Allotriploid Chromosome Inheritance And Progeny Karyotype Analysis

Triploids play an important role in the formation of polyploids and the evolution of species.There are few studies on the fate of triploid offspring and meiotic behavior.In this research,allotriploid rapes(AAC)were used as materials to identify chromosomes accurately.Triploids were found to have a certain fertility.On the one hand,triploids can be doubled to generate hexaploid spontaneously at a very low rate.And the hexaploid genome is unstable.On the other hand,allotriploid rapes can produce a small amount of seed,then self-progeny as well as individual chromosome number can be increased with generations,tending to become tetraploid.In addition,the first and second generation individuals are mainly aneuploidy.Using the precise chromosome identification technique we established for the rape to observe the chromosome pairing in metaphase I(MI)and chromosome segregation in anaphase I(AI).It was found that the chromosome of A-genome were mostly in the form of bivalents aswell as the chromosome of C-genome mostly existed in univalent form in the middle of meiosis,and there was also a high proportion of chromosome pairing abnormalities,such as the formations of partial homologous chromosomes and the formations of multivalents.At anaphase I,the chromosome of A-genome is usually balanced to daughter cells.However,the chromosome of C-genome which can't be paired at metaphase I are randomly distributed to the daughter cells.This phenomenon led to different proportions of chromosomes existing in cells at AI.The same observation was done on the chromosomes of the first filial generation,the increase of C-genome chromosomes was found.The C-genome chromosome which has homologous chromosome can be paired and isolated as A-genome chromosome in this generation.In addition,the pollen activity was found to be improved by generation.Through this study,we observed the chromosome composition and meiotic behaviors of allotriploids and their progeny.It is meaningful to understand the role of allotriploids in polyploid formation and species evolution.