Department of Botany, Madras University, P. G. Centre, Tiruchirapalli-620 020, India
Morphological and cytological characters of Solanum americanum Mill. (n= 12) and tetraploid S. nigrum L. (n=24) have been studied. The species were crossed and hybrids (3×) with 2n=36 chromosomes were produced. The lack of close genetic relationship between the two species is shown by the pairing behaviour of chromosomes of the hybrids. The pollen fertility of the hybrids was as low as 0∙35 and they did not set fruit. Chromosome doubling was induced in the hybrids with colchicine treatment. The amphidiploids were highly fertile (67∙09) with mostly normal pairing of chromosomes. These studies indicate that the hybrid sterility was mostly due to the chromosomal rather than genie causes.
