| Rapeseed is an important oil crop and economic crop in China. China is the the biggest rapeseed planting country and the largest producer in the world. The year sown area surpasses 7 million hectares, the annual production of rapeseed amounts to 11 milliom tons, and either the planting area or the output occupies 1/3 of the world (Zhou and Fu, 2007). Therefore it is significant to using biotechnologies to raise the breeding level and improve the main traits of rapeseed, such as yield, quality and disease resistance.Brassica napus is an often cross-pollinated polyploid crop. There are possibly genetic variations in varieties which were breeded with traditional selecting. Microspore culture is an important biotechnology which was firstly reported successed in Brassica napus in the 1980s (Litcher, 1982). Homozygous materials could be obtained by using this method. It is significant for improving varieties to study the genetic variations of DH populations which were constructed from different varieties by using microspore culture.Sclerotinia stem rot is one of the most devastating diseases of rapeseed in China, and it is mainly occurred in the Yangtze River basin. It has been reported that Sclerotinia stem rot can cause up to 80% yield loss on rapeseed in severe incidences in China. There are a lot of researches about Sclerotinia stem rot's occurrence, regularity of epidemic and forecast forecast, and some progresses have acquired to prevent the disease by medicament and agricultural cultivation. But it still hadn't changed severely impair condition of Sclerotinia stem rot. Therefore breeding and application of S. Sclerotiorum resistant cultivar was regarded as the most ecomomic and efficiecy way to resolve the problem.In this research, three doubled haploid (DH) populations were generated from three B. napus polima cytoplasmic male sterility (pol CMS) restorers "ZS4R", "7-5" and "P24". And another "650" DH population included 144 DH lines was also used. Main agronomic traits and quality traits of "7-5", "P24" and "650" DH populations were evaluated to explore genetic variation regularity of descendant of microspore culture. On the other hand, "ZS4R", "7-5", "P24" and "650" DH populations were used to select Sclerotinia stem rot resistant DH restorer lines. Main results of the study are as follows:1. By application of microspore culture, "ZS4R", "7-5" and "P24" DH populations consisting of 101, 356 and 421 DH lines, respectively, were generated.2. There are abundant variation among all the agronomic traits and quality traits in the 7-5, P24 and 650 DH populations.3. There is no significant difference among the coefficient of variation of same trait in the 7-5, P24 and 650 DH populations.4. The silique length and glucosinolate content are distorted segregation. Segregation distortion may indicate that preferential gametic selection occurred during the development of the DH lines.5. The results of assessment of seedling resistance to Sclerotinia stem rot showed that the average Sclerotinia stem rot resistance of the four DH populations is distorted segregation. The average resistance of "ZS4R", "7-5" and "P24" DH populations is better than the donors, and the average resistance of "650" DH population lean to the higher resistant parent.6. Correlation coefficient of seedling stage resistance to adult stage resistance is very low.7. Ten elite DH lines with partial resistance to Sclerotinia stem rot were chosen within three years' selection and have been used in hybrid breeding.This study revealed that there is abundant genetic variation in DH populations generated from the varieties (lines) breeded by traditional methods and it is efficient to do the selecting in the DH populations. |
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