Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: Genetic Dissection of Fusiform Rust Resistance in
Loblolly Pine
Genetic Dissection of Fusiform Rust Resistance in
Loblolly Pine
H.V. Amerson 1, P.L. Wilcox 1,3, E.G. Kuhlman 2, D. O'Malley 1,
and R.R. Sederoff 1. Department of Forestry 1, North Carolina
State University, Raleigh NC, U.S.D.A. Forest Service
Laboratories 2, Athens GA, New Zealand Forest Research Institute
Ltd. 3, New Zealand.
We are completing the first phase of experiments to examine
the genetic basis for resistance to the causal agent of fusiform
rust, Cronartium quercuum f.sp. fusiforme (Cqf, in loblolly pine
(Pinus taeda), and in longer term to tag resistance genes with
molecular markers. To examine our hypothesis that resistance to
Cqf is under oligogenic control, a combinatorial experimental
design is being used. A putative heterozygous (Rr) mother tree
(10-5) along with four open pollinated daughters (B,C,D,E) were
all crossed to a highly susceptible pollen parent (rr). Progeny
from the resulting full-sib families were challenged with
inoculum from known single aeciospore lines and scored for
several greenhouse resistance symptom types. Since we chose a
susceptible pollen parent, we are initially examining only the
maternal contribution to the progeny genotype by constructing
RAPD maps using megagametophyte tissue. We have genotyped two
families to date: the mother tree, 10-5, and one daughter, B.
Forty-eight progeny have been genotyped for each and maps using
418 markers in 10-5 and 350 markers in B have been prepared.
Additional progeny in the two families are being screened using
framework RAPD markers. Putative associations between markers
and resistance (a >= 0.01) have been found in both families 10-5
and B. These associations are being further investigated by
bulking on markers of interest. Examination of other inoculum
treatments in these two families and the possible association of
these markers with resistance in the remaining families is still
to be tested.
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