The Application Of Microspore Culture In Late Bolting Chinese Cabbage

Chinese cabbage is one of the most important vegetable crops with the largest cultivated area and highest yield in China, and in dominant position in vegetable production and supply. However, the problem of bolting before harvest has been restricted the production of spring cabbage and high-latitude and high altitude summer of raw cabbage production in chinese cabbage cultivation. To solve this problem is most economical and effective means is breeding late bolting varieties. Through conventional breeding methods generally need5-8generation to get a stable inbred line, or self-incompatibility system. Meanwhile, spring cabbage resistance to strong bolting, which also increases difficultly to generation of breeding.Through isolated microspore culture for haploid breeding could purify breeding materials rapidly, is an effective way to speed up the process of breeding. Isolated microspore culture could simplify breeding procedures and shorten the breeding cycle,and is widely used in breeding programs. By using this technique, we could get a stable pure line quickly, which is the basis of hybrid breeding. Microspore culture has been reported to be successful in many genotypes of Chinese cabbage, however,embryogenesis in late-bolting varieties has proved difficult. In order to improve embryogenesis frenquency in such genotypes, effects of difficult pretreatment, flowering stage and culture ways on isolated microspore embryogenesis were investigated in22late-bolting varieties of Chinese cabbage. And we observed isolated microspore culture embryogenesis, non-normal plannts The result showed that:1、Embrogenesis frequencies varied remarkably among different varieties.using the conventional methods of isolated microspore culture, the embryoids were induced in only five varieties out of22ones, that is10C2,10C4,10C5.10C21and10C22, the highest embryo yield was3.16embryoids per bud, and embrogenesis frequencies varied remarkably among varieties; It is observed that the embryo frequencies were enhanced in10C7,10C8,10C10and10C18, but weaked in10C2,10C4,10C5,10C21and10C22when the buds pretreated with8%mannitol; The embryo frequencies of10C7,10C12,10C21and10C22were improved by the pretreatment of0.2%n-butano for5h;The embryo frequencies of10C18,10C19,10C21and10C22were increased when pretreated with25%PEG for5h.2、33℃heatshock pretreatment on microspore embryogenesis was essential.33℃heatshock12h treatment could starting higher microspore division, but he final embryoyield was far below the33℃heatshock24h. And without heatshock treatment didn’t induce embryoids.3、Derived buds in the early flowering of Chinese cabbage were obtained the highest number of embryoids, develop the best, followed by the flowering stage. The same material for different flower buds taken isolated microspore culture,embryo yield had significant differences, and reached a significant level. Agitation culture(60r/min)increased the frequency of embryogenesis of Chinese cabbage and the embryos reduces the time2～3d, more favorable embryo induction and formation than the static culture.4、10C18、10C21and10C22out of22late bolting varieties or combination of Chinese cabbage got regenerated plants,and regeneration rates were4.3%,45.7%and39.6%, respectively. Other varieties didn’t obtain regenerated plants.5、Experimental study found that microspore embryogenesis of Chinese cabbage was not synchronized with the development, globular, torpedo, cotyledonary embryoetc. co-existed. Embryoids of bolting chinese cabbage induced abortion phenomenon obviously, embryos remained in a certain stage(especial the globular,heart-shaped embryos) or torpedo-shaped embryos,cotyledonary embryos lack of tip growth point,couldn’t further develop into embryoids. There were non-normal plannts in the regenerated plants,sone of them could regenerate normal palntes after several subcultures culture.6、Late unicellular stage microspores could develped into mature pollen through gametogenesis pathway. Different pretreatments could change the developmental pathway of microspores, turn the pathway from gametogenesis to gametophytic.There existed multi-division paths from microspores culture to embryogenesis.The main way was the division path B. In the study, we observed that the embryogenesis of the cabbage bolting were division path B.