| Peanut(Arachis hypogaea L.)is an important source for edible vegetable oil that widely cultivated around the world. Thus, peanut has drawn more and more attentions to its high yield and high quality. Under the condition of limited planting area and production, increasing oil content is the main breeding goal for modern agriculture. The quality of peanut oil is affected by its fatty acid composition, oleic acid, which is one of the major fatty acids for the peanut oil, has several superior features. While, high content of palmitic acid is harmful to human health. The features make the high oleic acid breeding as a vital breeding goal in peanut. QTL mapping for oil content and fatty acids is an essential theoretical basis for the high oil content and high oleic acid breeding. In this study, a recombinant inbred line population, which derived from the hybrid of a high oil content parent Xuhua13 and a low oil content parent Zhonghua6, has been constructed for the construction of genetic map and QTL mapping for the oil content and fatty acids content in peanut. The following are the major results of this research:1. A total of 848 polymorphic markers between the parents was screened from 9,121 markers. Using the RIL population with 187 lines, a linkage map containing 807 markers was constructed. This map consisted of 20 linkage groups, covering 1639.78 cM, with an average distance of 2.03 cM. The length of linkage groups varied from 29.96 to 133.92 cM, while the average genetic distance was 0.79-4.90 cM. And the number of molecular markers per group was 7-92. Comparing with previously published linkage maps shows a good collinear.2. Phenotypic analysis for the parents and the RIL population in two years: the results indicated that two parents had significant differences in oil content and fatty acids. The contents of oil, stearic acid, oleinic acid and arachidic acid of Xuhua 13 were significantly higher than those of Zhonghua 6, while the content palmic acid and linoleic acid were less than Zhonghua 6. In the RIL population, the variations of all traits were significant between the parents; the range of content distribution tends to a normal distribution as quantitative traits. The stearic acid, linoleic acid, arachidonic acid and tetracosanoic acid have a larger varation range, the coefficient of varation more than 10%, while oil content has a less varation range, the coefficient of varationis 3.82% and 3.10% in two years respectively. Oil content and the content of stearic acid, arachidic acid, arachidonic acid were highly significantly correlated between Oil content and the content of fatty acid compositions, and the others not significantly. Correlation analysis revealed that the content of these major fatty acids were significantly correlated. The correlation of seed oil content and the contents of fatty acid composition was almost same in two years. The Oil content and the contents of fatty acid composition were highly significant difference in different years; there are also highly significant interaction effects between genotype and environment. We obtained one peanut line with high oil and two new germplasms with high oleic and low palmitic by phenotypic analysis.3. QTL mapping on the oil content and oleic acid content was carried out using the SSR genetic map and phenotypic data of 2014 and 2015. We totally detected 26 QTLs by using QTLNetwork, including 17 QTL in 2014 with the individual QTL explaining 6.16%-32.06% of phenotypic variation and 9 QTLs in 2015 with 8.33%-41.96% of phenotypic variation. 7 QTLs could be detected repeatedly in two years, including 2 QTLs for oil content with 9.76%-22.00% of phenotypic variation and 1 QTL for the content of palmitic acid, stearic acid, arachidic acid, arachidonic acid and tetracosanoic acid respectively with 8.73%-41.96% of phenotypic variation. In order to the deeply studies the environmental effects and genotype and environment interaction effects, a total of 21 QTLs was detected in the two years and distributed on 8 linkage groups, A05, A08, B01, B03, B04, B05, B08 and B10. We detected one pair of epistatic QTLs in oleic and linoleic acids respectively, only two sites in the interaction, and the interaction of the same sites. The qOCA08 affect oil content through regulating arachidic acid, but qOCB03 could be detected for oil content by both conditional and unconditional QTL mapping methods. The QTLs could be used for molecular assisted selection.4. By analyzing distribution of the QTLs on the linkage groups, we found that QTLs for different traits was distributed on the same region. In this study, we detected five marker intervals, and each of them associated with two or more traits. The results showed that the different triats QTL have same or different effect directional in same marker interval. Such as AGGS1639-AHGS1795 on B10 was related to palmic acid, oleic acid and linoleic acid, qPAB10 and qLAB10 have negative additive effect, while qOAB10 has positive additive effect. AGGS1383-TC1E7 on A08 was related to stearic acid, arachidic acid, arachidonic acid. Significantly difference between oil content and fatty acid composition was detected, and the same linkage group of the same or adjacent region different traits QTL was gathered together. The study indicated that, the traits phenotypic correlation may have originated from QTL loci related to control the quantitative traits. |
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