Abstract
BackgroundA linkage map consisting of 24 linkage groups has been constructed using simple sequence repeat (SSR) markers in Nicotiana tabacum. However, chromosomal assignments of all linkage groups have not yet been made. The Q chromosome in N. tabacum encodes a gene or genes triggering hybrid lethality, a phenomenon that causes death of hybrids derived from some crosses.Methodology/Principal FindingsWe identified a linkage group corresponding to the Q chromosome using an interspecific cross between an N. tabacum monosomic line lacking the Q chromosome and N. africana. N. ingulba yielded inviable hybrids after crossing with N. tabacum. SSR markers on the identified linkage group were used to analyze hybrid lethality in this cross. The results implied that one or more genes on the Q chromosome are responsible for hybrid lethality in this cross. Furthermore, the gene(s) responsible for hybrid lethality in the cross N. tabacum × N. africana appear to be on the region of the Q chromosome to which SSR markers PT30342 and PT30365 map.Conclusions/SignificanceLinkage group 11 corresponded to the Q chromosome. We propose a new method to correlate linkage groups with chromosomes in N. tabacum.
Highlights
Hybrid lethality is a phenomenon that causes death of hybrids, and is one of the postzygotic mechanisms of reproductive isolation
Our previous studies revealed that many species of section Suaveolentes yield inviable hybrids after crosses with N. tabacum [14,15,16]
N. ingulba, which belongs to section Suaveolentes, is one species yielding inviable hybrids
Summary
Hybrid lethality is a phenomenon that causes death of hybrids, and is one of the postzygotic mechanisms of reproductive isolation. Hybrid lethality is considered to play a crucial role in the evolution of plants An example supporting this hypothesis is that hybrid seedlings between two sympatric species, Papaver dubium and P. rhoeas, die, indicating that hybrid lethality functions as a barrier to gene flow between these species [6]. The hybrid lethality phenotype is specific to particular cross combinations in Nicotiana Hybrid lethality in this genus is classified into five types based on the observed phenotype: Type I, browning of shoot apex and root tips; Type II, browning of hypocotyl and roots; Type III, yellowing of true leaves; Type IV, formation of multiple shoots; and Type V, fading of shoot color [1,9]. The Q chromosome in N. tabacum encodes a gene or genes triggering hybrid lethality, a phenomenon that causes death of hybrids derived from some crosses
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