ARS | Publication request: Unraveling the Evolutionary History of Wild Potatoes and Tomatoes

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2009
Publication Date: July 15, 2009
Citation: Rodriguez, F., Spooner, D.M. 2009. Unraveling the Evolutionary History of Wild Potatoes and Tomatoes [abstract]. Botany & Mycology 2009. p. 26.

Technical Abstract: Phylogenies reconstructed with only one or a few independently inherited loci may be unresolved or incongruent due to taxon and gene sampling, horizontal gene transfer, or differential selection and lineage sorting at individual loci. In an effort to remedy this situation, we examined 24 conserved orthologous set (COS) nuclear loci to elucidate the phylogenetic relationships among 29 diploid Solanum species in the sister clades tomato and potato. Among potatoes, when total evidence is invoked, one single predominant history is highlighted with complete resolution within and among the three main clades. This history supports the hypothesis of a North and Central American B-genome origin of Solanum sect. Petota, and shows a clear division between A and B genomes. On the other hand, when a prior agreement approach is invoked alternative potato evolutionary histories were also revealed but with less support, that were revealed in previous phylogenetic studies with single genes. In the case of tomato, the analyses with all sequence data completely resolved 19 of 21 clades and for the first time revealed the monophyly of five clades and gave further support for the recent segregation of new species from the former Solanum peruvianum. This study confirms and quantifies the utility of using DNA sequences from different parts of the genome in phylogenetic studies to avoid possible bias in the sampling and shows that 11-18 loci are enough to get the dominant history, but more loci would be needed to discern the distribution of gene genealogies in more depth, and thus detect which mechanism most likely shaped the discordance. We are screening more COS, using the single strand conformational polymorphism (SSCP) technique to separate all the alleles without the necessity of cloning and using an asymmetric PCR to reduce the number of bands to be sequenced.