LARA-CABRERA, SABINA I.* AND DAVID M. SPOONER. USDA, Agricultural Research Service; Department of Horticulture, University of Wisconsin, Madison, WI 53706. - Morphological and microsatellite variation of Mexican diploid wild potato species.
Solanum L. section Petota Dumort., the potato and its
wild relatives, contains over 200 wild species distributed from the
southwestern United States to south-central Chile. Most of these
species grow in the Andes, but the United States, Mexico, and Central
America contain about 30 taxa of diploids, tetraploids, and
hexaploids. Chloroplast DNA restriction site data show 13 of these 30
taxa to form a clade containing only diploid species, but there is low
resolution within this clade. In addition, some of these 13 taxa are
similar morphologically and may not be valid species. In preparation
for a monograph of sect. Petota from this region, we are
analyzing members of this clade with phenetic analysis of
morphological data, and two nuclear markers with the potential to show
better resolution than chloroplast DNA restriction site data.
Morphological data show extensive overlap of putative
"species-specific" characters, but most species can be
supported by multivariate techniques (except S. cardiophyllum
subsp. ehrenbergii, S. nayaritense, and S.
stenophyllidium that remain problematical). We here also report on
one nuclear marker, mapped microsatellites developed in Solanum
tuberosum, chosen because of their hypervariable nature.
Preliminary data, using ten microsatellite markers distributed over
seven chromosomes, strongly cluster some species (e.g., S.
jamesii) but other morphologically different species cluster
together, despite analyses of data as alleles or as each
microsatellite variant as unrelated characters. There is considerable
controversy regarding mutation processes of microsatellites and the
best analytical method for phylogenetic studies. Interestingly,
scoring each microsatellite variant as unrelated characters did a
"better" job of clustering taxa. Our results suggest that
microsatellites have reduced utility to analyze the United States,
Mexican, and Central American diploid species.
Key words: microsatellite, potato, Solanum sect. Petota, SSR