Production of Synthetic Brassica napus through Interspecific Hybridization between Brassica rapa and Brassica oleracea and Their Cross-Ability Evaluation

Synthetic B. napus was produced through interspecific hybridization between nine varieties of B. rapa and only one exotic variety of B. oleracea var. alboglabra along with exogenous application of gibberellic acid (GA3) before pollination. A total of eighteen crosses including their reciprocals were made between the two species. Crossability in both way directions between the two species of Brassica was not equally success. The degree of success was significantly influenced by maternal genotypes. On average, the cross success was 8.42% when the varieties of B. rapa used as female parents in contrast to 2.88% when B. rapa used a pollen parents. Among the four concentrations (25, 50, 75 and 100 ppm) of GA3, 75 ppm gave highest response for different crossability characters in both way cross directions. The hybrids contained 19 somatic chromosomes which were the sum of the gametic chromosome number of B. rapa and B. oleracea. Of the two methods, followed to induce chromosome doubling in the adult plants, the Modified Injection Method was found more effective than the Cotton Plug Method. Among different concentration of colchinine 0.20% gave the highest success (66.67%) of chromosome doubling in the hybrids. All the colchiploid (C1) plants contained 38 chromosomes in their somatic cells which were the sum of the somatic chromosomes of both species. The genomes of resynthesized lines were also identified through Brassica genome specific SSR markers. The presence of markers for both A and C genome was detected in resynthesized lines suggesting that their genomic constitution was AACC.