| Oilseed rape is one of the world’s four major oil crops and is widely planted in China and around the world. In the flowering, rapeseed petals can absorb and reflect almost two-thirds of photosynthetic active radiation; the growth and development of petals will consume a lot of energy; petal is also an important medium for the spread of diseases such as Sclerotinia. Apetalous trait can increase the efficiency of solar energy utilization, reduce energy consumption and avoid disease by morphological. It is an important way to improve the rapeseed yield and enhance disease resistance by cultivating apetalous rapeseed.In this study, a recombinant inbred lines (RIL) population in Brassica napus L. consisting of 198 lines was constructed by single seed descend method. This population that now is F2:8 generation was deriving from hybrid combination between apetalous rapeseed APL01 and petalous rapeseed Holly. Based on two years of petal degree data, the quantitative traits genetic analysis in three generations of P1, P2 and RIL population was conducted, the genetic parameters was to be estimated. A high density genetic linkage map of Brassica napus was constructed by SNP and SSR markers. QTLs for apetalous were fine identified based on three years of petal degree data. Taked apetalous gene expression levels as a quantitative trait and used traditional QTL analysis methods to identifiy its eQTL. The main results were as follows:1. Genetic analysis of apetalous in Brassica napusThe major gene and polygene mixed genetic model was used to analyze the P1, P2 and RIL population of rapeseed cross between apetalous line APLO1 and petal one Holly. Results showed that the genetic model of apetalous trait was fitted for MX2-Additive-A, which was two additive effect major genes and additive polygene model. The additive and epistasis effect of major genes were -8.78 and -21.03 respectively, the additive effect of polygene was -27.08; all the three effect values were negative, which means reducing the petal degree. The heritability value of the major genes reached to 85.38%, which significantly higher than that of the polygene, indicated that the heritability of major genes accounted for the major part of the genetic system in apetalous. There was little difference on effects and heritability between the two years.2. Construction of genetic linkage mapA Brasscica napus genetic linkage map including 65 SSR markers and 3698 SNP markers was constructed by using MSTMap software. This map covered 5065.16cM and contained 37 linkage groups. The average length of linkage group was 136.90cM and the average distance between markers was 1,35cM.3. QTLs fine Mapping of apetalousAccording to three years of petal degree data,10 QTLs for rapeseed apetalous were detected by using WinQTLCartographer2.5 software through the composite interval mapping. qAPA9a, qAPC8a and qAPC8b explaining phenotypic variation ranged 6.26% to 42.08% were located on A9a, C8a and C8b at 2012. qAPA3b, qAPA9a-1, qAPA9a-2 and qAPC8b explaining phenotypic variation ranged 4.75% to 10.62% were located on A3b, A9a and C8b at 2013. qAPA3a, qAPC8a and qAPC8b explaining phenotypic variation ranged 5.31% to 52.60% were located on A3a, C8a and C8b at 2014.The QTL with the same position and similar effect on the linkage group C8a and C8b were repeat detected in two years and three years trials respectively. qAPA9a was also repeat detected in two years trials. However, qAPA3a, qAPA3b and qAPA9a-2 were detected only in a single year trial.The variation of marker interval was from 0.48cM to 2.67cM in 10 QTLs. The marker interval of qAPC8a and qAPC8b were 1.92 cM and 2.24 cM respectively.That basically matched with the requirements of 1-5cM confidence interval for fine mapping. The distance of QTLs and nearest marker were all less than 1cM; the distance of other QTLs and nearest marker were all less than 0.1 cM beside qAPC8a; the distance of qAPA3a and nearest marker was only 0.01cM.4. eQTL mapping of apetalous geneDetected relative expression level of apetalous gene BnFLA in the RIL population through fluorescence quantitative PCR and taked the relative expression level as a special phenotypic data. As a result, three eQTL related FLA was identified on A2 with a phenotypic variation from 10.94% to 25.60%. eqAPA2-1 explaining phenotypic variation of 13.08% was located on 18.31cM of linkage group A2; eqAPA2-2 explaining phenotypic variation of 10.94% was located on 194.11cM; eqAPA2-3 explaining phenotypic variation of 25.60% was located on 202.51cM. The phenotypic variation of three eQTL was greater than 10%, therefore they were three main effect QTLs, and the additive effect of eQTL were positive, therefore the apetalous alleles from normal petalous parent Holly. |
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