Abstract:

It was found that there were strong correlations between genetic distance and mid parent heterosis for seed yield in rapeseed. So the increasement of genetic diversity of B. napus is an important way to increase the yield of oilseed rape. There are two strategies to enhance the diversity of B. napus. One is to resynthesize B. napus artificially by sexual or somatic hybridization between B. rapa and B. oleracea, another is to introduce good characters of other Cruciferae materials into B. napus. However, multivalent or univalent formation at meiosis result in low fertility and low seed setting in these resynthesized lines, which were less direct utilized in seed production. In order to overcome this shortcoming, a new breeding strategy was conducted in our experiment, using the plants with 38 chromosomes (A^rA^rC^cC^c) selected from the progenies of pentaploid hybrids (A^rAⁿB^cCⁿC^c) derived from the hybridization between hexaploid (A^rA^rB^cB^cC^cC^c) and natural B. napus (AⁿAⁿCnCn). Intersubgenomic hybrids of rapeseed were produced by hybridization between the novel genotype B. napus (A^rA^rC^cC^c) and natural B. napus, Xiangyou 15 (AⁿAⁿCⁿCⁿ). The cytological studies on the intersubgenomic hybrids (A^rAⁿC^cCⁿ) revealed that the main chromosome configuration of pollen mate cell (PMCs) was 19 bivalents, the trivalents and quarivalents were also appeared in some cases at metaphase Ⅰ. The assessments of homologous chromosomes and chromosome monads at anaphase Ⅰ and anaphase Ⅱ were normal except for some laggards that were observed in a few cases. It indicated that the chromosome pair of A^r/Aⁿ and C^c/Cⁿ in the intersubgenomic hybrids could be normally paired in most cases. The genetic differentiation of subgenomes between A^r and Aⁿ may influence the meiosis of intersubgenomic hybrids.

Key words: New-typed Brassica napus, Cytological analysis, Intersubgenomic hybrid