Cytomorphological and Molecular Characterization of F1 Hybrids between Brassica tournefortii and B. rapa

Interspecific F-1 hybrids were synthesized between Brassica tournefortii (2n=20, TT) and B. rapa var. yellow sarson (NRCYS-05-02) (2n=20, AA) by sexual mating. The F(1)s were obtained only when B. tournefortii was used as the female parent. Morphological, cytological and sequence tagged microsatellite sites (STMS) based molecular analyses were carried out to confirm the hybrid nature of F-1 plants. Morphologically, the F-1 plants were intermediate for most of the morphological attributes. Although, the F(1)s showed poor pollen fertility, a few seeds were obtained from open pollination in the surroundings of B. rapa. The F-1 plants showed predominance of univalents (53.66%), a typical feature of wide hybrids. The occurrence of chromosome association ranging from bivalents (0-4), trivalent (0-1) and quadrivalent (0-1) in the F(1)s indicated homeologous pairing between the T and A genomes. STMS analysis of the parents and the F(1)s revealed a high degree of similarity (75%) and rearrangements in the two genomes during or after their fusion. The study suggests that B. tournefortii has partial genome homeology with B. rapa which could be exploited in crop improvement programmes, particularly breeding for tolerance/resistance to white rust and mustard aphid.