| Rape is one of main oil crops widely grown in the word, and in our country,it is an important source to the vegetable oil, the largest planting area and the most products. Economic value of the oil is affected by the content of oil and composition of fatty acid in seed either for edible use or for industrial use.The current average of oil content is about 40%, far from the theoretical oil content, and the content of oleic acid and linoleic acid in seed are beneficial to human, but lower. Therefore, Improving the content of rapeseed oil, oleic acid and linoleic acid are the goal on quality improvement of rape at present.Utilizing heterosis is one of the most effective ways to increase yield and improve quality in crops. Rapeseed is one of the most successful crops in heterosis utilization worldwide. heterosis utilization worldwide. To explore the sources of heterosis for agronomic and quality traits in rapeseed, it will play an important role in hybrid breeding. There were more papers about oil content, the oleic acid and linoleic acid in rapeseed had less research and got different results. Research results on oil content in rapeseed from different authors were different, it might be that different materials and different methods they used in their researches. Study further on inheritance system of oil content, oleic acid and linoleic acid, and mapping QTLs linked to them, could enrich the quantitative genetic knowledge about rapedeed.It will play an important role in quality improvement in rapeseed.In this study,6 pure line varieties from different origins were used to produce 30 hybrids by hand pollination within Griffing model I mating design. These hybrids, together with their parents, were tested for oil content in two different locations. Combining ability and heterosis on oil content were analyzed. A six basic generations (PI, P2, F1, B1, B2 and F2) derived from crosses of CG38×B25 in rapeseed (Brassica napus L.) were used to analyze the inheritance of oil content in seed, oleic acid and linoleic acid in oil, applying the mixed model of major gene plus polygene. And the BC1F1 population was used to construct a genetic map in rapeseed(Brassica napus L.), based on RAPD, SSR and SRAP markers. QTLs linked to oil content, oleic acid and linoleic acid were identified in this population.The main results are as follows:1. The results of combining ability analysis on oil content showed there were the extremely significant difference in two locations, the general combining ability(GCA), specific combining ability(SCA), anti-cross-effects of oil content were extremely significant, and all three effects were significantly affected by the environment. The broad-sense heritability of oil content were relatively higher than narrow-sense heritability, and narrow-sense heritability were higher than the difference between broad-sense heritability and narrow-sense heritability, indicating that the contribution of additive effects to phenotype was much higher than non-additive effects. The variance of additive effects on oil content was much higher than of non-additive effects and anti-cross effect. The less variance of interaction with GCA and the environment, the larger of interaction with SCA, anti-cross and the environment, indicated that additive effect was principal for heredity of oil content, GCA in different environments was more stable.2. The results from heterosis analysis of oil content showed that the mid-parent heterosis and the over-parent heterosis between the tested materials were significant different, but the heterosis was relatively lower. There was extremely significant positive correlation with different hybrid in two environments, indicating the heterosis of oil content had a certain stability. T-test on oil content between reciprocal cross showed there were the extremely significant difference from 8 combinations, and the cytoplasmic effect on oil content could not be ignored.3. Correlation analysis of combining ability showed that there were significant positive correlation on GCA and SCA between two environments. The performance of parental GCA was relatively more stable. Correlation analysis showed that there were significant positive correlation between the sum of parent GCAs, SCA and F1, and the correlation of the sum was higher. The correlation between GCA and SCA was not significant. The correlation between the sum of parent GCAs and heterosis on oil content was not significant. But there was extremely significant positive correlation between SCA and heterosis, indicating that SCA and heterosis were induced to non-additive effect of gene.4. The relationship of CG38, a rapeseed line(B. Napus) introduced from Canada, and B25,a artificially resynthesized rapeseed line(B. napus), was much distantly, the difference of oil content and other quality traits were comparatively large. The average oil content of CG38(P1) and B25(P2) was 41.67%,30.02%, and the average content of oleic acid was 57.51%,36.69%, and the average content of linoleic acid was 18.83%,12.98%. The value of oleic acid and linoleic acid was closer between F1 and the lower parent(B25), that of linoleic acid in three segregating generations was closer to the lower parent(B25). In B1, B2 and F2 population, the three quality characteristics were normal distribution, indicating that they are quantitative genetic traits controlled by multiple genes.The oil content was controlled by at least six genes, oleic acid was controlled by at two genes, and linoleic acid was controlled by at least four genes.5. The heredity of oil content, oleic acid and linoleic acid of the cross CG38/B25 was analyzed with major gene plus polygene model, indicating that oil content was controlled by one additive-dominance major gene plus additive-dominance-epistasis polygene(D-O). The heritabilities of major gene were 25.81%～67.26%, and that of polygene was 27.12%～44.77%. Oleic acid and linoleic acid were controlled by two additive-dominance-epistasis major gene plus additive-dominance-epistasis polygene(E-O). For oleic acid, the heritabilities of major gene were 67.69%～86.84%, and that of polygene was 0.03%～9.89%. For linoleic acid, the heritabilities of major gene were 37.22%～66.37%, and that of polygene was 5.96%～26.09%. 6. Using BC1F1 as mapping population, a genetic map in rapeseed (Brassica napes L.) was construct by SSR, RAPD and SRAP marker. It was marked 136 molecular polymorphic site, including 67 markers SRAP,48 SSR and 21 RAPD markers. The genetic map contained 20 linkage groups(LG1-LG20). And the genetic distance was totally 1725.00cM. The average distance between two markers was 15.97cM.7. Two QTLs related to seed oil content were identified with the interval mapping of the software QTL Icimapping v2.2. One QTL was located in the region of SSRRa2-E0-EM15ME14 on linkage group LG10, which could explain 4.43% of the oil content variation in the population and additive effect was 0.42%. The other was located in the region of EM5MEllb-EM12ME14 on LG15, and explained 18.68% phenotypic variation and additive effect was -0.60%.Two QTLs related to oleic acid were identified. One QTL was located in the region of EM12ME17-EM9ME10 on linkage group LG15, which could explain 8.99% of the oleic acid content variation in the population and additive effect was 1.58%. The other was located in the region of AG16-EM17ME15b on LG20, and explained 5.30% phenotypic variation and additive effect was -1.22%. One QTL related to linoleic acid were identified. It was located in the region of EM5MEllb-EM12ME14 on linkage group LG15, which could explain 9.46% of the linoleic acid content variation in the population and additive effect was 0.68%.
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