PRODUCTION AND CHARACTERIZATION OF INTERGENERIC SOMATIC HYBRIDS OF TRACHYSTOMA-BALLII AND BRASSICA-JUNCEA

Intergeneric somatic hybrids, Trachystoma ballii (2n = 16) + B. juncea (2n = 36), were obtained by fusing mesophyll protoplasts of T. ballii and hypocotyl protoplasts of B. juncea using polyethylene glycol. The heterokaryotic fusion frequency was around 23%. Plants were regenerat ed from 10 out of 2 x 10(4) calli of which four were hybrids. Hybrids were intermediate between the parents in general morphology. However, in some characters one of the parents dominated. All the plants were s ymmetric in their chromosomal constitution as revealed by the formatio n of 26 bivalents at metaphase-I of meiosis. Two trivalents and 2 univ alents were also observed in some pollen mother cells. Hybrid nature w as also confirmed by 'Southern' hybridization of DNA of one regenerate d plant restricted with Hind III and probed with the nick translated p lasmid pTA71 carrying a wheat nuclear r-DNA sequence. Hybrid plant RT 1 showed bands characteristic of both parents. All the plants were abs olutely pollen sterile. However, on backcrosses to B. juncea seeds wer e obtained.