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Somatic Chromosomal Irregularities in Nicotiana plumbaginifolia Viv.¹

Nicotiana tabacum L. x N. plumbaginifolia Viv. hybrids are characterized by somatic chromosomal irregularities involving chromosomes contributed by N. plumbaginifolia. Chromosomal irregularities were observed in smear preparations of root tips and corollas of N. plumbaginifolia; none were observed in similar tissue from N. tabacum. Irregularities in seedling root tips included; micronuclei, extra and missing chromosomes at metaphase, fragments, anaphase bridges, laggards, and extra long metaphase chromosomes suggestive of dicentrics. Two and four year old seeds produced a much higher frequency of these irregularities than seed that was 2-3 months of age. Only corolla tissue from fresh seed was examined and aberrations were seldom observed. Chromsomal irregularities, detected in tissue of N. plumbaginifolia, may be associated with a seedling stress period marked by retarded growth and chromosome irregularities in a tabacum-plumbaginifolia hybrid. In N. plumbaginifolia, the aberrations appear to be associated with aged seed whereas aberrancy in the tabacumplumbaginifolia hybrid may be partly a function of interspecific hybridity.

² Assistant Professor of Agronomy, University of Kentucky, Lexington, Kentucky, 40506.

Received for publication July 20, 1967.