Chromosomal Inheritance And Progeny Analysis Of A Novel Synthetic Hexaploid Allopolyploid Brassica

Polyploidization is widespread in nature and it is a prominent force in the evolution of higher plants.Polyploidization usually leads to the immediate formation of new species,increases biodiversity and provides new genetic materials.Although the polyploidic genome has been extensively studied,the mechanism of chromosomal stability at the beginning of polyploid is unclear.In this thesis,using five tandem repeats(5S rDNA,45S rDNA,CentBrl,CentBr2,pBrSTR)and two BAC clones(KBrH092N24 and BNIH 123L05)as the mixed probes for FISH,all chromosomes of synthesized hexaploid Brassica(S0)and self progenies(S1)could be identified accurately.In order to understand the genetic characteristics and stability of hexaploid Brassica,the mitosis and meiosis chromosomes of synthesized hexaploid Brassica were used as materials for FISH.The main results are as fellowing:(1)It has been proved that chromosomes of So are doubled successfully with whole set of chromosomes of parents.The chromosomal behaviors of So at meiotic metaphase I and anaphase I were found abnormal to some extent.The specific performance:a)In addition to bi-valents,there are a lot of multivalents and univalents at M I observed with significent different frequences among different chromosomes;b)in-accurate separation and early separation of chromosomes exist during A I.By statistical analysis,we found that there are hot and cold spots in chromosomal instability(dislocation)among chromosomes from both A and C genome,and the errors of chromosomal pairing(univalents and multivalents)at M I have negative impact the accurate separation of the chromosomes at A I.(2)In generation Si,a large number of aneuploids(29 strains,90.62%)and three euploids are dentified by karyotyping analyses.Besides,there are some chromosomal rearrangements.According to this study,the synthesized hexaploid Brassica were cytogenetic analyses and the results improves our understanding the variation of genome structure and genetic stability of polyploidization.The individuals screened with stable chromosomes could be used as future polyploid breeding.