NEBRASKA
UNIVERSITY OF NEBRASKA AND THE USDA-ARS
Department of Agronomy, Lincoln, NE 68583, USA.
P.S. Baenziger, C.J. Peterson (USDA-ARS), R.A. Graybosch (USDA-ARS),
D.R. Shelton, L.A. Nelson, D.D. Baltensperger, D.J. Lyons, G.L. Hein, R.C.
French (USDA-ARS), D.C. Stenger (USDA-ARS), T. Weeks (USDA-ARS), and J.E.
Watkins.
The 1997 Nebraska wheat crop was estimated at 70,300,000 bu, which represented
a 37 bu/A state average yield on 1,900,000 harvested acres. 2,000,000 acres
were planted to winter wheat. This crop was smaller than the 1996 crop (73,100,000
bu harvested from 2,150,000 acres with a 34 bu/A yield average) and the
1995 crop of 86,100,000 bu (41 bu/A). Despite continued genetic improvement,
the main determinant in wheat production seems to be acres harvested and
weather. Corn or other crops also may be moving increasingly into the better
wheat production areas, and the relatively stable state average wheat yield
represents the loss of these higher production acres. Arapahoe continued
to be the most popular variety (30.1 % of the state) in 1997 and was grown
on more acres in Nebraska than cultivars developed by other states and by
commercial seed companies combined.
Increase of new experimental lines.
Three experimental lines are under large-scale increase for possible release in 1998. NE93405 (NE85707/Thunderbird) is a Thunderbird derivative with a long coleoptile, good winter hardiness, good test weight, large kernels, and very strong straw strength. The pedigree of NE85707 is 'Wrr*5 / Agent // Kavkaz /4/ NE63218 / KY58 /3/ NTH / 2*CMTH // PNC / *2 CNN'. NE93405 is a white-chaffed, awned HRWW, medium early in maturity, and medium-tall in plant height (probably has a semidwarfing gene that does not affect coleoptile length). In the first year of testing in the state variety trial, its grain yield (47.3 bu/A) was less than those of Alliance (50.6 bu/A), Arapahoe (48.9 bu/A), Niobrara (49.3 bu/A), and Windstar (50.6 bu/A). The best performance area seems to higher moisture areas of Nebraska similar to Thunderbird. The relatively lower statewide performance of NE93405 compared to many widely grown cultivars probably represents its narrower adaptation, and many of the testing sites are outside of its adapted area. NE93405 is moderately resistant to stem rust (contains Sr5 and Sr31 or Sr24); moderately susceptible to leaf rust; and susceptible to Hessian fly, BYDV, WSBMV, and WSMV. A sister line, NE93496, may be a slightly higher yielding line and could be released in 1999.
NE93554 was derived from the cross 'NE82419 / Arapahoe'. The pedigree of NE82419 is 'Trapper // CMN / OT /3/ CIMMYT / Scout /4/ Buckskin sib / Homestead'. NE93554 is an Arapahoe derivative with a medium-length coleoptile, good winter hardiness, average test weight, medium kernels, and moderately strong straw strength. NE82419 is a white-chaffed, awned HRWW. NE93554 is medium in maturity and medium tall in plant height (probably a taller, semidwarf). In the first year of testing in the state variety trial, its grain yield (50.7 bu/A) was similar to that of Alliance (50.6 bu/A) and Windstar (50.6 bu/A), and better than that of Arapahoe (48.9 bu/A) and Niobrara (49.3 bu/A). NE93554 seems adapted to all of the areas where Arapahoe has been successfully grown. Though it yielded better than Arapahoe, NE93554, like Arapahoe, also seemed to have a growth pattern where early spring drought can lower its performance. NE93554 is moderately resistant to stem rust (contains Sr6 and Sr36 and other unnamed resistance genes) and leaf rust (similar to Arapahoe); moderately susceptible to WSBMV; and susceptible to Hessian fly, BYDV, and WSMV. A sister line, NE93613, also is being advanced for possible release in 1999.
NE93427 was derived from the cross 'Bez / CTK78 // Arthur / CTK78
/3/ Bennett /4/ Norkan'. NE93427 is a Norkan derivative with a medium-length
coleoptile, medium winter hardiness, good test weight, medium kernels, and
moderately strong straw strength. The line is a white-chaffed, awned HRWW,
medium early in maturity, and medium tall in plant height (probably a taller
semidwarf). In the first year of testing in the state variety trial, its
grain yield (47.6 bu/A) was less than those of Alliance (50.6 bu/A), Arapahoe
(48.9 bu/A), Niobrara (49.3 bu/A), and Windstar (50.6 bu/A). NE93427 seems
best adapted to the higher rainfall areas of southeastern and south central
Nebraska near the Kansas border, an area where few of our previous releases
are well adapted. The relatively lower statewide performance of NE93427
compared to many widely grown varieties probably represents its narrower
adaptation, and many of the testing sites are outside of its adapted area.
NE93427 is moderately resistant to stem rust (contains Sr5, Sr6,
and Sr24) and WSBMV; moderately susceptible to leaf rust; and susceptible
to Hessian fly, BYDV, and WSMV.
Winter triticale breeding.
We continue a small winter triticale breeding effort. Triticales with high grain and forage-yield potential have been identified and may be useful as a feed grain or forage crop. Forage triticale is our main effort because annual forages are needed for our livestock industry and seedsmen like them, because the farmers save less seed. The grain triticales continue to perform well, but currently the market is limited.
Wheat transformation and gene expression efforts.
A team of scientists (A. Mitra, J. van Etten, R. French, P. Staswick, J.
Morris, T. Elthon, P. Blum, K. Gill, and S. Baenziger) at the University
of Nebraska has developed a major effort on gene expression in plants with
an emphasis on wheat and soybean transformation. In wheat, the key goals
for transformation will be disease and stress (mainly heat) resistance.
As part of this effort and those of the Biotechnology Center, a new Biotechnology
Core Facility on Plant Transformation was developed with Dr. Tom Clemente
as the facility coördinator.
The wheat transformation efforts are led by Ms. Shirley Sato, formerly
with Monsanto. Using particle bombardment, we have produced 194 plants that
were confirmed transgenic by either GUS assay, nptII leaf bleach, or nptII
ELISA. These 194 plants represent 130 independent transformation events.
Thirteen more putative transformants representing eight independent events
are awaiting verification (leaf bleach and ELISA) when they have grown.
Transformation using the particle gun is routine. Experiments also were
initiated to develop a routine transformation system using Agrobacterium
tumefaciens. We have produced a few transgenic plants by this method,
but additional improvements will be needed before it is used routinely.
Dr. Jai-hoen Lee and Mr. Kamil Haliloglu, in cooperation with Ms. Sato and
Dr. Clemente, are conducting research on optimizing the Agrobacterium-mediated
transformation of wheat. Drs. Mitra, Clemente, and Ms. Sato have incorporated
genes for viral, fungal, and bacterial resistances in wheat. Mr. Todd Campbell
is beginning to study the expression and inheritance of the wheat viral
resistance transgene. We also have looked at optimizing the culture conditions
for the transformation of Bobwhite, the main wheat used in transformation
(work done by Dr. Jan Rybczynski, a Fulbright visiting professor, and Mr.
Kim Kyung-Moon).
Chromosome substitution lines.
Mr. Mohammed Maroof Shah completed the data analysis of the field evaluations of the recombinant inbred chromosome lines (RICLs) for Cheyenne (CNN)Wichita (WI) chromosome 3A lines. As in our previous studies, CNN (WI3A) had significantly higher grain yield and kernel weight than CNN. CNN (WI3A) also was significantly earlier flowering than CNN. The parent lines were not different from each other for grain volume weight. Hence, the QTLs for grain yield on chromosome 3A, despite having a significant 'G x E' interaction, have been identified in eight, four, and now in seven environments.
Significant differences were identified among the RICLs for those traits
for which the parent lines were significantly different, which indicate
that the parental QTLs are segregating among the RICLs. The RICLs appeared
to have relatively little statistically significant transgressive segregation,
which can be interpreted as the parent lines differing by one gene or by
genes in coupling phase. The frequency distributions were tested for normality,
and all of the distributions were statistically normal. However, when we
looked at the frequency distributions, anthesis date appeared to be bimodal
with the peaks being similar the parental values. When anthesis dates were
grouped by the parental values, a chi-square test indicated 1:1 segregation,
which we interpreted as single gene segregation. Visual evidence of bimodality
also was observed for plant height and 1,000-kernel weight in some environments,
whereas grain yield, kernels/tiller, tiller/m2, and grain volume weight
were visually normally distributed. A significant correlation was found
between anthesis date, plant height, and 1,000-kernel weight. Most of the
early flowering and short-stature lines were generally similar to CNN (WI3A)
for 1,000-kernel weight, whereas most of the late flowering and taller lines
were similar to CNN. However, two lines had plant heights similar to CNN
(WI3A) but were as late as CNN, which we believe indicates crossing over
between the gene controlling anthesis date and the gene(s) or QTLs for plant
height or a second segregating gene. Larger 'G x E' effects for yield and
its component traits, kernels/tiller and tiller/m2, and for grain volume
weight may be the reasons of not detecting major genes for these traits.
A second goal of this research was to screen for polymorphic molecular markers
on chromosome 3A, so that we can map the regions of chromosome 3A that contain
gene(s)/QTLs affecting these important agronomic traits. The screening was
initiated in coöperation with Dr. Kulvinder Gill, molecular cytogeneticist
at the University of Nebraska, and Dr. Yang Yen, a biochemical cytogeneticist
at South Dakota State University. Of the 51 RFLP probes we were able to
test in our initial screens, 78 % detected polymorphism between CNN and
WI with one or more of the seven restriction enzymes, 43 % detected polymorphism
for chromosome 3A,and 66 % probes were found polymorphic for chromosomes
3B or 3D. The average RFLP frequencies detected per restriction enzyme for
3A, 3B/3D, and for the whole group 3 chromosomes were 13.8, 30.3, and 22
%, respectively. This high level of RFLP polymorphism between these cultivars
was unexpected and may be somewhat fortuitous. Dr. Gill also is interested
in looking at recombination in group-1 chromosomes, and the level of polymorphisms
does not appear to be as high as for group-3 chromosomes. These results
(and those described below for SSRs) indicate it should be possible to construct
a reasonably dense map of chromosome 3A. Using Mapmaker Macintosh 3.0, we
were able to develop a tentative map of our RFLP probes. Using single factor
analysis of variance followed by stepwise regression, we were able to tentatively
map some of the QTLs controlling our traits. Affiliations of anthesis date
with plant height and kernel weight were found and are of particular interest.
It will useful to know if the traits are linked (as our empirical data seem
to indicate), pleiotropic, or affected by different secondary genes. In
dryland winter wheat production, anthesis date is often critical for determining
grain yield, because it is a main factor in how the plants respond to sporadic
rains during the grain-filling period.
A total of 135 PCR primer sets were screened for polymorphisms. Of the
68 STS primer sets screened, three (E14, ABG57.1, and ABG471 ) generated
polymorphisms between WI and CNN, but only one (ABG471) generated a DNA
fragment of about 800-bp that showed polymorphisms between CNN3A and WI3A.
A total of 40 RAPD primer sets were screened, and only eight were able to
generate polymorphism between WI and CNN. However, none of the eight primer
sets generated a polymorphism between CNN 3A and WI 3A. Of the 35 SSR primer
sets screened, six generated polymorphisms between CNN and WI, of which
five (WMS30, WMS114, WMS155, WMS369, and Xpsp3047) generated polymorphisms
between CNN 3A and WI 3A. This preliminary screening indicated that for
us, SSRs might be the most useful PCR-based molecular markers. Therefore,
our future screening efforts for PCR-based markers will be focused more
on SSR markers. We thank those who have provided probes and primers for
this research.
The effect of T1A·1R on agronomic performance.
Previously, Dr. Benjamin Moreno-Sevilla, now with HybriTech, had shown that lines containing T1BL·1RS from the cross 'Siouxland / Ram' were 9 % higher yielding than lines with 1B or lines heterogeneous for T1BL·1RS, but that T1BL·1RS and 1B lines derived from the heterogeneous cultivar Rawhide (a variety containing 1B and T1BL·1RS plants) were not different for grain yield. The T1AL·1RS translocation was reported similarly to enhance grain yield. A replicated study conducted by Dr. Eduardo Espitia-Rangel, a former graduate student, using Nekota (a heterogeneous variety for 1A and T1AL·1RS) was completed to determine if T1AL·1RS has beneficial effects for yield and detrimental effects on end-use quality. Dr. R.A. Graybosch (USDAARS) helped identify which lines contain the rye translocation. The presence of T1AL·1RS translocation in the Nekota background increased kernel weight (3.3 %) and grain volume weight (0.4 %), had no effect on grain yield, kernels/spike, and anthesis date, and decreased plant height (1.2 %) and spikes per square meter (2.9 %). The 1A and T1AL·1RS were equally stable for grain yield, kernels per spike, spikes per square meter, and plant height. For kernel weight, the 1A lines were more responsive and tended to have heavier kernels under favorable environments, whereas the T1AL·1RS lines had heavier kernels under less favorable environments. For grain volume weight, the 1A lines were more responsive than the T1AL·1RS lines, which had heavier grain volume weight under less favorable environments.
The presence or absence of the T1AL·1RS translocation produced
significant differences for all the end-use quality traits. The presence
of T1AL·1RS translocation increased flour protein (4.3 %) and decreased
flour yield (2.3 %), Mixograph mixing time (from 2.9 to 2.7 min), and Mixograph
mixing tolerance (from 3.5 to 3.1). Despite higher flour protein in T1AL·1RS
lines, the 1AL·1RS translocation was not beneficial for end-use quality
traits. The 1A and T1AL·1RS lines had similar stability values for
flour yield and flour protein; the 1A lines showed higher flour yield in
all environments, whereas the T1AL·1RS lines had higher flour protein
in all environments. For mixing tolerance and mixing time, the 1A lines
were more responsive to the environment, whereas the T1AL·1RS lines
had exceptional stability over all environments. Although high levels of
stability (uniformity) are desired by the milling and baking industry, the
stable T1A·1R lines were uniformly poor quality in every environment.
The end-use quality of Nekota can be explained by a mixture of 1A lines
with good quality and T1AL·1RS lines with poor to good quality. The
1A composite had improved end-use quality compared with Nekota; however,
the end-use quality was still barely acceptable.
An interesting aspect of this research was that both Nekota and Niobrara,
heterogeneous cultivars for 1A and T1A·1R, consisted of mainly 1A
genotypes. The frequency of T1AL·1RS lines was less than 25 %.
Global change research.
One of the new areas that the project hopes to become involved in is
global change scenarios. An interdisciplinary effort involving crop modeling
(Dr. A. Weiss); crop physiology and production (Dr. T. Arkebauer, Dr. J.
Maranville, Dr. Drew Lyon, and Dr. Madhavan); cereal chemistry (Dr. D. Shelton);
biometrics (Dr. K. Eskridge); economics (Dr. G. Helmers); and plant breeding
(Dr. Baenziger) was formed. The goal of this group will be to develop experimental
techniques that will allow us to predict what may occur under various global
change scenarios (e.g., global warming or elevated CO2) and to identify
germplasm that may ameliorate these changes. We are currently building at
Mead field chambers to study enhanced CO2 and warming scenarios. Too often,
plant breeding is reactive and not sufficiently proactive. With the 12-year
time frame needed to release a cultivar, wheat breeding programs need to
be as cognizant as possible of future changes. Although this may seem future
oriented, it should be recognized that with the variable climate of Nebraska,
many of the possible scenarios (e.g., drought or heat stress, or rapid weather
change) occur annually in one or another part of the state, so the effort
will be to develop an integrated team that will understand wheat production
at the ecosystem level.
Spring-sown wheat research.
A small spring-sown wheat breeding effort was initiated in 1997. The
purpose of this research is provide producers with an additional adapted
crop for their rotations. Winter wheats with low vernalization response
could be ideal for spring sowing.
Wheat quality genetics research.
R.A. Graybosch and C.J. Peterson, USDA-ARS.
Quality effects of 1RL in wheat. Investigations of the end-use quality effects of alien genes and naturally occurring mutations were conducted in wheat. Quality effects of rye chromosome arm 1RL transferred to wheat were characterized by comparison of a group of 1R(1B) substitution lines and T1BL·1RS translocation lines. The experimental materials were sister lines derived from the cross 'Mironovskaya10 / NE7060 // NE80413'. 1R(1B) substitution lines were identified by the presence of rye omega- and gamma-secalins among 70 % ethanol-soluble proteins combined with the presence of HMW-secalin proteins in total grain protein extracts. Genes on 1RL reduced grain weight, grain hardness, mixograph time, mixograph tolerance, and SDS-sedimentation volumes. 1RL had no effect on flour yield or grain protein concentration but did elevate flour protein contents. The HMW-secalin proteins encoded by genes on 1RL most likely caused the decline in dough strength seen in 1R(1B) lines relative to that of T1BL·1RS sister lines. Reduced grain hardness also might be related to the presence of HMW secalins, although a role for additional, unidentified genes on 1RL could not be discounted. The diminished dough strength characteristics of 1R(1B) lines argue against the deployment of 1R in wheat breeding programs, unless rigorous selection for dough strength is exercised.
Frequency of 1RS in advanced winter wheat breeding lines. USDAARS Regional Wheat Performance Nurseries were screened for the presence of wheats carrying chromosome arm 1RS. Combined frequencies of T1AL·1RS and T1BL·1RS lines in each nursery were: Eastern SRWW, 22.6 %; Southern SRWW, 30.3 %; Northern Regional Performance Nursery, 20.0 %; Southern Regional Performance Nursery, 33.3 %; and Western Plains Nursery, 17.9%.
Null mutations in genetic loci encoding the wheat granule-bound starch
synthase (GBSS or waxy protein). Amylose contents of biotypes of Norin-1
possessing null alleles at two wx loci were found to be significantly
lower than those of biotypes with only one null allele. Therefore, the creation
of double null lines is a more effective means of developing wheats with
reduced starch amylose content. Wheats carrying two GBSS null alleles are
rare among the U.S. gene pool. Only one such wheat, the HRWW cultivar Ike
has been released to date. A survey of breeding lines derived from Ike was
conducted and resulted in the identification of 35 additional double null
lines. Characterization of the starch pasting properties of these lines
has demonstrated a significant increase in starch pasting viscosity associated
with the presence of two null alleles. These double null wheats will be
useful in the development of wheats with starch properties more suitable
for Asian wet noodle production.
Wheat streak mosaic virus nucleotide sequence and phylogenetic
relationships.
Drake C. Stenger and Roy French, USDA-ARS.
The complete nucleotide sequence of WSMV has been determined. The WSMV
genome consists of 9,384 nucleotides encoding a single polyprotein of 3,035
amino acid residues. The WSMV polyprotein contains proteinase cleavage sites
predicted to be cleaved by viral-encoded proteinases, thereby giving rise
to mature protein products typical of a plant potyvirus. Phylogenetic studies
indicate that WSMV is related most closely to another eriophyid mite-transmitted
potyvirus, brome streak mosaic virus (BrSMV). In contrast, WSMV and BrSMV
are not related closely to another eriophyid mite-transmitted potyvirus,
ryegrass mosaic virus (RGMV). Instead, RGMV shares a most recent common
ancestor with aphid-transmitted potyviruses. These results indicate that
the eriophyid mite-transmitted potyviruses evolved as two separate lineages,
suggesting that a revision of the taxonomic status of eriophyid mite-transmitted
potyviruses is necessary. This initial characterization of the WSMV genome
forms the basis for current studies aimed at understanding the mechanisms
by which WSMV induces disease in wheat and also will facilitate efforts
to obtain genetically engineered wheat varieties with improved resistance
to WSMV.
Personnel.
Mr. Mehmet Atak completed his M.S. degree and returned to his university in Turkey. Dr. Eduardo Espitia-Rangel completed his Ph.D. and returned to Mexico as part of the national dryland spring wheat breeding effort. Dr. Jai Hoen Lee accepted a position in Korea as a university professor and returned to Korea. Dr. Mohammed Maroof Shah completed his Ph.D. and accepted a postdoctoral position working on alfalfa molecular genetics at Iowa State University.
Dr. Drake Stenger joined the USDA-ARS Wheat, Sorghum, and Forage Unit
as a Research Virologist. Dr. Stenger's research will focus on the molecular
biology and control of WSMV infections in wheat.
Publications.
Baenziger PS, Moreno-Sevilla B, Peterson CJ, Shelton DR, Baltensperger
DD, Nelson LA, McVey DV, Watkins JE, Hatchett JH, and Schmidt JW. 1997.
Registration of 'Pronghorn' Wheat. Crop Sci 37:1006.
Baenziger PS. 1997. Reflections on doubled haploids in plant breeding. In:
In vitro haploid production in higher plants, Vol. 1: Fundamental
aspects and methods (Jain SM, Sopory SK, and Veileux RE eds). Kluwer Academic
Publishers, Norwell, MA, U.S. pp.35-48.
Graybosch RA and Peterson CJ. 1997. Granule-bound starch synthase of wheat:
effects of gene dosage and allelic composition. Cereal Foods World 42:669.
Graybosch RA, Peterson CJ, Hansen LE, Hill A, and Skerritt J. 1997. Occurrence and expression of granule-bound starch synthase mutants in hard winter wheat. In: Starch Structure and Functionality (Frazier PJ, Donald AM, and Richmond P eds). The Royal Society of Chemistry, Cambridge, UK. pp. 214-221.
Graybosch RA, Peterson CJ, Hansen LE, Rahman S, Hill A, and Skerritt J. 1998. Identification and characterization of U.S. wheats carrying null alleles at the wx loci. Cereal Chem 75:162-165.
Lee JH, Arumuganatha