Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: ASSESSMENT OF NUCLEAR RFLPs AS A TAXONOMIC TOOL IN ALLIUM
SECTION CEPA (ALLIACEAE)
ASSESSMENT OF NUCLEAR RFLPs AS A TAXONOMIC TOOL IN ALLIUM
SECTION CEPA (ALLIACEAE).
James M. Bradeen, Ockyung Bark, and Michael J. Havey, USDA-ARS,
Department of Horticulture, University of Wisconsin, Madison, WI
53706.
Alliwn cepa (bulb onion), A. fistulosum (Japanese bunching
onion) and six wild species have been classified as members of
two distinct sections, Cepa and Phyllodolon, and as members of a
composite section Cepa. Maternal phylogenies estimated by
restriction enzyme analysis of the chloroplast DNA confidently
delineated a clade containing A. cepa, A. fistuloswn, A.
altaicwn, A. galanthum and A. vavilovii. We assessed the ability
of nuclear RFLPs to more thoroughly clarify relationships among
and within these species. While the maternal phylogeny did not
resolve affinities among these five species, nuclear RFLPs
identified three distinct informal groups, the Cepa, Altaicum,
and Galanthum Groups. Several distance analyses were used and
all identified the same three major informal groups. Nuclear
RFLPs provided no evidence for the division of these accessions
into two sections. Within the Cepa Group, both long day and
short day A. cepa culfivars from around the world were surveyed.
Comparatively few nuclear RFLPs were identified. Nuclear RFLPs
reflected known germplasm origins and suggested the long day
storage onion possesses a narrower genetic background than the
short day onion. One possible interpretation is that the short
day onion represents a progenitor state, with the long day onion
having been selected for production at higher latitudes. Given
the considerable nuclear variation observed among related species
in section Cepa, nuclear RFLPs are appropriate to resolve
taxonomic issues within a single species or among closely related
species in Allium section Cepa.
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