EN
Near-amphihaploid hybrid plants of Nicotiana tabacwn x N. alata disomic for some N. alata chromosomes were nearly completely self- and cross-sterile but under open pollination conditions occasionally set poorly filled seed capsules containing very small numbers of seeds. Six plants from those seeds which survived to maturity resembled N. alata. Upon cytological examinations five plants were found to have the diploid chromosome complement of N. alata (2n=18), which suggested their androgenetic origin following outcrossing with paternal N. alata. The sixth plant had 9 bivalents and 11 univalents, which was indicative of its hybrid origin. Unlike the self-incompatible N. alata parent, N. alata-like hybrid derivatives were self-compatible. Surprisingly, the selfed progeny of the 18-chromosome plants showed sensitivity to tentoxin, a chloroplast trait characteristic of paternal N. alata but hardly compatible with its cytoplasmic lineage since the tentoxin-insensitive N. tabacum was the cytoplasmic parent of the hybrid. The progeny of the 29-chromosome plant was tentoxin-insensitive, which agreed with the parentage of the hybrid. Populations derived from the 18-chromosome plants were highly uniform but differed sharply from one another. The offspring of the 29-plant was highly heterogeneous mainly because of univalent segregation in that progeny.