Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 8pg1
LINKAGE OF TWO ALLOZYME LOCI WITH HYBRID STERILITY IN PHACELIA
DUBIA.
Foster Levy, Department of Biological Sciences, East Tennessee
State University, Johnson City, TN. 37614
The three varieties of Phacelia dubia are partially
isolated from each other by a nuclear-based reproductive barrier
manifested as partial sterility of both pollen and ovules in F1
hybrids. Four intervarietal hybrids and their reciprocals were
constructed to be heterozygous at each of four allozyme loci
(MDH, PGI, GOT-1, GOT-2) so that the varietal origin of each
allozyme allele was known. To determine whether a particular
marker locus was correlated with fertility, each of four
independent Fl hybrids and the corresponding Fl hybrids from
reciprocal crosses were backcrossed as pollen parents to
unrelated testers from each of the two parental varieties. Within
each of the four classes of backcross progenies, pollen
fertilities ranged from hybrid levels to complete fertility.
Two of the four isozyme loci showed a strong association with
hybrid fertility. For each locus, a Wilcoxon two-sample test was
used to test for an association of the allozyme genotype with
fertility. Parental and hybrid genotypes were treated as two
discrete classes in the tests. Pollen fertilities of the progeny
from hybrid backcrosses were treated as a continuous variable and
the distribution of fertility rankings of plants with parental
and hybrid genotypes were compared. Two marker loci (MDH; PGI)
showed no significant association with fertility indicating
independent segregation of alleles at these loci from alleles at
loci controlling fertility. For each of the two GOT loci, there
was a highly significant association of genotype and fertility
(p< 0.001). Only two of the 147 plants with a parental genotype
at either GOT locus showed pollen fertilities in the range of
Fl hybrids and both of those plants were GOT-1/GOT-2
recombinants.
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