Creation Of Autopolyploidy Germplasm Of Brassica Rapa, Brassica Oleracea And Brassica Nigra

Inducing plant polyploids artificially is one of important ways of generating new germplasms ornew materials. Polyploids can be directly applicated in breeding new varieties, and also can be used asintermedium parents to overcome incompatibility during hybridization between different species orgenus. In our current study, we treated the seedling apex of Chinese cabbage, cabbage and Brassicanigra with different concentrations of cochicine solutions. Then the plants polyploidy level wasidentified by means of cell DNA relative content measurement, morphological observation,chromosome number examination, and karyotype analysis. Besides, we also investigated theirmorphological characters, meiotic behavior, nutritional quality and DNA methylation. The main resultsare showed as follows:1. By improving the treating methods of cochicine solutions, new tetraploid and octploidgermplasms of Chinese cabbage, cabbage and Brassica nigra were produced successfully, in whichrates of plants with doubled chromosomes were over80%.2. By cytological examination and karyotype analysis, the chromosome number in the root tip cellsof tetraploid Chinese cabbage, cabbage and Brassica nigra was2n=4x=40,2n=4x=36and2n=4x=32,including four genomes, respectively. By mensuration with flow cytometry, relative DNA contents incells of tetraploid Chinese cabbage, cabbage and Brassica nigra were twice folds of those of their owndiploid plants.3. Meiotic process was relatively normal in the tetraploid Chinese cabbage, cabbage and Brassicanigra, and their pollen viability was ranged from70.85%to82.35%, respectively. However, the meiosisof octploids was quite abnormal, wothout normal pollen grains.4. The tetraploid Chinese cabbage, cabbage and Brassica nigra had stronger growth potential, andcontents of soluble sugar, vitamin C, crude protein, and water were higher than of their own diploids,respectively.5. DNA methylation between diploid and tetraploid of Chinese cabbage, cabbage and Brassicanigra was analized. The results showed that the total methylated ratios of tetraploid were increased.Compared with level and pattern of DNA methylation in diploid and tetraploid, there was significantlydifference in Chinese cabbage, cabbage and Brassica nigra. These changes may be expressed inphenotype as epigenetic by controlling the expression of certain genes.