VIRGINIA
VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY
Department of Crop and Soil Environmental Sciences 1 and Department of Plant Pathology, Physiology and Weed Science 2; Blacksburg, VA 240610404, USA.
Carl A. Griffey 1, Daniel E. Brann 1, Wendy L. Rohrer 1, Jianli
Chen 1, Matthew Chappell 1, Thomas H. Pridgen 1, and Erik L. Stromberg
2.
Virginia wheat production in 1998.
W.L. Rohrer, C.A. Griffey, and D.E. Brann.
Growing conditions. The effects of El Niño were
observed in wheat fields across Virginia in 1997-98. A normal
autumn was followed by an unusually warm winter and early spring,
which was interrupted by a late and severe freeze with minimum
temperatures in the teens from 11-13 March. Heading occurred approximately
1 week earlier than usual. Lower than normal temperatures and
excessive moisture throughout most of the season resulted in high
disease pressure and, subsequently, poor test weights. The late
freeze caused significant damage to somegenotypes. Early development
of tillers and lack of significant snowfall to serve as insulation
allowed the late freeze to take its toll on the crop. Lodging
caused by heavy rains, particularly toward the end of the growing
season, also contributed to lower yields. Overall, the unpredictable
and unusual weather patterns of the 1997-98 growing season resulted
in lower than average yields and test weights across the state.
Disease incidence and severity. As mentioned previously,
the warm, wet winter of 1998 created an ideal environment for
disease proliferation. Tan spot, Septoria tritici blotch, leaf
rust, powdery mildew, take-all root rot, basal glume rot, and
scab were prevalent across the state. Many producers were made
painfully aware of the threat of disease, particularly scab, on
their ability to sell grain to elevators. Perhaps the only good
news to come from such a disease-ridden season was that researchers
were given the opportunity to evaluate differences in disease
resistance among varieties.
Production. Virginia producers harvested 245,000 acres
(99,225 ha) of soft red winter wheat for grain in 1998. Grain
yields across the state averaged 45 bu/acre (3,024 kg/ha). This
figure is 23 bu/acre (1,545 kg/ha) lower than the state yield
record set in 1997. Total grain production in 1998 was 11.0 million
bushels (299,110 metric tons).
Virginia wheat yield contests. Participation in the 1998
Wheat Yield Contest was excellent with 12 producers representing
nine Virginia counties. Yields ranged from 64 bu/acre (4,300 kg/ha)
to 97 bu/acre (6,517 kg/ha) over a minimum area of 3 acres (1.2
ha). Participants' yields were evaluated with consideration of
their respective county's average yield. Among participants, Donald
Turner of Dinwiddie County had the highest contest score yielding
91 bu/acre (6,114 kg/ha) compared with a county average of 56
bu/acre (3,763 kg/ha). Five producers representing four counties
participated in the No-Till Wheat Contest. Yields ranged from
78 bu/acre (5,261 kg/ha) to 96 bu/acre (6,457 kg/ha) over a minimum
area of 3 acres (1.2 ha). Ted Haberland of Orange County had the
highest yielding no-till wheat at 96 bu/acre (6,457 kg/ha).
State cultivar tests. A total of 58 entries were evaluated
at seven locations in Virginia in 1998. Included in the tests
were 13 experimental lines, 41 released cultivars, three wheat
hybrids, and one wheat/rye cross (triticale). Test averages for
yield ranged from 56 to 84 bu/acre (3,763 to 5,644 kg/ha) with
an overall test average of 71 bu/acre (4,770 kg/ha). Wheat genotypes
with yields significantly above the test average included Raxil/Gaucho-treated
AgriPro Patton; nine untreated experimental lines; Raxil/Thiram-treated
Pocahontas; three wheat hybrids (Raxil- treated Quantum 7203,
706, and 708); Baytan/Captan-treated AgriPro Patton and Mason;
untreated Roane; Baytan- treated Pioneer 2580; Dividend-treated
Dynagro 424; and Stine 455-V. Yields among members of this group
ranged from 74 to 84 bu/acre (4,972 to 5,644 kg/ha). Tests conducted
in the Coastal Plain Region yielded an average of 55 bu/acre (3,695
kg/ha), whereas tests conducted in the Piedmont and Blue Ridge
Region yielded an average of 84 bu/acre (5,644 kg/ha). Test weights
obtained across the seven test sites reflect the difficult growing
conditions and disease/pest pressure present throughout the growing
season. Averages ranged from 52.1 lb/bu (670.5 kg/m3) to 57.9
lb/bu (745.2 kg/m3), and the test average was 54.9 lb/bu (706.6
kg/m3). Of the 27 entries with test weights significantly higher
than the test average, seven were experimental lines, two were
wheat hybrids, and 18 were released cultivars. Virginia experimental
lines and released cultivars made up 30 % of this group. Entries
exhibiting significantly higher than average yield and test weight
included Raxil/Gaucho-treated AgriPro Patton, four untreated Virginia
experimental lines, one untreated Arkansas experimental line,
Raxil/Thiram-treated Pocahontas, two wheat hybrids (Raxil-treated
Quantum 7203 and 706), Baytan-treated AgriPro Mason, and untreated
Roane.
Cultivar release. Roane, formerly designated VA
93-54-429, was released by the Virginia Agricultural Experiment
Station in 1998. The name Roane was selected in recognition of
the contributions made by Dr. Curtis W. Roane, Professor Emeritus
of Plant Pathology, Virginia Tech, to small grains breeding and
genetics. Roane was derived as an F8 headrow that was selected
from the cross 'VA 71-54-147 / Coker 68-15 // IN65309C1-18-2-3-2'.
The final cross was made in 1984, and the population was advanced
using a modified bulk breeding method. The first two parents,
VA 71-54-147 and Coker 68-15, are also parents of the cultivar
Saluda. The parentage of the line VA 71-54-147 is 'Taylor*2 //
Norin 10 / Brevor /3/ Thorne*7 / 199-4'. The third parent, IN65309C1-18-2-3-2
(Benhur sib*2 /3/ Riley type*2 /Chancelor*5 / Khapli), was developed
by Purdue University and was obtained from the 1983 Uniform Eastern
SRWW Nursery. Roane is a full-season, high-yielding, awnleted
SRWW with exceptionally high test weight and resistance/tolerance
to a broad spectrum of plant pathogens and insect pests. Heademergence
of Roane (5 May) is similar to that of FFR 555W. Plant height
of Roane (34.5 inches) is 1 inch taller than that of Coker 9803,
1 inch shorter than that of FFR 555W, and 2 inches shorter than
that of Jackson. Roane has good straw strength, similar to that
of FFR 555W and superior to that of Jackson. Winter hardiness
of Roane is good, being similar to that of Madison and superior
to that of Jackson and Pocahontas. Over the past 4 years, the
average grain test weight of Roane was 60.0 lb/bu (772.2 kg/m
3 ), which was 2.0 lb/bu (25.7 kg/m3) higher
than the overall test average. In each of the past 4 years, the
average test weight of Roane has been 59.0 lb/bu (759.3 kg/m3)
or higher in statewide tests. Milling and baking quality of Roane
is similar to that of Pioneer 2580 and is within the quality range
of SRWW. Roane tends to be slightly softer than Pioneer 2580.
Roane is resistant to the prevalent field populations of powdery
mildew and expressed resistant reactions to 32 of 38 different
strains in seedling tests conducted at North Carolina State University.
The identity of the resistance genes in Roane is unknown, but
the cultivar may have inherited Pm3a from the parent VA
71-54-147 and Pm4a from IN65309C1-18-2-3-2. Although seedling
tests of Roane indicate that it is susceptible to many races of
leaf rust, data from field tests indicate that it has effective
resistance against some races. Roane lacks any of the known genes
for resistance to stem rust. Roane expresses an intermediate level
of resistance to WSBMV and WSSMV and to leaf and glume blotch.
Data on FHB from the 199697 Uniform Eastern SRWW Nursery and preliminary
data from research plots indicate that Roane possesses a moderate
level of resistance to scab. Roane is resistant to Hessian fly
biotypes GP, B, C, and E and is susceptible to biotypes D and
L.
In 26 tests conducted in Virginia during 1994-97, Roane had an
average grain yield of 82 bu/acre (5,510 kg/ha), which was not
significantly different from the highest yielding commercial cultivar
Pioneer 2580 at 85 bu/acre (5,711 kg/ha). In these tests, Roane
had the highest average test weight at 60.0 lb/bu (772.2 kg/m3).
Roane also has performed well in regional trials in North Carolina,
Maryland, and Kentucky. Roane was evaluated in the Uniform Eastern
SRWW Nursery grown at 27 locations in 1996 and at 29 locations
in 1997. For grain yield, Roane ranked eighth among 30 entries
over all locations and fifth over locations with low coefficients
of variability for grain yield estimates in 1996 tests. Roane
was one of two lines having the highest average test weight in
the 1996 nursery. In 1997, Roane ranked second among 33 entries
for grain yield and again had one of the highest test weight averages.
Roane is widely adapted based on 2-years performance in the Uniform
Eastern SRWW Nursery and could be recommended in most areas where
soft red winter wheats are grown. Roane's utilization in the deep
south may be somewhat limited, because it is a full-season wheat
and is moderately susceptible to leaf and stem rusts. The Virginia
Crop Improvement Association will be responsible for seed distribution
through the Foundation Seed Farm at Mount Holly, VA.
Research on Fusarium head blight in the Virginia Tech
Small Grains Program.
J. Chen, C.A. Griffey, M. Chappell, T. Pridgen, and E.L.
Stromberg
Economic importance. FHB epidemics were widespread in Virginia
in 1998, and the state yield average was 23 bu/acre (1,545 kg/ha)
lower than the record yield of 68 bu/acre (4,570 kg/ha) set in
1997. Scab epidemics are likely to become more common in the mid-Atlantic
region, because environmental conditions and production practices
favor development of the disease. High levels of resistance have
not been identified in SRWW. Therefore, the crop is at great risk,
as shown by the significant losses observed in recent years.
Germ plasm evaluation and breeding. The Virginia Tech Small
Grains Breeding and Genetics program initiated research on FHB
4 years ago. Research related to identification and incorporation
of novel germ plasm with diverse types of resistance has been
a major emphasis for the past 2 years. Among over 200 lines tested,
we have identified and confirmed high levels of type II resistance
in seven wheat lines from China, five from Canada, and two from
France. We also have identified and confirmed other types of resistance
(types IV and V) in American varieties and experimental lines.
Chinese resources such as Sumai 3, Ning 7840, W14, Shaan 85, Futai
9844, Futai 9002, and Shanghai 4 were confirmed to possess good
type II resistance. Roane, a Virginia SRWW released from our program
in 1998, has exhibited low toxin levels, good scab resistance
(types IV and V), and high yields in multistate scab nurseries.
Ernie and other SRWWs and lines have exhibited similar resistance.
To date, nearly 350 crossesinvolving scab resistant parents have
been produced. During this past year, 2,500 F5 headrows were evaluated
in an inoculated field nursery, and several F5 lines with type
II resistance and/or other types of resistance were selected and
advanced for further testing.
Scab evaluation systems and techniques. During the past
2 years, reliable protocols for testing germ plasm for resistance
to scab have been established for both greenhouse and field-testing.
Germ plasm was evaluated for type II (spike invasion) resistance
in greenhouse tests using single-floret inoculation procedures.
Data on other types of resistance (e.g., penetration, kernel infection,
and toxin production) were obtained from evaluations of germ plasm
grown in an irrigated field-nursery in which artificial inoculum
(conidia suspension and/or colonized grain) was applied two to
three times during heading and flowering stages. Scab incidence,
severity, index, kernel weight, percentage of scabby seeds, and
toxin concentration were determined to assess resistance. Correlation
analysis showed that scab severity and percentage of scabby seeds
seem to be more predictive than scab incidence for evaluating
type IV and type V resistance. The level of scab incidence may
be predictive of type I resistance, although it can be affected
by plant height, growth stage and climatic conditions under natural
infection but not with artificial inoculation. Among these assessment
parameters, selection of genotypes with a low percentage of scabby
seeds is most likely to identify plants with relatively low DON
levels.
Genetics and mapping study. The goal of this study is to
genetically differentiate identified sources of resistance so
that diverse genes can be introgressed into adapted cultivars.
A diallel cross of eight resistant and two susceptible parents
was completed in 1998 to facilitate inheritance and mapping studies.
Doubled haploids from crosses between six resistant (W14, Shaan85,
Roane, Ernie, and VR95B717) and two susceptible cultivars (Pioneer
2684 and Madison) are being developed via pollination of F1 wheat
florets with sweet corn pollen, embryo rescue, and colchicine
treatment. An F2 population of the cross 'W14/Madison' is being
characterized for type II resistance and will be used as a mapping
population.