| Summary: | Hybrid lethality, a postzygotic mechanism of reproductive isolation, is a phenomenon that causes the death of F<sub>1</sub> hybrid seedlings. Hybrid lethality is generally caused by the epistatic interaction of two or more loci. In the genus <i>Nicotiana</i>, <i>N. debneyi</i> has the dominant allele <i>Hla1-1</i> at the <i>HLA1</i> locus that causes hybrid lethality in F<sub>1</sub> hybrid seedlings by interaction with <i>N. tabacum</i> allele(s). Here, we mapped the <i>HLA1</i> locus using the F<sub>2</sub> population segregating for the <i>Hla1-1</i> allele derived from the interspecific cross between <i>N. debneyi</i> and <i>N. fragrans</i>. To map <i>HLA1</i>, several DNA markers including random amplified polymorphic DNA, amplified fragment length polymorphism, and simple sequence repeat markers, were used. Additionally, DNA markers were developed based on disease resistance gene homologs identified from the genome sequence of <i>N. benthamiana</i>. Linkage analysis revealed that <i>HLA1</i> was located between two cleaved amplified polymorphic sequence markers Nb14-CAPS and NbRGH1-CAPS at a distance of 10.8 and 10.9 cM, respectively. The distance between these markers was equivalent to a 682 kb interval in the genome sequence of <i>N. benthamiana</i>.
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