RICHARDSON, ADJOA O.*, QUI-YUN (JENNY) XIANG, AND CHUANZHU FAN. Department of Biological Sciences, Idaho State University, Pocatello, ID 83209. - Microsatellite analysis of the hybrid zone in the Buckeye Genus Aesculus L. (Hippocastanaceae).
Introgressive hybridization plays an important evolutionary role in
plants. However, studies of the genetic structures of natural hybrid
zones are often hindered by the lack of sensitive molecular markers.
We employed the highly sensitive genetic markers from microsatellte
loci to 1) define the genetic structure of a broad hybrid zone in
Aesculus L. involving A. pavia and A. sylvatica
and 2) to test previous hypotheses derived from allozyme and ISSR
data. Using PCR, eight pairs of microsatellite primers developed
specifically for Aesculus were used to amplify eight microsatellite
loci of populations representing pure parental species and hybrids.
The genotype of each locus was determined for each individual using an
ABI-377 automated DNA sequencer with GeneScan version 3.1 and the data
obtained analyzed with Genotyper version 2.0. Our preliminary results
indicated that these microsatellite loci are highly polymorphic.
Multiple alleles that differ in one to more than 15 nucleotides were
found for these loci. The loci contain unambiguous species-specific
alleles that can be used as species-specific markers. These
species-specific markers from the parental species were combined in
the hybrid populations. The results from the microsatellite analysis
are congruent with previous data from morphology, allozyme, and ISSR
in suggesting the existence of introgressive hybridization in the
hybrid zone, and most hybrids in the zone represent latter hybrid
Key words: genetic structure, Hybrid zone, microsatellite loci