QTL Analysis For Height Of Main Stem And Number Of Branches In Peanut(Arachis Hypogaea L.)

Peanut(Arachis hypogaea L.) is an important source of vegetable oil and protein. It has rather high potential value in nutrient, economic and medical effect. Due to that cultivated peanut is a strictly self-pollinated crop and an allotetraploid with a large and complex genome, the genomic research in this crop has little progressed. The trait associated with plant architecture in peanut(Arachis hypogaea L.) is complex quantitative trait affected by many factors which is closely linked with yield and quality. It is also a morphology index for indentification on germplasm resources. Therefore,it is crucial for peanut varietal improvement by breeding of the ideal plant type in peanut. It is basis of molecular marker-assisted breeding that conduct the work of genetic research for plant type and QTL mapping.In the present study, a genetic map was constructed based on SSR markers by using the RIL generation of “zhonghua10× ICG12625” as the mapping population. We investigated three yield related traits for two years of the F6 and F7 generations, including height of main stem, number of total branches and number of branches with pods. All of these three traits related yield were mapped with QTL. The main results are as follows. 1. Genetic Analysis for Height of Main Stem and Number of BranchesBased on the statistical analysis of the data of yield related traits of F6 and F7 generations of RIL population, height of main stem, number of total branches and number of branches with pod of these three traits showed a continuous and rich variation. All the three traits fit the normal distribution, show the characteristics of quantitative traits. Transgressive segregation for all the traits was observed in RIL population at different environment. Using the mixed major gene plus polygene inheritance model, we perform the genetic analysis for height of main stem and number of branches. The results show that: The best fitting genetic are all two major genes plus polygene both in height of main stem and number of branches. 2. Genetic mappingBy using the RIL population and SSR markers, we constructed a linkage map consisting of 20 linkage groups which contained 656 markers. The genetic map covered 1165.45 cM and the length of each linkage group varies from 29.96 cM ~106.87 cM. The average length of each linkage group is 58.27 cM and the average number of marks is 32.8, with an average distance of 1.78 cM. The marker density of this genetic map has good colinearity with previously published genome map of peanut. Segregation distortion of molecular markers were in cluster of tightly loci. Both of these markers were distorted to the female parent. 3.QTL Analysis for Height of Main Stem and Number of BranchesBy using composite interval mapping method, we performed QTL mapping and analysis of genetic effects.42 QTLs were indentified in all the three traits and the QTLs were located on 12 chromosomes with contribution ratio from 3.69% to 13.04% in two years. Contribution ratio of 6 QTLs which has the main effect is greater than 10%. All the QTLs for the number of branches with pod showed positive additive effect, while the number of total branches and the height of main stem had 3 and 5 QTLs showed positive additive effect. We found the QTL hotspots that QTL were in cluster of tightly linked loci on the linkage map. Most of the QTLs were located in Lg9(6)?Lg14(7)?Lg15(5)?Lg16(6)linkage group. We also found that a number of QTLs are in the same range on the linkage map such as qMHA02.2 and qBPA02.1 are in the same interval of the linkage group AGGS2511~AGGS2388. The result is consistent with correlation analysis on these traits. We identified 3 repeated QTLs for height of main stem, qMHA04.1?qMHB04.1 and qMHB04.2, while no repeated QTLs are detected related to the number of branches. The QTLs with stable and large contribution rate can be used for marker-assisted selection and the next fine-mapping studies.