Chromosome Complement Dosage in Relation to Seed Development of Species Hybrids in Nicotiana

Publisher Website
Google Scholar
Abstract
1. The failure to hybridize the species Nicotiana rustica and N. tabacum results from abortion of the hybrid embryos. Occasionally a hybrid seed germinates and develops into a vigorous but sterile hybrid. 2. By colchicine treatment of a diploid N. rustica x N. tabacum hybrid plant an amphidiploid was produced. When it was selfed, only about one seed per capsule germinated. On the other hand, the backcrosses amphidiploid x N. tabacum, amphidiploid x N. rustica, and N. rustica x amphidiploid have given a relatively high proportion of germinating seeds. These results, supplemented by additional crosses at various polyploid levels, have shown that changes of interspecific complement ratios of the hybrid embryos can modify incompatibility reactions and partially restore normal development of hybrid embryos. 3. An hypothesis was advanced that a 1:1 N. rustica to N. tabacum complement ratio in the embryos is the most incompatible combination, while deviations in either direction improve seed development. 4. The selfed progeny of the N. rustica-N. tabacum amphidiploid had reduced vigor or were even dwarf. Nevertheless, a higher proportion of their seeds germinated than of the seeds of the original amphidiploid plant. This improvement is explained on the basis of changes in the incompatibility reactions resulting from meiotic chromosomal aberrations. 5. Similar relationships were found to obtain in hybrids involving N. rustica and N. glutinosa and also in triple hybrids incorporating chromosome complements of N. rustica, N. tabacum, and N. glutinosa. 6. Limited observations indicated that species related to N. tabacum could substitute for the N. tabacum complement in increasing functional embryo production. The significance of results derived from a single hybrid combination involving N. suaveolens is obscure and awaits more detailed studies.

This publication has 0 references indexed in Scilit: