OKLAHOMA
OKLAHOMA STATE UNIVERSITY
Department of Plant and Soil Sciences, 368 Ag Hall, Stillwater, OK 74078-6028, USA.
J.T. Edwards, B.F. Carver, and A.R. Klatt.
Jeff T. Edwards.
Wheat management research at Oklahoma State University continues to focus on the dual-purpose wheat production system (wheat that is both grazed and harvested for grain), which occupies the majority of seeded acreage in Oklahoma. This effort is balanced among three major objectives. The first of these objectives is to identify the physiological parameters that have the greatest impact of fall forage production and recovery from grazing. Factors currently being evaluated include leaf expansion rate, cardinal temperatures, and radiation use efficiency. We plan to use these data to develop a mechanistic understanding of wheat forage production and to establish critical traits to be selected for when breeding for a dual-purpose wheat-production system.
Our second objective is compare management strategies aimed at increasing fall forage production. To meet this objective we are comparing the economic returns of increasing fall wheat forage through variety selection, seeding rate, planting date, or nitrogen rate. From these data we plan to improve our research-driven recommendations to farmers.
Finally, we are coordinating validation/demonstration efforts for sensor-based nitrogen recommendations developed by researchers at Oklahoma State University. Through this work we plan to provide data necessary to fine tune the nitrogen-recommendation algorithm and increase adoption of sensor-based technologies throughout the southern Great Plains.
Brett F. Carver.
The Oklahoma Agricultural Experiment Station and USDA-ARS will jointly announce in May 2005 the release of Okfield HRW wheat and Guymon HW wheat. Okfield is a Clearfield™ wheat with the pedigree 'TXGH12588-120*4/FS4//2174'. The germ plasm indicated by FS4 originated with BASF Corporation (formerly American Cyanmid) and provides tolerance to the imidazolinone class of herbicides. Okfield is a more widely adapted cultivar than current Clearfield cultivars, with exception of areas challenged by WSBMV. Okfield shows exceptional recovery from early-planted grazing systems common in the southern Great Plains. Forage accumulation in the early autumn is average, whereas forage regrowth during the grazing period and recovery from grazing are above-average. We do not recommend extremely early seeding of OK02909C, because of its heat-sensitive germination response. Additional attributes compared with Above or AP502CL are slightly better tolerance to leaf rust, as evidenced by extended green-leaf retention and later first-hollow-stem stage (i.e., greater dormancy retention) by several days. Okfield also carries the potential to move into more drought-prone environments in the panhandle where 2174 has experienced some difficulty. Milling and baking characteristics are satisfactory, with above-average kernel size, below-average test weight, intermediate dough strength, and mean wheat protein content of 12.8 %.
One of the hurdles to expansion of the hard white wheat acreage in Oklahoma has been the lack of genetic diversity from which producers can choose to satisfy their specific management needs. Further growth of the HWW industry requires aggressive infusion of new cultivars to motivate producers to adopt HWW cultivars as an addition to, or even a displacement of, the HRW cultivars they currently grow. Guymon marks a new generation of HWW cultivars expected to emerge from the OSU Wheat Improvement Program. Guymon resulted from the cross, Intrada/Platte, and exceeds the grain yield of Intrada by up to 20 % at similar test weight. Guymon is positioned strictly for the southern High Plains and the panhandle of Oklahoma. Juvenile plant characteristics are befitting for a dual-purpose management system. Autumn forage accumulation up to cattle turnout should approximate, but likely not exceed, that of Intrada; forage regrowth will provide ample winter grazing without breaching winter dormancy. Guymon delivers a relatively high level of wheat protein, which exceeds 14.5 % in the targeted area. Desirable features of bread baking performance, including water absorption and loaf volume, justify its adoption in commercial, large-scale baking operations, but preliminary evaluation of alkaline noodle performance indicates color stability between Intrada (poor) and Platte (good).
A critical feature of this breeding program is what we have coined the GRAZEnGRAIN breeding system, instituted in 1997, which now generates all breeder lines for replicated yield trials. This breeding system interweaves two components throughout the 10-year cultivar development cycle: 1) multi-environment selection procedures common to any wheat-breeding program and 2) management system-targeted selection both within and between breeding populations. The result is a collection of breeding lines with potentially broader adaptation than selection in the absence of a management system component. This breadth of adaptation is what wheat producers need in the southern Great Plains if they continue to use cultivars indiscriminately in grain-only and early-planted forage-based production systems. Specific components of dual-purpose adaptation that are targeted include: temperature-insensitive germination, coleoptile elongation, early vigor, semierect to semi-prostrate growth habit, rapid leaf expansion, winter dormancy retention, and timely first-hollow-stem development, autumn and winter tillering capacity, and rapid recovery after grazing.
From a broader perspective, selection decisions involve six
trait complexes: 1) adaptation (traits governing fitness and
yield), 2) disease resistance, 3) insect resistance, 4) stress
tolerance, 5) grain quality (physical attributes), and 6) functionality.
Specific traits are identified for each complex on our website,
www.wit.okstate.edu, and will not be expanded here. We focus
selection on durable forms of leaf and stripe rust, including
the minor genes of resistance currently being introgressed by
A.R. Klatt, as well as BYD tolerance, resistance to the WSBMV/WSSMV
complex, and for only the second consecutive year, resistance
to powdery mildew. We also intend to continue emphasis on stay-green
expression, which provide a comprehensive index for foliar disease
tolerance. The traditional suite of quality targets center on
test weight, kernel size, protein content, absorption, and dough
strength; however, with the emergence in 2005 of the first advanced
line trial with strictly hard white wheat, selection efforts will
be redirected toward dual-purpose bread and noodle quality.
Arthur R. Klatt.
Adapted winter wheat cultivars with stable, long-term leaf rust resistance have not been identified for the southern and central Great Plains. A new cultivar typically maintains leaf rust resistance for a short period of time (2-4 years). In recent years, stripe or yellow rust also has caused significant production losses, and advanced lines in many programs lack good resistance. As a result, a primary objective of the germ plasm-development program at Oklahoma State University is to transfer minor gene resistance for leaf rust and stripe rust from CIMMYT spring wheat germ plasm into adapted winter wheat cultivars. This resistance is characterized by low levels of infection and is based on several minor genes (normally 3-5). Additionally, an extensive crossing program to the synthetic and synthetic wheat derivatives developed by CIMMYT is underway. This effort has multiple objectives, including potentially new genes for leaf and yellow rust resistance, improved kernel size, enhanced stay-green characteristics, drought and heat tolerance, and improved biomass and yield potential. The most advanced materials from this program will be evaluated as F5s in the current crop cycle.
Recent research results with irrigated spring wheat indicate
that spectral reflectance at selected wavelengths may serve as
an effective indirect selection tool for grain yield and biomass
production. Research is underway in Oklahoma to verify this relationship
in winter wheat. For information regarding this program, contact
Dr. Art Klatt, Department of Plant and Soil Sciences, 274 Ag Hall,
Stillwater, OK 74078 or via EMAIL at aklatt@mail.pss.okstate.edu.