Studies On Fertility And Crossability Of Amphidiploids Between Raphanus Sativus And Brassica Alboglabra

R. sativus-B. oleracea amphidiploid (2n = 36, RRCC) called Luobojielan have good prospects for the breeding of fodder crops or being used as a genetic bridge for intergeneric gene tranfer, but the lower seed fertility limited its practical utilization. In the present study, Luobojielan amphidiploids were obtained from R. sativus × B. alboglabra Bailey crosses, and repeated selection with special attention to seed fertility was made from F4 to F10. The techniques of conventional cytology, genomic in situ hybridization (GISH) and amplified fragment length polymorphism (AFLP) were used to monitor the genetic changes accompanying the improvement of seed fertility. The crossability of Luobojielan with R. sativus and several Brassica species were investigated by sexual hybridization. The main results were as follow:1. The pollen stainability was 51% and 58% in F4 and F5, respectively, and reached about 80% after F6. The number of siliques per plant was no more than 210 in F4 and F5 and sharply increased to 534 in Fβ, and then gradually increased and reached 726 in F10. Seeds per silique was 3.7 in F4 with 3.5 shriveled ones and reached 14.9 in F10 with only 2.8 shriveled ones. The seed yield per plant was 0.6 g in F4 and reached 32.3 g in F10. Apparently the obstacles of silique and ovule development were the main limited factors of seed yield in the lower generations of Luobojielan.2. Luobojielan was actually mixoploid with 20 to 38 chromosomes in somatic cells of F4 and F5 plants and 32 to 38 chromosomes after F6. The euploid cells (2n = 36) were predominant in six F4 plants, 40.7% F5 plants, 51.9% F6 plants and every plants after F7. The frequency of euploid cell in every plant increased from 44.4%～66.7% in F4 to about 80% after F7. Plants with highest frequency of euploid cell showed higher seed set in lower or higher generations.3. The abnormal meiotic behaviors were generally observed in the 6 F4 plants, such as multivalents including Ⅳ, Ⅵ and Ⅹ at diakinesis, asynchrony in metaphase Ⅰ / Ⅱ, anaphase Ⅰ / Ⅱ, chromosome bridge and disjunction in anaphase Ⅰ /Ⅱ, asymmetrical separation and division in telophase Ⅰ / Ⅱ. In the following generations, the number of multivalents decreased, the pairing patterns of multivalents were changed from 'twist' to 'circle', chromosome bridge and laggards became rare. In F10, more than 94% cells had 18 Ⅱ at diakinesis, the chromosomal behaviors in anaphase Ⅰ and Ⅱ were also regular, which showed the differentiation of homeologous chromosomes must have been occurred.4. AFLP analysis revealed that about 34% B. alboglabra specific bands and 30% R.