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TITLE:
Determining Pollen Parent of Backcross Plants from Field Grown Wheat
x Jointed Goatgrass Hybrids
PERSONNEL: Robert Zemetra,
University of Idaho
Carol
Mallory-Smith, Oregon State University
Brad Hanson, Ph.D. GRA, University of Idaho
Maqsood Rehman, M.S. GRA, University of Idaho
TIMELINE: July 1, 2000 to June 30,
2003: Objectives 1 and 2 are on schedule; Objective 3 will be
completed 6 months later than originally planned.
ORIGINAL HYPOTHESIS: Wheat x
jointed goatgrass hybrids will produce seed under many different
environmental conditions and seed production is not related to
specific wheat cultivars. Molecular techniques can be used to
determine whether wheat or jointed goatgrass was the pollen parent.
A herbicide-resistance gene from wheat will move to jointed
goatgrass and produce herbicide-resistant hybrids.
SUMMARY OF PROGRESS: Significant
progress has been for made on all three objectives. The BC1
seeds harvested over two years from Idaho, Oregon and Washington
have been germinated and total chromosome number and number of C
genome chromosomes is being determined. Germination of the BC1
seed averaged 83% with a mean chromosome number of 42.8 with a range
of 33 – 56. The mean number of C genome chromosomes in the BC1
plants was 5.9 with a range from 4 – 11. Based on results to date,
only 8% of the BC1 plants were produced by a backcross to
jointed goatgrass. Jointed goatgrass from the 2000-2001 pollen flow
study was harvested and 5 hybrids were recovered after an initial
screening with imazamox. The 2001-2002 study was harvested and will
be screened this winter. A third field study was planted Fall 2002
to supply additional data.
OBJECTIVES:
1.
Harvest wheat x jointed goatgrass hybrids from fields in
Idaho, Oregon, and Washington to determine the frequency of seed set
on the hybrid plants.
2.
Use GISH analysis to determine if the pollen parent of the
BC1 seed was wheat
or jointed goatgrass.
3.
Test pollen flow in field plots of Clearfield wheat for
travel distance and pollen viability.
EXPERIMENTAL DESIGN:
Objective 1. Harvest wheat x jointed goatgrass hybrids from fields
in Idaho, Oregon, and Washington to determine the frequency of seed
set on the hybrid plants.
Collections of wheat x jointed
goatgrass hybrids were made in Idaho, Oregon, and Washington. Up to
25 hybrid plants were collected per site. Each hybrid spike was
checked for seed and data were recorded by plant and by site.
Objective 2. Use GISH analysis to determine if the pollen parent of
the BC1 plants was wheat
or jointed goatgrass.
The harvested BC1 seeds
will be tested to determine the pollen parent using GISH. Roots
will be collected and treated according to standard cytological
procedures. GISH technique as described by Wang et al.
(2000) will be used with Aegilops markgrafii DNA being used
as the C genome probe and bread wheat Triticum aestivum being
used as the blocking DNA for the A, B and D genomes. After
treatment, the preparations will be observed on a fluorescent
microscope to count the number of C chromosomes in each backcross.
Any plant with 7 or less C chromosomes will be considered pollinated
by wheat and any backcross with 8 or more C chromosomes will be
considered pollinated by jointed goatgrass. Overall frequency of
wheat as a pollen parent compared to jointed goatgrass as a pollen
parent will be compared to determine a more realistic estimate of
the potential for jointed goatgrass derived backcrosses and
subsequent gene movement from wheat to jointed goatgrass to occur in
the field.
Objective 3. Test pollen flow in field plots of Clearfield wheat
for travel distance and pollen viability.
A Nelder plot with Clearfield wheat
in its center plot as a pollen source and rays of jointed goatgrass
radiating outward will be used to determine pollen movement. Winter
barley will be used between the rays of jointed goatgrass. The
pollen of wheat, jointed goatgrass, and barley each has a
distinctive morphology. The jointed goatgrass will be harvested in
designated blocks. Distance of viable pollen flow and hybridization
will be measured.
PROGRESS:
Objective 1. Harvest wheat x jointed goatgrass hybrids from fields
in Idaho, Oregon, and Washington to determine the frequency of seed
set on the hybrid plants.
Hybrids were collected over two
years from sites in Idaho, Oregon, and Washington. BC1
seed was found on the hybrids collected in all three states. Amount
of seed set varied from 0.3 to 4.9% with some of the variability due
to location and the crop in the field. Overall percent germination
of the BC1 seed was 83%.
Objective 2. Use GISH analysis to determine if the pollen parent of
the BC1 plants was wheat
or jointed goatgrass.
Chromosome counts of the BC1
seed harvested over the two years averaged 42.1 chromosomes with a
range of 33 to 56. The 56 chromosome plants indicate that some
level of chromosome restitution was occurring in the hybrid plants
during meiosis resulting in all 35 chromosomes in the hybrid being
passed to the next generation. GISH analysis is currently being
done on these plants to determine the number of C genome chromosomes
in the BC1 generation. To date 65 plants have been
counted with an average of 5.9 C genome chromosomes per plant with a
range of 4 to 11 C genome chromosomes. Of these plants, only 5 had
more than 7 C genome chromosomes indicating that only 8% of the BC1
plants were produced from a backcross with jointed goatgrass as a
recurrent parent. This indicates that the chance of gene flow via
backcrossing is lower than expected based on the level of female
fertility observed in the wheat x jointed goatgrass hybrids.
Objective 3. Test pollen flow in field plots of Clearfield wheat
for travel distance and pollen viability.
Seed from the first year field study
was harvested and screened with imazamox. Five hybrid plants
survived the initial screening indicating some out-crossing had
occurred. Seed from the second year field study was harvested and
will be screened in the winter-spring 2003. A third year field
study was planted near Lewiston, Idaho to supply additional data.
PUBLICATIONS:
Wang, Z., R.S. Zemetra, J. Hansen,
A. Hang, C.A. Mallory-Smith, and C. Burton. 2002. Determination of
the paternity of wheat (Triticum aestivum L.) x jointed
goatgrass (Aegilops cylindrica Host) BC1 plants
using genomic in situ hybridization technique. Crop Sci. 42:
939-943.
Zemetra, R.S., C.A. Mallory-Smith, J. Hansen, Z. Wang, J. Snyder, A.
Hang, L. Kroiss, O. Riera-Lizarazu, I. Vales. 2002. The evolution
of a biological risk program: gene flow between wheat (Triticum
aestivum L.) and jointed goatgrass (Aegilops cylindrica
Host). Scientific Methods Workshop: Ecological and Agronomic
Consequences of Gene Flow from Transgenic Crops to Wild Relatives.
Ohio State University, Columbus, Ohio. Pgs. 178-187.
Rehman, M., J. Hansen, R.S. Zemetra,
and C. Mallory-Smith. 2002. Estimating the risk of gene flow
between wheat and jointed goatgrass using genomic in situ
hybridization (GISH). Western Society of Crop Science Abstracts pg.
(in press)
Zemetra, R.S., C.A. Mallory-Smith, J. Brown, D.C. Thill, O.
Riera-Lizarazu, M.I. Vales, J.L. Hansen, Z. Wang, J. Snyder, and S.L.
Kunzli. 2002. Natural gene introgression between plant species:
beneficial or detrimental? Plant and Animal Genome X Abstracts.
Pg. 61.
TECHNOLOGY TRANSFER ACTIVITIES: The results of this research has
been presented at various field days (public and commercial) in
Idaho and Oregon, the Western Society of Weed Science Meeting,
Western Society of Crop Science Meeting, and as part of an invited
presentations at the Plant, Animal, and Microbe Genome meeting and
at the Scientific Methods Workshop: Ecological and Agronomic
Consequences of Gene Flow from Transgenic Crops to Wild Relatives. |