NEBRASKA
UNIVERSITY OF NEBRASKA AND THE USDA-ARS
Department of Agronomy, Lincoln, NE 68583, USA.
The 1999 Nebraska wheat crop was estimated at 86,400,000 bu,
which represented a state average yield of 48 bu/acre on 1,800,000
harvested acres. This yield is excellent for Nebraska and represents
generally favorable growing conditions (above-average moisture,
no winterkill, and only pockets of drought and heat) and few diseases
in the main growing regions. Arapahoe continues to be the most
popular and widely grown variety (25.0 % of the state).
New cultivars.
Three new cultivars, Cougar, Millennium, and Nuplains, were recommended formally for release in 1999. Cougar is a HRWW cultivar developed coöperatively and jointly released by the Nebraska Agricultural Experiment Station and the USDA-ARS. Cougar was selected from the cross 'NE85707/Thunderbird'. The pedigree of NE85707 is WRR*5/Agent//Kavkaz/4/ NE63218/KY58/3/ NTH/2*CMTH//PNC/*2 CNN. Cougar was released primarily for its very long coleoptile (similar to Scout 66) with exceptional straw strength (superior to 2137 and Wesley). The variety has excellent test weight and kernel size. Similar to Thunderbird, its yield level is lower except where its coleoptile length and standability are needed.
Cougar is an awned, white-glumed cultivar. The field appearance of Cougar is most similar to that of Thunderbird and Big Dawg. Cougar was tested as NE93496 in Nebraska yield nurseries starting in 1994. In 2 years of testing in Nebraska cultivar performance trials, it has performed competitively in the southeast, southcentral, and southwestern Nebraska, areas where historically Thunderbird also performed well. In this region (17 environments), Cougar had a yield of 4,100 kg/ha, which was lower than those of Wesley (4,700 kg/ha) and 2137 (4630 kg/ha) but superior to that of Pronghorn (3,820 kg/ha), the only other modern, long-coleoptile wheat in the trial. The main advantages Cougar has compared to most other available wheat cultivars within its area of adaptation are its long coleoptile, exceptional straw strength, good grain volume weight and kernel size, and competitive grain yields.
Cougar is medium-early in maturity, with flowering about 1 day earlier than Arapahoe, similar to Alliance, and 1 day later than Pronghorn. Cougar has a long coleoptile, similar to those of Scout 66 and Pronghorn and longer than those of Arapahoe, Alliance, and Wesley. The mature plant height of Cougar (90 cm) is 3 cm taller than that of Arapahoe, but 7 cm shorter than that of Pronghorn. Cougar is very strong strawed, equal to or better than the strongest-strawed cultivars currently grown in Nebraska. The winter hardiness of Cougar is good to very good and comparable to that of other winter wheat cultivars adapted and commonly grown in Nebraska.
Cougar is moderately resistant to stem rust (contains Sr31 and possibly Sr24), moderately susceptible to leaf rust (contains Lr26 and possibly Lr24), and susceptible to WSBMV, Hessian fly, BYDV, and WSMV. Cougar has excellent grain-volume weight (77.9 kg/hl), higher than those of Alliance, Arapahoe, Niobrara, and Pronghorn. The milling and baking properties of Cougar were determined for 5 years by the Nebraska Wheat Quality Laboratory. The average wheat protein content of Cougar (13.3 %) was higher than those of Arapahoe (12.8 %) and Scout 66 (12.5 %). The average flour extraction on the Buhler Laboratory Mill for the Cougar (71.8 %) was similar to that of Arapahoe, but less than that of Scout 66. The flour ash content was slightly higher than the check varieties. The average flour protein content (12.1 %) was higher than that of the check varieties. Dough mixing properties of Cougar were less than those of Arapahoe and stronger than those of Scout 66. Average baking absorption (60.8 %) was less than those of the check varieties. The average loaf volume of Cougar was greater than that of the checks. The scores for the internal crumb grain and texture were generally good, though slightly more variable, which were slightly less than those of Arapahoe and Scout 66. The slightly higher variability in crumb grain and texture in Cougar is most likely due to its being homogeneous for the T1B·1R translocation. Despite the presence of the T1B·1R translocation, the overall end-use quality characteristics for Cougar should be acceptable to the milling and baking industries.
Cougar should be well adapted to most dryland wheat production systems where a dry seed bed requires planting to moisture and to conditions of high fertility or moisture, which require superior straw strength. With its lower yield potential, it is not recommended as being broadly adapted, but rather is viewed as a niche wheat with unique attributes. Performance is best in southern Nebraska and similar growing areas in adjacent states. In these areas, Cougar can be grown wherever Thunderbird has been grown previously.
Millennium is a HRWW cultivar developed cooperatively by the Nebraska Agricultural Experiment Station and the USDA-ARS. Jointly released in 1999 by the developing institutions and South Dakota Agricultural Experiment Station, Millennium was selected from the cross 'Arapahoe/Abilene//NE86488'. The pedigree of NE8648 is Colt/3/Warrior 5*/Agent//Kavkaz. Millennium was released primarily for its superior adaptation to dryland wheat production systems in Nebraska (except southeastern Nebraska) and similar growing areas in South Dakota and adjacent states. However, additional years of testing with more severe winterkill are needed to identify its area of reliable production and adaptation in South Dakota. Millennium is an awned, white-glumed cultivar, with a field appearance most similar to that of Arapahoe.
Millennium was performance tested as NE94479 in Nebraska yield nurseries starting in 1995. In 2 years of testing in Nebraska cultivar performance trials, Millennium performed extremely well throughout most of the state, but it is best adapted to southwestern and western areas. The average dryland yield of Millennium (26 environments) was 4,200 kg/ha, which compares favorably to Alliance (4,150 kg/ha), Culver (4,190 kg/ha), and Niobrara (4,160 kg/ha). Millennium also performed quite well under irrigation (5,760 kg/ha), though would not be considered a high-management wheat because of its height as a taller semidwarf with good, but not exceptional straw strength under irrigation. The main advantages Millennium has compared to most other available wheat cultivars within its area of adaptation are its high grain yield, ability to yield well under favorable production conditions, and broad adaptation in dryland production systems.
Millennium is medium in maturity, with flowering about 0.5 days later than Arapahoe and 2 days later than Alliance. The mature plant height of Millennium ( 88 cm) is similar to that of Niobrara and 1 cm taller than that of Arapahoe. The coleoptile length of Millennium is moderately short, shorter than those of TAM 107 and Arapahoe. Millennium has good straw strength, similar to those of Ogallala and superior to that of Alliance, Arapahoe, Culver, Niobrara, and Pronghorn. The winter hardiness of Millennium is good to very good, similar to that of Abilene and comparable to that of other winter wheat cultivars adapted and commonly grown in Nebraska.
Millennium is moderately resistant to stem rust (most likely containing Sr6 and Sr24); leaf rust (most likely contains Lr24, Lr10, and possibly Lr16); and Hessian fly (similar to Arapahoe, and most likely contains the Marquillo-Kawvale genes for resistance), and susceptible to WSBMV and BYDV. In preliminary field tests, Millennium has exhibited a low level of tolerance to WSMV. Millennium has a good grain volume weight (76.5 kg/hl), which is higher than those of Arapahoe, Niobrara, and Culver, but lower than that of Pronghorn. The milling and baking properties of Millennium were determined for 5 years by the Nebraska Wheat Quality Laboratory. In these tests, Arapahoe and Scout 66 were used as check cultivars. The average wheat protein content of Millennium was lower than those of Arapahoe and Scout 66. The average flour extraction on the Buhler Laboratory Mill for the Millennium was similar to that of Scout 66 and higher than that of Arapahoe. The flour-ash content was similar to those of the check varieties., but the average flour protein content was lower. Dough-mixing properties of Millennium were lower than those of Arapahoe and stronger than those of Scout 66. Average baking absorption was slightly less than those of the check varieties. The average loaf volume of Millennium was similar to that of Arapahoe and larger than that of Scout 66. The scores for the internal crumb grain and texture were good, similar to those for Arapahoe, but less than those for Scout 66. The overall end-use quality characteristics for Millennium should be acceptable to the milling and baking industries.
Millennium should be well adapted to most dryland wheat production systems, with average or above-average yield potential in most of Nebraska except the southeastern district, and should perform well in similar growing areas in adjacent states.
Nuplains is the first HWWW developed by the USDA-ARS (C. J. Peterson, now with Oregon State University) and the Nebraska Agricultural Experiment Station. Nuplains is a high yielding semidwarf wheat adapted to dryland and irrigated production. Nuplains is well suited to higher-yielding dryland conditions and should be an excellent companion wheat for Trego, a dryland white wheat recently released by Kansas, which seems to be better adapted to more stressful and lower yielding conditions.
Two experimental lines (NE94654 and NE95473) are under large-scale
increase for possible release in 2000. NE94654 (Arapahoe/Abilene//Arapahoe)
is a semidwarf Arapahoe type with good winter hardiness; very
good dryland yield; and average straw strength, kernel weight,
and test weight. The coleoptile length is longer than that of
Arapahoe and, hence, would be considered long for a semidwarf
wheat. NE94654 is a white-chaffed, awned, HRWW that is medium
late in maturity (later than Arapahoe) and medium in plant height
(slightly shorter than Arapahoe). The best performance areas seem
to be west central and western Nebraska under dryland conditions
where its later maturity can be favored. The straw strength of
NE94654 precludes it from being grown under irrigation. NE94654
is moderately resistant to stem rust (most likely contains Sr6
and Sr24); leaf rust (most likely contains Lr16,
Lr24, and other unnamed genes); and Hessian fly (most likely
has the Marquillo-Kawvale genes for resistance) and is susceptible
to RWA, BYDV, WSBMV, and WSMV. NE94654 has very good to acceptable
end-use quality in our tests.
NE95473 (unknown Russian parent/Arapahoe) is a semidwarf
Arapahoe type with good winter hardiness, straw strength, and
test weight; very good dryland yield; and lower kernel weight.
A white-chaffed, awned, HRWW, NE95473 is medium in maturity and
medium in plant height (similar to Arapahoe for both traits).
The best performance areas seem to west central and western Nebraska
under dryland conditions. NE95473 has adequate straw strength
for irrigated production. NE95473 is moderately resistant to stem
rust (most likely contains Sr6 and Sr17), is heterogeneous
for Sr24) and Hessian fly (most likely has the Marquillo-Kawvale
genes for resistance); moderately susceptible to leaf rust (most
likely contains Lr10 and is heterogeneous for Lr24);
and susceptible to RWA, BYDV, WSBMV, and WSMV. NE95473 has acceptable
end-use quality in our tests.
S. Baenziger.
Two lines NE96T422 and NE96T441 are under large-scale increase for possible release as forage triticales. Of the two, NE96T422 is better adapted to Nebraska, and a commercial company may have an interest in NE96T441 for forage production outside Nebraska. A number of good grain types have been developed, and market development will need to be considered.
A. Mitra, T. Clemente, S. Sato, S. Baenziger, and M. Dickman.
Mr. Todd Campbell, a graduate student, is genetically characterizing 2-5A transgenic plants. Twenty-five independently transformed wheat plants were produced by microprojectile bombardment of 1,080 immature embryos with a three-plasmid system. Cotransformation is common (in this research, genes on three plasmids were inserted 36 % of the time). Two of nine transgenic families containing all three plasmids were characterized for the segregation of the two genes of interest in T1, T2, and T2 testcross generations using PCR. These data suggest that the two genes of interest are linked in both families studied. Based on the inheritance of the two genes of interest, one transgenic family would be desirable for use in a breeding program, because it contains tightly linked genes. The other family studied would not be desirable for use in a breeding program, because the two genes segregate aberrantly or a second copy of one of the genes may segregate in the background.
Our future plans include further genetic characterization of transgenic plants, developing optimized transgenes for expression in wheat and adding possible fungicidal genes as part of the U.S. Wheat and Barely Scab Initiative research (coöperative project among Drs. Mitra, Dickman, Clemente, and Baenziger). The four genes (which may affect scab disease development) we wish to insert into wheat encode a) CED9; b) IAP (inhibitor of apoptosis-programmed cell death); c) lactoferrin and a related derived protein, lactoferricin; and d) oxalyl-CoA-decarboxylase. With the exception of CED9, we have created over 10 events for the other genes.
M. Shah and P.S. Baenziger.
This research was undertaken with the expectation that as we learned more about the wheat genome, we would be able to develop better breeding strategies. Dr. Mohammed Maroof Shah, a former graduate student, completed the field evaluations and molecular-marker characterization of the recombinant inbred chromosome lines (RICLs) for CNN-WI DS3A. As in our previous studies, the CNN-WI DS3A line in Shah's studies also had significantly higher grain yield and kernel weight than CNN. The CNN-WI DS3A also was significantly earlier flowering with short stature than CNN. The QTLs for grain yield on chromosome 3A, despite having a significant 'G x E' interaction, have been identified in eight (Berke et al. 1992a); four (Yen et al., 1997); and now in seven environments (Shah et al. 1999, 2000). Dr. Shah identified and mapped a single-gene locus (Eps: earliness per se) controlling early flowering on chromosome 3A. The Eps locus showed significant pleiotropic or linkage effects on plant height and kernel weight. In addition, Dr. Shah identified and mapped QTLs for plant height and yield component traits (e.g., kernel weight, kernel number, and spike numbers) in individual environments, as well as over all the testing environments. The QTL(s) for yield per se were not identified in the combined environment analyses. However, yield QTLs were identified in several individual environmental trials. The marker-QTL association was found to be strong, and the amount of variation explained by the markers for a majority of the traits was higher than in previous studies on wheat for these traits. The QTLs controlling different traits appeared to be in two clusters on the chromosome. The fact that Dr. Shah was able to identify and report a very high level of polymorphism between wheat cultivars is important. Besides the identification and mapping of the Eps locus and other important gene clusters on chromosome 3A, the higher levels of polymorphism between cultivated wheats is the first report on this area will be utilized for high density mapping and tagging important genes. These investigations will further our understanding of the wheat genome and its utilization for improving this crop.
In a follow-up study using additional RICLs (a total of 98 RICLs) and additional replications, Mr. Todd Campbell with the help of Drs. Shah, Gill, Nettleton, and Eskridge, identified a QTL for grain yield per se on chromosome 3A. The QTL is very near to the Eps gene on that chromosome, and we are most interested in determining if the QTLs for grain yield and anthesis date are linked or pleiotropic. A putative second QTL for gain yield was identified further along the chromosome, but permutation statistics indicate it will need further confirmation. In the next year, we will concentrate on developing additional markers to fill the map gaps and to further confirm the identified QTLs for several important agronomic traits.
R. French and D. Stenger.
Development of an infectious cDNA clone of wheat streak mosaic virus. A full-length cDNA clone of WSMV was constructed in pUC18 with an upstream SP6 promoter. In vitro transcripts were generated in SacII-linearized plasmid DNA that then was used to inoculate wheat seedlings. More than 60 % of the plants inoculated with transcripts produced in the presence of the 7-methyl-guanosine cap analog developed mosaic symptoms typical of WSMV infection. The presence of virus in systemically infected leaves of inoculated plants was confirmed by RT-PCR of the WSMV P3 gene, and by serological detection of WSMV coat protein on immunoblots. Transcripts not containing a 5'-guanosine cap structure were not infectious. The plasmid DNA containing WSMV cDNA was prone to spontaneous rearrangement during prolonged culture in E. coli. A parallel cDNA clone in plasmid pACYC177 was more stable. This tool will be valuable to establish WSMV gene expression and function.
Identification of interactions among wheat streak mosaic viral proteins. The genome organization of mite-transmitted WSMV appears to parallel that of members of the Potyviridae with monopartite genomes, but there are substantial amino acid dissimilarities with other potyviral polyproteins. To initiate studies on the functions of WSMV-encoded proteins, a protein interaction map was generated using a yeast two-hybrid system. Because the pathway of proteolytic maturation of the WSMV polyprotein has not been determined experimentally, random libraries of WSMV cDNA were made both in DNA-binding domain and activation domain plasmid vectors and introduced into yeast. Sequence analysis of multiple interacting pairs revealed that interactions largely occurred between domains within two groups of proteins. The first involved interactions among NIa, NIb, and coat protein (CP), and the second involved HC-Pro and CI. The two-hybrid assay then was performed using full-length genes of CI, HC-Pro, P1, P3, and CP, but no heterologous interactions were detected. However, in vitro binding assay using GST fusion proteins and in vitro translation products revealed mutual interactions among CI, HC-Pro, P1, and P3. Further analysis of the interaction between HCPro and CI by deletion mapping suggests that the NH2- and COOH-terminal regions of CI independently interact with the COOH-terminal region of HC-Pro. The multiple homomeric and heteromeric molecular interactions suggest that various viral processes might be regulated via a network of viral protein complexes.
R. Graybosch.
An enzyme-linked immunosorbent assay for the identification of wheats carrying null alleles at genetic loci encoding the granule-bound starch synthase (Coöperative project with J. Skerritt, CSIRO, Australia). Granule-bound starch synthase (GBSS) is the enzyme responsible for the production of amylose within wheat endosperm cells. Hexaploid bread wheats contain three genetic loci that encode isoforms of GBSS. Null, or nonfunctional, alleles have been discovered at each locus. Wheat breeding lines with one or two null alleles produce starch with reduced amylose contents. Lines with three null alleles produce amylose-free or waxy starch. Antibodies raised against the granule-bound starch synthase were developed and used to produce a rapid assay capable of identifying wheat lines with two or more null alleles. The presence of two or more nulls was found to reduce GBSS content of purified starch grains. GBSS content of lines with only one null allele did not differ from that of wild-type (three active genes) wheats. The antibody system provides a quantitative method by which double-null lines can be identified readily in wheat breeding programs and in grain handling and milling operations.
Improved quality of 1RS wheats. Wheat lines with rye chromosome 1RS, generally in the form of T1AL·1RS or T1BL·1RS wheat/rye translocations, have become widespread in many of the world's wheat breeding populations. Chromosome arm 1RS confers to wheat distinct advantages, including resistance to a number of diseases and insect pests and improved yield and adaptation, at least in some environments. Chromosome arm 1RS also conditions diminished gluten strength, easily measured by diminished SDS-sedimentation volumes or decreased tolerance to dough overmixing. The loss of gluten strength in 1RS wheats is attributed to the decline in HMW-glutenin polymers brought about by the substitution of monomeric rye secalin proteins for polymer-forming wheat glutenin proteins. Two backcrossing schemes were designed to increase glutenin polymer and glutenin strength in 1RS wheats. Chromosome 1A-encoded HMW glutenins from the tetraploid wheat T. turgidum subsp. dicoccoides were backcrossed into T1AL·1RS and T1BL·1RS wheats. This procedure increased the number of genes encoding HMW glutenins from 5 to 6. However, no gain in gluten strength in the recipient 1RS wheats resulted. A more successful strategy was to backcross 1RS into N86L177, which has high-protein genes ultimately derived from Atlas 66 and high-protein, strong-gluten genes derived from Plainsman V. The 1RS lines produced via either two or four backcrosses to N86L177 displayed gluten strength nearly equal to that of non-1RS sister lines and markedly better than that of the 1RS donor cultivars. Derived 1RS lines also were equal in grain yield to the 1RS donor parent. Although the precise genes encoding the elevated gluten strength of N86L177 are unknown, use of this genetic background can successfully improve the quality of 1RS wheats.
Ms. Sharmilla Mitra joined the program to work on characterizing transgenic wheat lines. Mr. Hikmet Budak joined our program as a graduate student working under Dr. S. Baenziger. Mr. Kim Kyung-Moon completed his Ph.D. and returned to Korea where he is working for a biotechnology company. Dr. David Shelton departed to assume a leadership position with the Wheat Marketing Center, Portland, OR.