ARS | Publication request: Phylogenetic relationships of Solanum series Conicibaccata and related species in Solanum section Petota inferred from five conserved ortholog sequences

Submitted to: Systematic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 22, 2010
Publication Date: February 22, 2011
Citation: Fajardo, D., Spooner, D.M. 2011. Phylogenetic relationships of Solanum series Conicibaccata and related species in Solanum section Petota inferred from five conserved ortholog sequences. Systematic Botany. 36(1):163-170.

Interpretive Summary: Wild potatoes comprise a group of about 100 wild species relatives of cultivated potatoes, and are of great use to plant breeders to improve the quality of cultivated potatoes. Wild potatoes are widely distributed from southern Mexico to central Chile. This study uses DNA characters to study a subgroup of wild potatoes, consisting of about 40 species, technically referred to as Solanum series Conicibaccata. Some species in series Conicibaccata (called diploids)have only one group of chromosomes, and other species have 2 or 3 sets of chromosomes (called as polyploids). This study shows two important things: 1) The polyploids are formed by the combining of genes from two unrelated groups of species, and 2) combined with data of plant form (morphology) from a prior study; there are far fewer than 40 species in series Conicibaccata. These results are of critical value for the next phase of this study, writing a taxonomic monograph of wild potatoes. This monograph, combining data from these results, and other data such as distribution and taxonomic data, will aid plant breeders and all other users of wild potatoes.

Technical Abstract: Solanum series Conicibaccata is the second largest series in sect. Petota, containing 40 species widely distributed from southern Mexico to central Bolivia. It contains diploids (2n = 2x = 24), tetraploids (2n = 4x = 48) and hexaploids (2n = 6x = 72), and a limited number of examined species have been shown to be allopolyploids. Previous morphological and molecular studies using plastid DNA failed to discriminate clear species boundaries and showed low resolution inside the series and among species. Conserved orthologous nuclear DNA sequences (COSII) were used to compare the relationships among 72 accessions from 22 species from series Conicibaccata and 42 additional related accessions from other series. The results supported previous results showing the diploid members of series Conicibaccata to be related to other South American “clade 4” species, and showed all of the polyploids to be allopolyploids with members of clade 4 and other South American species of “clade 3”. Low bootstrap support values and morphological similarity suggest very recent origins and show the need for a reduction in recognized species in series Conicibaccata.