Study On Germplasm Creation Of Brassica Napus And Genetic Analysis Of Plant-type Characters

Rapeseed is one of the major oil crops in the world, which is a kinds of Brassica plant in Cruciferous. It is not only important source of edible oil and protein feed, but also is one of major industrial raw materials. At present, Brassica napus is cultivated widely in China instead of Brassica campestris and Brassica juncea. Thus, weak and narrow genetic foundation of Brassica napus with short history of cultivation in China seriously limited the breeding of Brassica napus. However, on the other hand, abundant genetic resources within Brassica are helpful for creation of germplasm of Brassica napus. Therefore, interspecific hybrids in Brassica are important and efficient method to build and broaden Brassica napus germplasm resources, and discover some helpful genes which can improve quality and yield of rapeseed. This is also one of main research directions of genetics and breeding for rapeseed researcher. Allotriploid were artificially synthesized by culture of immature embryos from interspecific hybridization between Brassica juncea and Brassica oleracea, and the derived lines were identified at cytology, morphology and molecular level. At last, it was used to genetic analysis at the aspect of plant heights and pod lengths for Brassica napus. new germplasm and semi-dwarf10D130(A+A+C+C+), which formed by partly exchange of genome both Brassica juncea (AjAjBjBj) and Brassica oleracea (C°C°). The results are as follows:1. Interspecific hybridization between15Brassica juncea and6Brassica oleracea were got,30d later, the numbers of residual ovary and immature embryo were recorded, the results showed that there were obviously different number of ovary residual and active immature embryos per100buds in different crosses, and the numbers of immature embryos from positive and negative cross were compared, the results showed that Brassica juncea as female help to improve the probability of immature embryo.2.43true hybrids were confirmed by identification of and chromosome number among184kinds of hybrid clones. Vegetative of true hybrids showed strong growth advantage, and apparent morphology was more close to the Brassica napus. These triploid hybrids were divided into three types according to floral organ morphology and pollen fertility, including the highly sterile (no powder, pollen contamination rate was0%), less powder (pollen efficiency was5.35%-12.00%) and fine powder (pollen efficiency was25.3%-47.87%), respectively. Seeds from different kinds of hybrids were recorded at harvest periods, the results found most of seeds were empty or semi-full, and seed setting rate change from0to3.65%. In addition, a plant doubled chromosome was got with full anther, and developed2-4seeds per pod.3. Chromosome numbers among20clones were surveyed, the results found8clones had27chromosomes and9clones had27-34chromosomes, respectively, and others clones could hardly be determined number of chromosome because of great changes among different cell. This indicated that the unequal divisions and chromosome doubling happened during mitosis of some cells. By observing the process of meiosis, the results show that the majority of pollen mother cells early joint abnormalities, mostly formed univalents and some bivalents; due to segregation distortion, chromosomes serious backward during meiosis anaphase Ⅰ and anaphase Ⅱ. For plants of Chromosome doubling, some cells remain chromosome lag during late Ⅰ, anaphase Ⅱ, but the rate and number of lagging chromosomes were less than allotriploid.4. Brassica napus (A+A+C+C+) were artificially synthesized by systematic selection and breeding of Hybrids between Brassica juncea (04K220) and Brassica napus (04K04). The study showed that the interspecific hybrids (So) selfed to get clones (S1) by rescue of immature embryo, and seed setting rate improved from generation to next generation. Through continuous selection and breeding from2005to2012, there were122descendant lines whose morphologies were similar to be Brassica napus.78of122descendant lines and the two parents conducted PCR amplification by37 polymorphic efficient SSR primers, the results showed that the expansion of144with37pairs of primers, each primer pair amplified by an average of3.89, of which124were polymorphic, accounting for86.1%; comparing with the male parent (04K04) and female parent (04K22),34bands increase and9bands missing among124bands, which accounted for27.42%and7.26%of the amplified polymorphic bands, respectively. cluster analysis among two parents and78lines showed that genetic material from the interspecific hybrid happen great loss and rearrangement during the multi-generation breeding process. Genetic similarity coefficient of78hybrid derivative lines varies between0.65-1.00. When the similarity coefficient is0.72, all hybrid derivative lines and parents can be divided into four groups.5. Plant heights and pod lengths and their components of78derived lines were surveyed, the results showed that some of derived lines were lower50-60cm plant height, lower mycobacterium site, more branches, shorter pod length than those of normal rapeseed in Chongqing. The oil content, glucosinolate and erucic acid content of78lines were skimmed by using near infrared, in which oil content of4derived lines higher than45%, the glucosinolates content3of them is less than35umol.g, erucic acid content of23lines is less than1%and that2of them lines is higher than55%.6.10D130is a kind of new and semi-dwarf germplasm with yellow seed coat and high oil contents, which was artificially synthesized to Brassica napus.(A+A+C+C+). average plant height of10D130is162cm in the rapeseed planting areas of Chongqing, which decreased by54cm comparing with conventional elite cultivars of Zhongshuang11. Its branch height, length of main inflorescence, main stem length and valid branch space reduced39.46%,14.8%,22.49%,18.86%comparing with Zhongshuang11, respectively, and numbers of its valid branch rose28.59over Zhongshuang11. These traits above mentioned were significant difference (P<0.05). Six generations (P1, P2, F1, F2, B1, and B2) were produced from a cross between semi-dwarf10D130and Zhongshuang11(ZS11) to analyze inheritances of plant height and related characteristics by the mixed major gene plus polygene inheritance model. The results showed that the plant height, branch height, length of main inflorescence and valid branch space of10D130×ZS11were dominated by a pair of major gene with additive-dominant effects plus polygenes with additive-dominance-epistasis effects (D-0model). The first valid branch space of10D130×ZS11was dominated by two pairs of major gene with additive-dominant-epistasis effects plus polygenes with additive-dominance-epistasis (E-1model). The branch height, length of main inflorescence, valid branch space and number of valid branch were significantly and positively correlated with plant height. Therefore, judged from traits, genetic sources and genetic models,10D130is a different new germplasm with semi-dwarf comparing with previous research.7. Genetic models of silique body length (SBL), valid silique length (SL) and beak length (BL) were studied in the cross of Zhongshuangll(P1)×10D130(P2), in which difference between P1with long-silique variety and P2with short-silique line is significant (P<0.05). SBL, SL and BL of six populations (P1, P2, F1, F2, B1and B2) were analyzed by joint segregation analysis. The frequency distributions of the F2, BCP1and B2generation exhibited to have multi-modal patterns, indicating the influence of major genes mixed with polygenes. To test and disclose the genetic bases of SBL, SL and BL, the most suitable genetic models were selected among twenty-three genetic models established about three silique traits. The results showed that SBL was well described by E-0model, a case of two additive-dominant-epistasis major gene as well as additive-dominant-epistasis polygenes,. and SL was controlled by two additive-dominant-epistasis major gene as well as additive-dominant polygene (E-1model). In addition, BL was controlled by two additive major genes as well as additive-dominance polygene (E-3). In addition, it is a few little genetic variations of silique body length (SBL), valid silique length (SL) and beak length (BL) caused by environmental factors so as to select and breed in the early generations.