| Chinese Cabbage (Brassica campestris ssp.pekinensis) is an important kind of vegetable originated from our country. The germplasm resources of Chinese cabbage are abundant all over the country. Intensive traditional breeding has been carried out on the parent line inbreeding and selection. Although the achievements were significant, it is laborious and time-consuming. It takes 5-7 years and even more to breed a stable and excellent self-cross line successfully.Microspore culture has become increasingly attractive by the reason of its great potentiality for double haploid production. It takes only 1-2 years to obtain homozygous lines as parent plants, and the time is shortened greatly compared to conventional breeding methods.In this study seven genotypes of Chinese cabbage, HY, KF, BL, SZ, ZX, QP and QX, were used in the investigation of genotypical effects on isolated microspore culture. The main results are as follows:1 Genotypic screening: Different frequencies of embryos were obtained among 4 genotypes (HY, KF, BL and SZ), while no embryo was obtained from ZX, QX and QP. HY with a highest yield produced 12.32 times as many embryos as SZ with a lowest yield.2 Analysis of factors affecting isolated microspore culture of Chinese cabbage: The effects of the activated charcoal on embryo production was investigated. For most of genotypes, the embryo production increased in the media supplemented with O.lmg/ml activated charcoal. The number of embryos for KF and BL rised from 1.25 to 17.08 and 0.67 to 14.58 on average, with-13.67 and 21.76 times compared with the control for KF and BL respectively. No obvious enhancive effect was observed on HY, with the yield of embryos 3.42 in the treatment and 3.17 in the control.3 Embryogenesis was affected by different concentrations of sucrose. It was necessary to optimize the concentrations of sucrose in the media for different genotypes. As for KF, a higher yield of embryos was obtained when the microspore was induced first in the medium NLN-16 for 48h, and then transferred toNLN-13.4 It is not clear for microspores to be treated in vitro with 50mg/l colchicines for 48h followed by a culture in the same kind of medium but without colchicines to induce embryos formation. The effect of colchicines on chromosome doubling showed that only HY gets 3 embryos and without regenerated plants and that it is impossible to know the result of chromosome doubling.5 During the process of tissue culture, vitrification of the plantlets frequently happened. Properly increasing the agar content in the medium could abate the vitrification. Among the three media with agar of 0.8%, 1.2% and 1.6%, MS with 1.2% agar could both decrease the number of vitrified embryos and increase the rate of living transplants.6 The ploidy level of microspore-derived plants was determined by flow cytometrv. about 56.4% of spontaneous doubling and 43.6% of haploid were observed from regenerated plants in the process of tissue culture.7 Among the three reduplication methods, the ratio of diploid varied from zero to 40%. Forty percent of double haploid was obtained from the treatment of dipping roots of haploid plant in colchicines solutions. Chromosome doubling reached 35% when applying colchicines solutions on the meristem. Direct applying colchicines into the media cultured microspores only got 3 enbryos, unable to get the result of chromosome doubling.8 Primary RAPD analysis was carried out with primer S51, S344 and SI31 screened out from 80 random primers to detect the polymorphism of regenerated plants. The result of RAPD with S344 showed that the similarity coefficients among 19 plants derived from microspores varied from 0.16 to 1.00, with an average of 0.58. This indicated the genetic background varied among different regenerated plants. This result further confirmed that the regenerated plants developed from not the somatic tissue but different microspores. At the same time, in the base of the polymorphism with primer S51, S344 and SI34 the RAP...
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