Genetics And Bionomics Analysis And Heterosis Utilization On Oil Content In Brassica Napus

High-oil-content breeding is a primary improvement strategy for oil-yield in oil crops, and it's an essential goal in Brassica napus in China as well. In this study, our objectives and strategies are summarized as following.1. To detect maternal effects on oil content of self- and cross-pollinated seeds using 3 high-, 1 medium- and 2 low oil content materials in Brassica napus;2. To perform genetic analysis on oil content in Brassica napus with 8X8 complete diallel cross design using 1 high-, 5 medium- and 2-low oil content materials;3. To study systematically the basis of bionomics on oil content in Brassica napus using 386 accessions at four different ecological regions during four annual rounds.4. To investigate heterosis and general compatibility among 4 high-, 5 medium- and 2 low oil content materials in Brassica napus;5. To explore effects of chemical hybridization agent WH-1 on genic male sterility and its initialization on heterosis in Brassica napus.The results are harvested and shown as following.1. Oil content of hybrid in Brassica napus is regulated by maternal genotype with effect value at 0.86. Xenia was observed on oil content of hybrid with xenia effect at 0.14, and the average share percentage is 1.86.2. Genetic pattern of oil content fits to additive-dominant-epistasis model, and the additive, dominant and epistasis effects are significant. About 70% phenotypic variation on oil content was due to additive and dominant effects. There was also a small amount of epistatic effects. The broad and narrow sense heritability of oil content was 83.88% and 36.94%, respectively, and cytoplasm is playing positive or negative roles on oil content.3. The oil content of seeds on middle of main inflorescence is much higher than that of seeds on both ends, while the upper is even better than the bottom. The oil content on primary branches could be sorted as following: 1st >2nd >3rd >…, while little difference was observed on the upper 3rd to 4th branches, whereas significant difference was detectable between the first and last branches.4. Oil content of spring rapeseed is much higher than that of winter cultivars. Along the Yangtze River, regions could be ranked according to the oil content as: downstream >middle >upstream, but Yellow River >Yangtze River. Seven stable high oil content accessions have been picked out.5. Significant difference was observed between different trials in an ecological region. Along Yangtze River and Yellow River, plants showed high oil content with more than 42% are suitable for growth in Guangyuan, Shuangliu, Mianxian, Jiujiang, Xiangbei, Yichang, Tongling, Hangzhou, quanjiao, Shanghai, Hefei, Xinyang and Chengxian. Rapeseed productivity would be increased and economic benefits could be enhanced in these regions from high oil content cultivars in Brassica napus.6. The oil content capacity of hybrid F₁ was controlled by parents. High positive heterosis on oil content was observed in hybrids from low oil-content parents, but the absolute oil content is still low. Negative heterosis of F₁ from parents with obvious difference on oil content was detectable. Minor positive heterosis of hybrid on oil content was detected from parents both with medium oil content, but it's very hard to pick out expected crosses with high oil content. Though minor heterosis on oil content in hybrids from both high oil content parents was observed, over-parent cross could be generated from these crosses.7. The optimum concentration of chemical WH-1, which could induce male sterility, is 0.1⁰.2 mg/ml for the first spraying and 0.05⁰.1 mg/ml for the second processing. The first operation was carried out at young-flower-bud stage (before Chinese Spring Festival in Wuhan), after 20 days, the second round was performed at 3⁴ ml per plant without any chemical damage. At full- and eventual flowering stages, pollen activity was detected, and 98% plants were male sterile, 95% plants were pure hybrids confirmed with SSR. Based on results of heterosis utilization, we can draw a conclusion that high oil content parents treated with chemically-induced male sterile regents could generate high oil content hybrids in Brassica napus.