[Identification and analysis of asymmetric somatic hybrids between B. oleracea and B. nigra]

Asymmetric interspecific somatic hybrids between Brassica oleracea var. botrytis and B. nigra were produced by PEG-induced fusion of protoplasts radiated by different doses of UV. B. nigra, genotype St.461, has resistance to black rot, black leg and clubroot diseases which are popular in cabbage production. The regenerated plants were analyzed by several means including morphology observation, relative DNA content measurement by flow cytometry (FCM), chromosome counting, DNA molecular marker. Morphology observation indicated that the regenerated plants varied in morphology from intermediate type to cauliflower type. DNA contents of 20% regenerated plants were less than the sum of donor and recipient. Number of chromosomes in 23% of the regenerated plants were less than the sum of both parents. DNA molecular marker analysis (SRAP) demonstrated that the genetic information from the recipient parent was retained more or less complete and intact in the hybrids, while specific amplification bands of donor genome were lost in the hybrids from 20% to 97.77% . Furthermore, black-rot resistance test was performed in twenty-two regenerated plants, and seventeen of which showed good resistance against Xamthomonas campestris pv campestris. That gave the elementary proof of transferring of alien pathogen resistant genes from wild B. nigra to B. oleracea via UV mediated asymmetrical somatic hybridization. In conclusion, UV irradiation induced production of asymmetric hybrids between cauliflower and black mustard. Chromosome elimination or a limited introduction of donor chromosomes occurred in most of the hybrids, however, the degree of elimination was independent on UV doses.