The Stability And The Behaviour Of Chromosomes Discuss Of The Artificially Synthesized Allopolypliod Brassica

Brassica juncea?AABB?,B.rapa?AA?and B.nigra?BB?are the important species of the U-triangle,which contain different excellent characters for trait improvements of the crops of Brassica.In order to compound those advantaged traits to one species,synthesized hexaploid could be made by inter-specific hybridization.Little known about the chromosome stability and heredity was reported for synthesized hexaploid of Brassica.In this thesis,we synthesized two different genotypes of hexaploids?A^j A^jA^rA^rB^j B^j and A^jA^jB^jB^jBⁿBⁿ?.Using a toolkit developed by our lab to precise identify each chromosome of Brassica,and combining with two-step multi-color FISH,the karyotypes,chromosome stability and meiotic chromosomal behaviors were analyzed in three generations of the hexaploids.The main results are as following:?1?A total of 99 individuals?including S₁,S₂ and S₃?from two re-synthesized hexaploid were analyzed and we found that with the increasing of the generations,the tendency of the chromosome number were decreased and the ratio of aneuploidy were increased.Beside,in the same genotype the hexaploid plants formed by different parents were different in the chromosome and genome stability.?2?Different types of abnormal chromosomal pairing and missegregations were found at meiotic metaphase I and anaphase I,respectively,in S₁ generation in hexaploid A^jA^jA^r A^rB^jB^j,The genetic stability of each chromosomes were analyzed during the first meiosis.These results suggested that meiotic abnormalities are the main causes of genomic instability of resynthesized hexaploid.?3?The phenotype of resynthesized hexaploid are different among the individuals formed by different parents and it changed persistently with increase of generations.According to this study,we preliminarily understand the chromosomal stability and heredity of synthesized hexaploid.The individuals with complete set chromosomes were selected,which is expected to be useful in rapeseed breeding.Meanwhile it is helpful to broaden the germplasm resources of Brassica.