Cytogenetics of Nicotiana longiflora×Nicotiana glauca Back-Crosses Involving the Standard and Mutant Species of N. glauca

Abstract

Parallel lines of first and selfed back-cross populations of longiflora-glauca-longiflora hybrids involving both the standard and variant species of N. glauca (N. glauca W. 8400) were raised and studied. The variant W. 8400 maintained its heterozygosity even in the selfed back-cross progenies. Variations in plant habit, leaf characters and flower types were observed in high frequency as a consequence of chromosomal segregation.
The chromosome number ranged in the progenies from 20 to 40. By the complete pairing of the two races of glauca it is evident that they are identical cytologically. Pairing was complete in the back-cross between the 20 longiflora chromosomes with additional varying number of glauca univalents. The presence of glauca univalents suppressed the longiflora characters whereas the presence of longiflora univalents in addition to the diploid level of glauca complements, did not alter the basic glauca characters.
The possibilities and utility of building up of races with addition of alien chromosomes in the longiflora-glauca combination are discussed.