(Helianthus annuus L), native to North America and north of Mexico,is one of the four major oil crops in the world, and widely cultivated in more than 40 countries.China is the sunflower planting power in the world with more than 400 years cultivation history. Sunflower is mainly cultivated in the arid and semi-arid regions of northwest, north and northeast of China, in which Inner Mongolia has the largest cultivated area and the hightest production. However,the main sunflower planting areas has a serious drought problem because of the insufficient precipitation and uneven temporal and spatial distribution, which has become one of the main factors restricting sunflower yield and quality. And breeding and promotion of drought-resistance varieties is the most economic and long-term way to solve this problem. The construction of high-density genetic linkage map and identification of QTLs for drought tolerance related traits in sunflower laid a solid foundation for the high-efficient drought resistance molecular breeding.Using a single seed descend method, recombinant inbred lines(RILs) of 187 F5 individuals were constructed by the cross between Helianthus annuus K55 with drought sensitive type and K58 with drought-tolerant type. The SSR, SRAP and AFLP molecular markers were used to analyse individual plant, and the phenotypic characteristics of drought resistance related traits were mearsured under two field experiments and two water treatments(normal irrigation and rainfed irrigation), respectively. The main results were as follows:1. The growth of sunflower was significantly affected by drought stress, therefore, the plant became dwarf and the relative chlorophyll content in the leaves declined. The 10drought-resistant related traits, such as total leaf area and water-holding rate, had significantly difference between two water treatments. The 10 traits had highly significantly difference between population materials. The interaction of genotype and the environment reached the extremely significant difference. 2. The correlation analysis of 10 drought resistance related traits showed that the 10 traits, such as total leaf area and water-holding rate, had correlation relationship. Under the drought stress, the 10 traits showed more significant correlation relationship, especially for the correlation relationship between single grain weight and total leaf area, plant height and stem diameter.3. A total of 48 suitble primer combinations were selected from 90 AFLP primers, and used to amplify 187 RILs of sunflower. A total of 1119 loci were amplified, of which 393loci(35.1%) were polymorphic and the average polymorthic information index was0.0321.4. A total of 39 suitble primers were selected from 90 SRAP primers and used to amplify 187 RILs of sunflower. A total of 692 loci were amplified, of which 238 loci(34.6%) were polymorphic and the average polymorthic information index was 0.0247.5. A total of 78 suitble primer pairs were selected from 500 SSR primers, and used to amplify 187 RILs of sunflower. A total of 452 loci were obtained, of which 184 loci(43.1%) were polymorphic and the average polymorthic information index was 0.0092.6. A molecular genetic linkage map of sunflower including 738 markers was contructed using Joinmap 4.0 software, which consisted of 17 linkage groups and had the length of 3543.50 c M, with the average distance between markers of 4.80 c M. Each linkage group had an average of 43.3 markers and an average length of 208.4 c M. Markers randomly distributed on the genetic linkage map, and the Pearson function analysis showed that the correlation coefficient was 0.784 between marker number and linkage group length of each linkage group under the p<0.05 significant level. A total of 225 markers in the linkage map showed segregation distortion, and formed 19 hot spots of segregation distortion.7. The QTLs of 10 sunflower traits under two water treatments, such as SPAD, plant height and stem diameter, were detected using the muti-model method of Map QTL 4.0software, which LOD > 2.5 was used as a critical value for QTL. A total of 30 QTLs for 9traits were observed and distributed in 10 linkage groups, explaining the phenetic variation from 5.7% to 32%, of which 8 QTLs were detected in both two water treatment. A total of17 QTLs were detected under drought stress treatment. The QTLs controlled stem diameter,seed setting rate, water-holding rate and hundred seed weight were only one, respectively.In addition, two QTLs controlled total leaf area, three QTLs controlled plant height, four QTLs controlled leaf number and SPAD value. A total of 13 QTLs were detected under normal irrigation. The traits panel size, water-holding rate, plant height, stem diameter,SPAD and leaf numbers were controlled by 1, 1, 2, 2, 3 and 4 QTLs, respectively.8. A total of 30 QTLs were detected under the two water treatments, of which 7 QTLs showed additive effect, 3 QTLs showed partial dominat effect, 4 QTLs showed dominant effect, and 16 QTLs showed the superdominant effect, accounting for 23.3%, 10%, 14.1%and 53.3% of all the QTLs, respectively.