Meiosis in the Hybrid Between Greengram and Rice Bean

Meiotic analysis of the interspecific hybrid between green gram (Phaseolus aureus Roxb., 2n= 22) and rice bean (P. calcaratus Roxb., 2n=22) belonging to the asiatic group of Phaseolus revealed: 0) presence of large number of univalents ranging from 6 to 22, (ii) disjunction of paired homologues at the end of diakinesis, (iii) presence of few trivalent associations, chromosome bridges and laggards indicating heterozygosity of the hybrid and (iv) irregularities in movement of univalents leading to the formation of dyads with multiple number of nuclei. These resulted in total failure of seed set in the hybrid. Hybrid sterility might be the major isolating mechanism between these two species under natural conditions.