Induced Variation Of Chinese Cabbage By EMS Treatment

Germplasm resources are the foundation of crop varietal improvement. The scarcity of germplasm resources is the most serious problem in Chinese cabbage breeding, the creation of breeding materials with rich genetic basis is the emphasis of research for breeding scientists. Natural mutation ratio can be improved more than a thousand times by artificially inducing variation, which makes it possible to create and screen orientation variation. The direction of artificial mutagenesis is uncertainty, and most of mutants are recessive. Combined artificial mutagenesis and microspore culture together, we can get homozygous genes rapidly and reduce the time used for mutations identification.In this experiment, different genotypes of Chinese cabbage were used as materials , the methods of seed mutagenesis,bud mutation combined with microspore culture, isolated microspore mutation and culture and pollen mutagenesis were investigated by EMS inducing. The suitable EMS concentration and processing time of different treatment methods were determined. The variation in related physiological and biochemical characteristics on the defense system in seeds and seedlings after dealing with seeds were discussed. Furthermore, The morphological identification and molecular profiling were conducted in offsprings of buds pollination selfing and free microspore culturing, resulting in some types of mutation materials. The main research results are as follows:1. Using Chinese cabbage genotypes'99-2'and'Jinyu 80', the effects of 4h seed-treatment with different EMS concentration solutions on several major characteristics such as seeds germination, seeds conductivity and the activity of SOD, POD and MDA in seeds and seedlings of Chinese cabbage were studied in the present paper. The results showed that EMS concentrations ranged from 0-0.1%, with EMS concentration increasing, seed germination potential, seed germination rate and seedling surviving rate gradually decreased, the root tip and cotyledon edge of seedlings became brown gradually. The conductivity of seeds and the MDA content of seeds and seedlings were both increased with EMS concentration increasing. The SOD, POD activity of seeds and seedlings was promoted by low EMS concentration solution treatment and inhibited by high EMS concentration solution treatment. The optimal EMS concentrations inducing Chinese cabbage seeds mutations ranged from 0.4% to 0.6%.2. Using buds of Chinese cabbage '85-1' as materials,the effects of different EMS concentrations on the rate of microspore swollen and the condition of embryos alive and regeneration were studied. The results showed that with EMS concentration and treatment time increasing, both the rate of microspore swollen and embryonic generation reduced gradually, and the number of deformity embryos increased. Treating buds by 0.1% EMS for 15min or 30min, we can get quite some energetic embryos which can be regenerated into seedlings as normal, with a high variation ratio. But if the EMS concentration was reached 1%, with treatment time of 15min, only a few activity embryos were produced with a low regeneration ratio and without seedlings at all.3. mutagenesis microspore of three inbred lines in vitro induced by EMS then cultibated , In the process of the microspore culture , though cytology observation, we can get the result that the rate of microspore expands is significantly reduced along with the increase of concentration and the extension of mutagenesis time, nothing embryos was got at last。4. Pollens of two different varieties of Chinese cabbage were treated with EMS-paraffin oil solution, half lethal EMS concentration and treatment time of pollen germination in vitro were studied. The result showed that the germination rate of pollen stored in liquid paraffin oil was not affected within 1h, and then was decreased with prolonged storage. With the increasing EMS concentration or the mutagenesis time gradually, the rate of pollen germination reduced. The suitable EMS concentration induced for pollen mutagenesis was 0.015%,with treatment time of 45~60min.5. By routine identification and molecular appraisal, sdifferent types of mutants from mutagenesis offsprings were screened.After the seeds mutagenesis, there was no significant differences in traits variation in M1 generation, but some mutants can be observed in M2 generation. There were large differences in phenotypic variation among the plants obtained from microspore culture of pollens mutagenesis and buds mutagenesis, with multiple mutant types.