S.D. Haley, R.A. Schut, F. Hakizimana, and Z. Zhang.
Production. Winter wheat
production in South Dakota in 1995 was estimated at 56.2 million
bushels from 1.52 million harvested acres (1.6 million planted
acres), for an average of 37 bushels/acre. This yield level was
16 % more than the 1994 crop (32 bushels/acre) and 9 % more than
the average of the previous 5 years (34 bushels/acre). Total production
was the third highest on record, slightly less than that of the
1993 (56.5 million bushels) and 1986 (57.6 million bushels) crop
years. The high level of production experienced in 1995 was due
largly to an extremely mild winter and a very low level of winterkill
throughout the state, because planted acreage has not increased
in the last 5 years (previous 5-year average is 1.63 million acres).
In fact, in 1995, the preharvest acreage losses (expressed as
the percent difference between planted and harvested acreage)
was only 5 %, compared to the 15 % average loss experienced over
both the previous 5- and 10-year periods.
In spite of the low level of winterkill and high
production, the winter wheat crop was perhaps still one of unrealized
expectations. In most areas, good soil moisture was available
at planting and excellent autumn stands were realized. An extremely
mild autumn provided excellent (actually excessive, with some
early plantings) crop growth going into winter. However, these
same mild temperatures allowed cereal aphids (most importantly,
the bird cherry-oat aphid) to feed well into December. As a result
of such aphid infestations, BYDV was observed throughout the winter
wheat area in the following spring. In some fields, severe `yellowing'
was reported that was not a direct result of BYDV infection.
Although this was initially confused with early tan spot infections,
which were quite severe in `stubble-back' plantings,
much of the yellowing reported was due to the combined effects
of waterlogging and nitrogen leaching that resulted from excessive
spring rains.
Two periods of unusually hot weather also adversely
affected production (mid-June and early-July). Many of the early-maturing
varieties effectively escaped the effects of the high temperature,
because they had already reached heading before the first hot
spell and were nearing maturity when the second hot spell arrived.
However, many later-maturing varieties were affected much
more severely. Wet and cool spring weather (that unfortunately
also hindered spring wheat planting) retarded crop development,
so that the heading of later-maturing varieties coincided with
the mid-June hot spell. The early-July hot spell effectively
prevented proper grain filling of such later-maturing varieties
that already had been affected adversely at heading.
Breeding program. In
1995, the winter wheat breeding program conducted testing at 10
sites throughout South Dakota. These environments included both
Aurora and Brookings (Brookings Co.), Highmore (Hyde Co.), Selby
(Walworth Co.), Winner (Tripp Co.), Wall (Pennington Co.), and
both irrigated and dryland environments at the Dakota Lakes Research
Farm east of Pierre (Hughes Co.). In addition to these testing
sites, additional testing sites were added for the South Dakota
Advanced Yield Trial (AYT) in 1995 at Bison (Perkins Co., in cooperation
with Clair Stymiest and John Rickertson, SDSU West River Agricultural
Research and Extension Center, Rapid City) and at the Northeast
Research Farm near Watertown (Codington Co.). Both of these testing
sites were added to potentially provide more reliable winterhardiness
data on materials at various stages in the program.
During the summer of 1995, needed improvements were
made to the greenhouse facility (funded by the South Dakota Crop
Improvement Association and the Foundation Seeds Stocks Division).
The improvements included installation of an evaporative pad
cooling system (cooling pads and exhaust fans) and high pressure
sodium lighting. Together, these will improve the effectiveness
of our greenhouse program by ensuring greater seed production
from crosses and F1 increases and allowing crossing and increase
of elite/elite F1 cross combinations in a single year.
New releases and preliminary increases.
A new cultivar, named `Pronghorn', was released
for autumn 1995 planting. Pronghorn was developed by the University
of Nebraska and released cooperatively with the USDA-ARS
and Agricultural Experiment Stations in South Dakota and Wyoming.
Pronghorn was derived from the cross `Centura/Dawn//Colt
sib' made by the University of Nebraska Wheat Breeding
Program in 1982. Pronghorn was tested as NE88584 in the Southern
Regional Performance Nursery (SRPN) in South Dakota from 1992-93
and in the South Dakota Crops Performance Testing (CPT) Variety
Trial in 1995. Although statewide testing in South Dakota was
somewhat limited prior to its release, Pronghorn has performed
quite favorably compared to agronomically similar varieties currently
under production in South Dakota.
Pronghorn is a medium-early (1 day earlier than
Arapahoe, similar to both Scout 66 and Sage), tall wheat (1 inch
shorter than Roughrider, similar to both Sage and Scout 66, 2
inches taller than Arapahoe) with good winter hardiness (similar
to Arapahoe) and a long coleoptile (longer than that of Arapahoe,
but slightly shorter than that of both Scout 66 and Sage). Pronghorn
is susceptible to wheat streak mosaic virus, moderately resistant
to stem rust, moderately susceptible to leaf rust, and moderately
susceptible to both tan spot and Septoria leaf spot. Under South
Dakota environments, Pronghorn has shown very good grain protein,
test weight, and kernel weight characteristics. Straw strength
of Pronghorn is considered only moderate, but greater than that
of both Scout 66 and Sage.
Three advanced experimental lines were placed under
small scale increase for fall 1995 planting. These three lines,
SD89119 (Brule/Agate), SD89153 (TAM 105/Winoka), and SD89205 (Centura/Dawn),
have shown promise in regional or statewide trials between 1993
and 1995. Statewide and regional testing data obtained in 1996
will determine the ultimate potential of these lines for release
(earliest possible release fall 1997).
Barley yellow dwarf virus and bird cherry-oat
aphid. Because both the bird cherry-oat
aphid (BCO) and barley yellow dwarf virus are endemic problems
in South Dakota, we have initiated efforts to incorporate resistance
to both of these pests. Working collaboratively with Dr. Stephen
Baenziger (University of Nebraska, Lincoln), Dr. Bob Kieckhefer
(USDA-ARS-NGIRL, Brookings), and Dr. Marie Langham
(SDSU), we evaluated wheat progenies with resistance to BYDV transferred
from intermediate wheatgrass. Continuing the work with Dr. Kieckhefer
and Dr. Walt Riedell (USDA-ARS-NGIRL, Brookings),
we began to evaluate critically five wheat lines (three from Hungary
and two from Iran) that were reported previously to carry some
form of resistance to BCO. Research on both of these topics will
continue as capabilities allow.
Wheat curl mite. Dr.
Bob Collins, a research entomologist in the Plant Science Department,
has begun to rear colonies of the wheat curl mite, the vector
of wheat streak mosaic virus. Working collaboratively with Dr.
Marie Langham, Dr. Collins is trying to determine the potential
of controlled populations of the wheat curl mite to overcome resistance
in two new wheat lines that reportedly have higher levels of resistance
than previous resistant sources. Because the wheat curl mite
can `adapt' to or overcome other sources of resistance,
this information will be very useful to help us determine the
potential for the new resistance sources.
Coleoptile length. A
graduate student, Mr. Frederick Hakizimana, is continuing thesis
research on various aspects of coleoptile length measurements.
Using field- and greenhouse-grown seed samples from nurseries
conducted in 1994 and 1995, his research will aim to determine
the extent of environmental influences and `genotype x environment'
interactions on coleoptile length measurements. A secondary objective
of his research will be to characterize a large collection of
Great Plains winter wheat germplasm for coleoptile length and
to identify both standard-height lines with short coleoptiles
and semidwarf germplasm with long coleoptiles.
Leaf spotting diseases.
A new graduate student, Ms. Xiuling Zhang, joined the program
in January, 1996. Working collaboratively with the new small grain
pathologist, Dr. Yue Jin, Ms. Zhang will conduct thesis research
focusing on both tan spot and Septoria leaf blotch. Research
projects will aim at refining greenhouse screening procedures
and evaluate the genetic control of several promising sources
of resistance to both of these diseases.
M.A.C. Langham, K. Compton, and X. Wu.
During the spring of 1995, an unusual number of winter
wheat fields exhibiting circular patterns of stunting, yellowing,
and reduced root growth were observed in central and western South
Dakota. Plants from these areas reacted positively in ELISA tests
for the PAV strain of BYDV. Over one-third of all winter wheat
fields tested in routine diagnostic analysis were positive for
the BYDV-PAV isolate. High populations of Rhopalosiphum padi
L. were noted on young winter wheat by entomologists during the
autumn of 1994 and probably were responsible for the increased
incidence of BYDV in 1995.
W. Riedell and R. Kieckhefer (USDA-ARS-NGIRL).
Barley yellow dwarf virus reared its ugly head in
South Dakota during the 1994-95 winter wheat growing season.
The long, mild autumn of 1994 probably helped populations of the
bird-cherry oat aphid (Rhopalosiphum padi L.), a known
vector of BYDV, to proliferate in the autumn-planted cereal crop.
In response to this changing BYDV epidemiology, cooperative studies
between scientists from the SDSU Ag Experiment Station and the
USDA Agricultural Research Service were initiated. The goals
of these projects were to determine the amount of BYDV-induced
yield loss in winter wheat varieties popular in South Dakota,
and to determine the impact of crop production practices (planting
date and soil fertility) on plant response and yield loss. Studies
initiated included: investigation of the impact of BYDV infection
and R. padi infestation on root and shoot growth and development
and yield components in field-grown spring wheat Sharp; investigation
of BYDV and R. padi damage imposed before vernalization
on yield components of Roughrider, Norstar, TAM 107, and Vona
winter wheat varieties grown in the greenhouse; and investigation
of BYDV and R. padi damage imposed before vernalization
on root and shoot growth and development in TAM 107 and Arapaho
winter wheat grown in the field. Additional studies of the possibility
of using remote sensing to detect BYDV outbreaks are also planned.
Soil fertility and production research.
H. Woodard, A. Bly, and D. Winther.
An experiment was conducted at the Crop Improvement
Association farm in Aurora, SD, to investigate the effect of a
late-season foliar N application on grain yield and protein of
hard red winter wheat and hard red spring wheat varieties. Liquid
fertilizer N was applied across the entire experiment as 28-0-0
at recommended rates by an applicator knife set at 12-inch spacings
and perpendicular to the intended planted rows to support a yield
goal of 50-60 bu/acre. No tillage operation was performed
on the field, which was fallowed during all of 1994. Seeds of
15 HRWW and HRSW varieties were planted with a no-till drill on
23 September, 1994, and on 25 April, 1995, respectively. Treatment
plots 5-ft wide and 40-ft long were seeded at a rate of 1.2 million
live seeds/acre. At least three varieties were selected from
each of the early, mid-, and late-maturity groups. Fertilizer
P was applied together with the seed as 0-46-0 at the recommended
rate of P2O5/acre. Herbicides (Hoelon, Buctril, and MCP-ester)
were applied postemergence as required to control weeds. Later
in the growing season, a N solution was applied as a foliar spray
onto half the treatment plots after anthesis (Feeke's stage 10.53)
by a conventional 5-ft sprayer equipped with a protective spray
hood to prevent drifting. The N solution was applied at a 20
gal/acre rate of a 1:1 solution of 28-0-0 (UAN):water to
provide 30 lbs N/A. Treatment combinations were replicated four
times in a factorial design. Grain was harvested by small plot
combine, cleaned, and weighed for yield determination. Samples
of grain were used to measure test weight and crude grain protein
concentration.
Grain yield for HRWW varieties ranged from 50 to
65.6 bu/acre and grain protein concentration ranged from 11.8
to 14.1 % across all treatments combinations. Grain test weight
was greatest in the late maturing HRWW varieties and lowest in
the early maturing varieties. Grain yields ranged from 37.8-47.8
bu/acre for the HRSW varieties, and grain protein content ranged
from 12.4-14.7 % across all treatments combinations. Grain
yield was lowest for the mid-maturing HRSW varieties and greatest
for the late varieties. After the foliar N application, grain
protein concentration increased 0.9 % above that of the control
plots for HRWW varieties and 0.6 % above that from the untreated
plots for HRSW varieties. Grain yield was greatest in the mid-maturing
HRWW varieties, and grain protein concentration was greatest in
the early maturing varieties. Grain protein was lowest for the
late-maturing HRSW wheat varieties and greatest for the mid-maturing
varieties. Growing conditions were generally favorable, but leaf
rust infected some HRWW varieties in the later part of the growing
season.
S. Clay, J.F. Gaffney, and L.J. Wrage.
Trifluralin is used for weed control in wheat, but
may reduce vegetative growth and yield. Postemergence (POST)
herbicides may cause additional plant stress to trifluralin-stressed
wheat. Field studies at Groton, SD, in 1991 and 1992, and at
Highmore, SD, in 1992, evaluated the effects of 2,4-D-amine, difenzoquat,
metsulfuron, and a combination of `fenoxaprop-ethyl + 2,4-D-ester
+ MCPA-ester' on hard red spring wheat cultivars 2375,
Prospect, and Butte 86 seeded in areas treated with preplant incorporated
trifluralin either in the spring before seeding (0.56 kg ai/ha)
or the previous year (1.12 or 2.24 kg ai/ha). Trifluralin, applied
in the spring and followed by some POST herbicides, reduced shoot
dry weight and grain yield. Trifluralin reduced the yield of
Prospect the most and that of 2375 the least. Yields of trifluralin-treated
wheat were reduced 23% by metsulfuron and 14 % by `fenoxaprop-ethyl
+ 2,4-D + MCPA' compared to yields of wheat treated with
only the respective POST herbicide. Yields were not reduced with
any trifluralin-POST herbicide combination when trifluralin was
applied a year prior to seeding wheat.
Publications.
Clay SA, Gaffney J, and Gaffney LJ. 1995. Spring
wheat cultivar responses to trifluralin and postemergence herbicides.
Weed Tech 9:352-355.