Molecular And Cytogenetic Analyses At Meiosis Between A And C Chromosomes In Allotriploid Brassica Hybrids(ACC) Between B.napus(AACC) And B.oleracea(CC)

Success of interspecific hybridization relies mostly on the adequate similarity between the implicated genomes to ensure synapsis, pairing and recombination between appropriate chromosomes during meiosis in allopolyploid species.Allotetraploid Brassica napus(AACC) is a model of natural hybridization of two diploid species Brassica rapa(AA) and Brassica oleracea(CC), which are originally derived from a common ancestor, but genomic structure probably diverged among these species through time after their establishment, giving rise to significant morphological and/or physiological changes. Therefore, the objective of this study is to investigate the relationships between A and C chromosomes during meiosis of allotriploid Brassica hybrids(ACC) at molecular and cytological levels, which result from the interspeci?c cross between natural B. napus and B. oleracea., The chromosome of abnormal behavior in allotriploid Brassica hybrids analysed through the observation about meiosis, which compared with parent plants. The relationship between the A chromosomes and C chromosomes used the study of GISH in allotriploid Brassica hybrids. The changes of gene expression were assessed by the method of quantitative real-time PCR.1 、 Through interspecific hybridization successfully obtained the allotriploid Brassica hybrids, which was no obvious different in vegetative development of somatic tissues in comparison to the parent plants. But the fertility rate and pollen grains of viability reduced significantly. The leaf morphologies and flower size of allotriploid Brassica hybrids were intermediate to the parent plants. As with parent plants fructification, the allotriploid Brassica hybrids is sterile with the shortened and underdeveloped siliques.2 、 The cytological observation showed that the meiosis was significantly irregular in allotriploid Brassica hybrids compared with parent plants, the multivalent and univalent were frequently observed at diakinese, and chromosomes aligned chaotically at metaphase I, this abnormalities lead to subsequent improperchromosome segregation, which chromosome bridges and lagged chromosomes occured from later metaphase I to anaphase II during meiosis. The GISH analyses showd the synapsis is not only autosynedsis between C chromosomes, but also allosyndesis between A chromosomes and C chromosomes, lead to unsynchronized segregation and the number of A chromosomes in nuclei of allotriploid Brassica hybrids were different. This is a reason for the pollen grains of viability reduced.3、Simultaneously, we also noticed that meiosis related genes were abruptly down regulated in allotriploid Brassica hybrids, which analysed by quantitative real-time PCR. The data clearly reflect the distinct expression of the six meiosis genes under investigation between allotriploid Brassica hybrids and Brassica oleracea, especially ASY1 、 DMC1 and SPO11-1 showed relatively reduced expression, which likely accounted for irregular scenario of meiosis course in these synthetic hybrids.