Genetic structure of the four wild tomato species in the Solanum peruvianum s.l. species complex

The most diverse wild tomato species Solanum peruvianum sensu lato (s.l.) has been reclassified into four separate species: Solanum peruvianum sensu stricto (s.s.), Solanum corneliomuelleri, Solanum huaylasense, and Solanum arcanum. However, reproductive barriers among the species are incomplete and this can lead to discrepancies regarding genetic identity of germplasm. We used genotyping by sequencing (GBS) of S. peruvianum s.l., Solanum neorickii, and Solanum chmielewskii to develop tens of thousands of mapped single nucleotide polymorphisms (SNPs) to analyze genetic relationships within and among species. The data set was condensed to 14,043 SNPs with no missing data across 46 sampled plants. Origins of accessions were mapped using geographical information systems (GIS). Isolation by distance, pairwise genetic distances, and number of clusters were estimated using population genetics approaches. Isolation by distance was strongly supported, especially between interspecific pairs. Eriopersicon (S. peruvianum s.s., S. corneliomuelleri, S. huaylasense) and Arcanum (S. arcanum, S. neorickii, S. chmielewskii) species groups were genetically distinct, except for S. huaylasense which showed 50% membership proportions in each group. Solanum peruvianum and S. corneliomuelleri were not significantly differentiated from each other. Many thousands of SNP markers were identified that could potentially be used to distinguish pairs of species, including S. peruvianum versus S. corneliomuelleri, if they are verified on larger numbers of samples. Diagnostic markers will be valuable for delimiting morphologically similar and interfertile species in germplasm management. Approximately 12% of the SNPs rejected a genome-wide test of selective neutrality based on differentiation among species of S. peruvianum s.l. These are candidates for more comprehensive studies of microevolutionary processes within this species complex.