Cytogenetical studies in Phaseolus. II. Phaseolus mungo and tetraploid Phaseolus species and the amphidiploid

Cytological studies of triploid F₁ and amphidiploid of Phaseolus mungo L. (2n=22) × 4x Phaseolus sp. (2n=44) and comparative morphological studies of F₁ and parents are reported. At pachytene, the nucleolar chromosome of 4x Phaseolus sp., was not associated with nucleolus in the F₁ but was occasionally associated with accessory or principal nucleolus in the amphidiploid. In view of the already known potential autosyndesis in the chromosomes of 4x Phaseolus sp. a precise estimation of the chromosomal homology between the two species was not possible. However, a comparison of data on intragenomic homology in 4x Phaseolus sp., and chromosome pairing studies in the F₁, reveal the presence of chromosomal homology between the species. It is also evident that mungo genome is not totally homologous with either of the genomes of 4x Phaseolus sp. The predominantly bivalent synapsis of the amphidiploid lends support to this view.