Cytomorphological Studies of Spontaneous and Artificial Triploids and Their Role in the Evolution of Hexaploid Solanum nigrum L

Abstract

Interspecific hybrids (n=18) were obtained in between S. villosum×S. americanum using higher chromosomal form as a pistillate parent and compared cytomorphologically with natural triploid hybrids. Hybrids exhibit vigorous growth with abundant flowering but failed to produce fruits in both cases. The resulting hybrids showed highly irregular meiosis with consistant presence of univalents and trivalents in the pollen mother cells. High pollen sterility indicated the dissimilarities of parental genomes due to chromosomal cause rather than genic. Triploids are originated from the union of an unreduced female gamete produced spontaneously with a normal male gamete. Results of floral parts indicates that triploid evolved from diploid populations and later by which hexaploid S. nigrum evolved.