2017 ASHS Annual Conference

Hybrid lethality is sometimes observed in interspecific F₁ hybrids, thus limiting opportunities for creation of new hybrids of interest for ornamental purposes, or as starting points for introgression of diverse germplasm into cultivated row crop species. An example of a post-zygotic interspecific hybridization barrier in Nicotiana is the seedling lethality that occurs in the majority of F₁ progeny produced by a cross between N. tabacum and its wild relative, N. africana. Indeed, this reaction provides an expedient system for the identification of maternal haploids of N. tabacum that result from parthenogenesis. To gain insight on genetic mechanisms affecting interspecific lethality in plants, we attempted to identify the N. tabacum genetic factor involved in the lethality reaction in the N. tabacum x N. africana cross. We utilized an approach combining transposon-tagging, phenotypic markers, and molecular markers to identify a N. tabacum candidate gene contributing to seedling lethality. The gene belongs to a class of coiled-coil nucleotide-binding site—leucine-rich repeat (CC-NLR) proteins, which are the largest class of plant defense proteins. Ongoing work to functionally validate the role of this gene in the interspecific lethality reaction is being carried out using a CRISPR/Cas9 knockout approach. The research findings provide a greater understanding of factors contributing to plant speciation and increased insight on genetic limitations to interspecific hybridization in plants.