Studies On Distant Hybridization Between Raphanus Sativus And Brassica Napus

Brassica napus is an amphidiploid species originated from interspecific hybridization between B.rapa and B.oleracea. Due to the short history of origin and cultivation, the narrow genetic backgrounds are highlighted in B.napus. Natural B.napus strictly abides by the principle of pairing of homologous chromosomes and presents rare abnormal chromosome behavior during meiosis, while resynthesized B.napus is unstable with abundant genetic variation. Though hybridization between natural and synthesized B.napus and R.sativus, it could transfer related traits and widen the genetic basis each other, and may create new biological types.At present, though a few researches on distant hybridization and cytogenetical studies of the hybrid between natural B.napus and R.sativus are reported at home and abroad. At the same time, there are still no reports on distant hybridization and cytogenetical studies of the hybrid between resynthesized B. napus and R.sativus.Aimed to broaden the genetic basis of B.napus and provide the theory basis for creation of new biological materials. In this study, some hybrids between natural and synthetic B.napus and R.sativus were obtained by ovule culture. The hybrids were characterized in morphology, molecular markers and cytology. The main results are as follows:1. Hybridizations of natural and synthesized B.napus and R.sativus had a certain pre-fertilization compatibility and the main incompatibility were post-fertilization embryo development barriers. The parental genotypes affected the hybridization compatibility. The pre-fertilization affinity of synthesized B.napus and R.sativus was lower than that between natural B.napus and R.sativus.2. The medium of MS+IAA2.0mg/L+6-BA0.5mg/L+sucrose3%+agar7g/L was suitable for hybrid ovules culture of resynthesized B.napus and R.sativus, but was less suitable for the hybrid of natural B.napus and R.sativus. In total, we got18hybrids of B. napus and R.sativus, including1hybrid of natural B.napus and R.sativus,17hybrids of resynthesized B.napus and R.sativus by ovule culture. Among the hybrids,3hybrids were naturally doubled, and the authenticity was identified by SSR markers, the observation of somatic chromosome number and the genomic in situ hybridization of meiotic chromosomes in pollen mother cells.3. The morphology of the hybrids was intermediated between their parents B.napus and R.sativus, which not only had some of morphological characteristics of female parent, but also had those of male parent. The hybrids also had some new features. Overall, there were2kinds of flower color in the hybrids. One kind was white which was different from the purple red of the male parent and the yellow or creamy yellow of the female parent, while another kind of flower had white petals with purple stripes, which was inclined to R.sativus.4. All haploid hybrids had no fertile pollens and could not set seeds by artificial pollination. The doubled hybrids had a small amount of fertile pollens. The seed-set rates of the3double hybrids K1190D, K1039and K393D were0,2.60%and1.27%respectively. Under open pollination condition, haploid and doubled hybrids could bear a small amount of seeds.5. The average chromosome pairing configurations of the double hybrid K1190D, haploid hybrid K1190, doubled hybrid K393D and haploid hybrid K393were0.971+19.95II+2.29III+1.72IV+0.14V+0.07VI,2.47I+9.96II+2.07III+1.95IV+0.27V+0.16VI,2.12I+17.90II+1.64III+2.26IV+0.36V+0.37VI and4.38I+6.59II+1.13III+1.15IV+0.27V+0.17VI, respectively. No matter of a hybrid of natural B.napus and R.sativus or a hybrid of resynthesized B.napus and R.sativus hybrid, both of haploid and doubled hybrids formed univalent and multivalent except bivalent, which proved that the hybrids were not stable and would produce a wide range of variation. The bivalent number of natural B.napus and R.sativus hybrid was a higher than that of resynthesized B.napus and R.sativus hybrid, which suggested that resynthesized B.napus and R.sativus hybrid had greater instability and variability.6. During meiosis of the pollen mother cells of doubled hybrid K1190D and K393D, haploid hybrid K1190and K393, high proportion of PMCs with chromosome bridge(s) and lagging chromosome(s) at anaphase I, chromosome irregular segregation and multi-microspores were observed. It also explained that the hybrid between B.napus and R.sativus was unstable and might produce a wide extension of variation.