Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: MAPPING THE STRAWBERRY GENOME
MAPPING THE STRAWBERRY GENOME
Thomas M. Davis and Hongrun Yu. Department of Plant Biology,,
University of New Hampshire, Durham, NH 03824.
Genetic analysis of the commercially cultivated strawberry,
Fragaria x ananassa, has been hampered by its octoploid
(2n=8x=56) genomic structure. To circumvent this difficulty, we
are using closely related diploid species (primarily F. vesca and
F. viridis) as a "model system" for strawberry genome mapping.
With the aim of defining the seven basic strawberry linkage
groups, we have collected segregation data on RAPD'S, isozymes,
and morphological markers from segregating progenies resulting
from crosses between an interspecific (vesca x viridis) hybrid
and two F.vesca 'Alpine' cultivars, 'Baron Solemacher' and
'Yellow Wonder'. All but one of 80 segregating markers have been
assigned to four linkage groups. This deficiency (seven groups
were expected) suggests the existence of translocation
heterozygosity in the interspecific hybrid parent, an unexpected
result based on published cytological evidence that F. vesca and
F. viridis share a common (AA) genomic constitution. Despite
this complication, we have used advanced generations to identify
and confirm RAPD and isozyme tags for genes of economic interest,
including fruit color and runner formation, and have detected
apparent single gene segregation for resistance to red stele root
rot, an important fungal disease. The feasibility of detecting
codominant RAPD markers, and of comparing RAPD markers and
RAPD-based linkage groups among Fragaria species at different
ploidy levels is being investigated by marker cloning and
Southern analysis. RAPD bands that are polymorphic among diploid
accessions are seldom detectable at higher (6x,8x) ploidy levels,
but some monomorphic bands are detectable across-all ploidy
levels. Results indicate that RAPD markers can useful for
phylogenetic analysis at the diploid level, but less so across
ploidy levels, in Fragaria.
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