| Radish (Raphanus sativus L.), classified in the Brassicaceae family, is an important root vegetable which was originated from China. In recent years, the requirement of radish quality and production is more and more with the raise of people's living standard. So that, it is essential to innovate radish germplasms.Microspore culture and autotetraploid induction were the important methods for radish germplasms innovation. So far, the microspore culture of radish was restricted by the genotypes. The efficient embryo induction and plantlets regeneration system were still not established. Besides, the induction and identification system of autotetraploid radish were imperfect. So that in the study, the factors which influenced embryo induction rate and plantlet regeneration rate were researched in the study of microspore culture, while the autotetraploid induction method was improved and the characteristics between diploid and autotetraploid radish were compared, which aimed to improve the system of microspore culture and autotetraploid induction with identification, formulate new varieties and provide technique support for microspore culture and autotetraploid induction of radish.In the study of radish microspore culture, the genotypes with the ability of forming embryos were selected from the accessions kept in Vegetable institute. We improved the induction rate of embryos and the regeneration rate of plantlets by researching the factors which influenced embryo formation and differentiation, respectively. In our study,14 genotypes obtained embryos and there were significant differences among different varieties in embryo yield. From the microspore cytological observation, we found that the numbers of microspores at the uninucleate stage were most when the length of buds was between 2.5 mm to 3.5 mm. It could improve the embryo yield for some genotypes in the addition of 1-2 mg/L AgNO3 or 0.05 mg/L 6-BA. The addition of 0.1 g/L AC in culture medium was beneficial for the embryo quality. Cotyledon-shaped embryos could develop into plantlets on the MS medium with 0.2mg/L 6-BA and 0.02mg/L NAA directly. "MS-3+4 mg/L AgNO3+0.2 mg/L TDZ+0.5 mg/L 6-BA+0.2 mg/L NAA" can form secondary embryos, which could differentiate to plantlets. The most suitable root-induced culture medium was:B5+3% sursose+0.7% agar+0.1 mg/L NAA. In the study of autotetroploid radish induction, the autotetroploid induction rate of different DMSO concentrations with 0.1% colchicine was compared. Besides, the morphological and cytological characteristics were compared between diploid and tetraploid radish. The results showed that Nau-dqt, Nau-qtbjq and Nau-dy13 got tetraploid, Nau-qtbjq got the highest tetraploid yield and 0.1% colchicine with 0.2% DMSO induced the most autotetraploid radish. Compared to the diploid radish, autotetraploids grew slowly on the seedling stage and had leaf shrinkage and late florescence. Besides, the autotetraploid had wider petal, larger pollen, more chloroplasts numbers in the guard cells and lower stomata density than diploid radish, which were significant. The observation of meiosis of pollen mother cells in diploid and tetraploid radish indicated that the latter existed unusual stages with some frequencies, such as twi-nucleoluses in prophaseⅠ, chromosomes outside metaphase plate in metaphaseⅠorⅡ, lagged chromosomes in anaphaseⅠand asymmetric division of chromosomes in anaphaseⅡ, which may be the reason for the low pollen germination rate as we speculated. |
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