Interrelationship in the Solanum Nigrum Complex

The morphological dissimilarity and high intersterility between S. vitlosmn and the French hexaploid S. nigrum indicate their distant relationship. In pentaploid hybrids of the two taxa, the occurrence of as many as 24 bivalents and the rest of the chromosomes as univalents suggest that S. villosum is closely related to tetraploid parent of the French hexaploid S. nigrum. In pcntaploids, the breakdown of meiosis and high sterility are attributed mostly to chromosome number and structural differences between chromosomes of the parents. In addition the existence of genie sterility too is exemplified by the study of F₂ and F₃ progeny of pentaploids. It has been concluded that the barrier to gene flow between the two taxa is due to differences in chromosome number and structure, and to genic factors.