ITEMS FROM THE UNITED STATES

 

OKLAHOMA


OKLAHOMA STATE UNIVERSITY
Department of Plant and Soil Sciences, 368 Ag Hall, Stillwater, OK 74078-6028, USA.

 

B.F. Carver, A.K. Klatt, and A.C. Guenzi.

 

Cultivar development and breeding research. [p. 258-259]

Brett F. Carver.

We continue to follow a modified bulk-pedigree selection method, whereby early generation (F2-F4) populations are selected and advanced as bulk populations, lines are derived from F4 populations as head rows, and subsequent generations are advanced primarily through line-selfing. Critical to this program is what we have coined the GRAZEnGRAIN breeding system, instituted in 1997, which now generates all of the breeder lines for statewide replicated yield trials. This breeding system interweaves two components throughout the 10-year variety development cycle: 1) multi-environment selection procedures common to any wheat-breeding program and 2) management system-targeted selection (dual-purpose and grain-only systems). The second component expands the scope of environments to which our materials are subjected and the portfolio of traits by which our materials are selected. 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 needed by wheat producers in the southern Great Plains if they continue to use cultivars nondiscriminately in grain-only and early-planted, forage-based, production systems.

Feeding the OSU breeding pipeline is a crossing program that features a 1:2 ratio of single (adapted/ adapted) and three-way crosses (typically adapted/non-adapted//adapted). Additional crosses enter the pipeline midstream from Bob Hunger, Department of Entomology and Plant Pathology, and Art Klatt, Department of Plant and Soil Sciences, whose report follows this one. Depending on the generation of breeding and the environment, selection decisions revolve on a ring of six trait complexes: 1) adaptation, 2) disease resistance, 3) insect resistance, 4) stress tolerance, 5) grain quality, and 6) functionality. Specific target traits are identified for each complex on our website, www.wit.okstate.edu. Traits that form the bulls-eye of all agronomic targets are resistance to leaf rust, stripe rust, and WSBMV, tolerance to low-pH soils, and reduced yield loss after autumn and winter grazing, whereas those constituting the bulls-eye of all quality targets include test weight, kernel size, protein content, and dough strength.

The Oklahoma Agricultural Experiment Station and USDA-ARS will jointly announce in May 2004 the release of Endurance and Deliver HRWW. Endurance originated in the wheat breeding program of Pioneer Hi-Bred International, Inc., and was tested under the experimental name, OK94P549-11 (pedigree: HBY756A/Siouxland//2180). Of the approximately 12 cultivars expected to occupy the most wheat acreage in Oklahoma in the next 5 years, eight are considered so early in first-hollow-stem (FHS) development to present adverse risk in grain production under the most predominant management system used in the southern Great Plains. Yield protection in a dual-purpose system may require various system-specific adaptations, but one that appears highly consequential is the capacity to remain vegetative throughout the winter grazing season. Endurance maintains a vegetative growth habit longer than most cultivars without delay in heading date. With this cultivar, the winter grazing season may be extended by as much as 2 weeks beyond early-FHS cultivars, with only minimal yield loss in the dual-purpose system (3%) compared to a grain-only system. Other favorable attributes are adult-plant resistance to wheat leaf rust races currently present in Oklahoma, moderate adult-plant resistance to wheat stem rust, and an intermediate to resistant reaction to wheat stripe rust. It also renders protection against highly acidic soils present in Oklahoma. Kernel size attributes, flour extraction, and flour ash content place Endurance in a desirable category for milling quality.

Deliver was tested under the experimental name, OK98690, and originates from the cross 'OK91724 (=Yantar/2*Chisholm)/Karl'. Because Deliver, an awnletted wheat, will be recommended for a dual-purpose system, a grain-only system, or a hay-production system, this tri-purpose wheat will provide producers flex-management options they currently lack with awned grain-type cultivars or awnletted forage-type cultivars. Flexibility derives from the ability to make in-season decisions on using a standing crop for grain production or for hay or late-season grazing. Deliver possesses moderate to substantial improvement in grain yield potential over currently grown cultivars and recently released cultivars yet to gain significant acreage, outstanding test weight patterns combined with unusually large kernel size, consistently high forage availability throughout the winter grazing season combined with a relatively late FHS date, broad-spectrum adult-plant resistance to the major foliar diseases in Oklahoma (leaf rust, stripe rust, WSBMV, and Septoria), and above-average milling and baking quality. Weaknesses include moderate susceptibility to lodging and to acid soils. Deliver consistently ranked as one of our best breeding lines from 2000 to 2003 for kernel weight (1,000-kernel weight = 31.5 g) and kernel size (kernel diameter = 2.36 mm and large kernel fraction = 76 %). That these attributes were recorded on an awnletted wheat in Oklahoma makes them even more unusual.

 

Variability enhancement/germ plasm development. [p. 259]

Arthur K. Klatt.

A major breeding effort is ongoing at OSU to incorporate new genetic diversity into the winter wheat improvement program. This variability enhancement program makes extensive use of spring wheat materials from CIMMYT and advanced lines from winter wheat-breeding programs in the region as the primary sources of genetic diversity. All introductions are screened for multiple disease resistance and agronomic type in Oklahoma and at a special coöperative disease nursery in south Texas, and the best materials are incorporated into the crossing program. The fifth cycle of crossing is currently in progress.

Winter wheat cultivars with stable, long-term leaf rust resistance have not been identified for the southern and central Great Plains. A new variety typically maintains leaf rust resistance for a short period of time (2-4 years). In recent years, stripe or yellow rust has caused significant production losses, and advanced lines in many programs lack good resistance. As a result, the breeding programs in the region must devote extensive resources to incorporate new genes for leaf rust resistance and to the development of adapted materials with good yellow rust resistance. A primary objective of the variability enhancement/germplasm development program at OSU is to transfer durable leaf rust and durable yellow rust resistance from CIMMYT spring wheat germ plasm into adapted winter wheat cultivars. Durable or slow rusting resistance is characterized by low levels of infection and is generally based on one or more major genes plus several minor genes. Additionally, an extensive crossing program to synthetics and synthetic 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, and improved biomass and yield potential. For information regarding this program, contact Dr. Art Klatt, Dept. of Plant and Soil Sciences, 274 Ag Hall, Stillwater, OK 74078 or via EMAIL at aklatt@mail.pss.okstate.edu.

 

Differential gene expression in wheat roots in response to infection by soilborne pathogens. [p. 259-260]

Arron C. Guenzi.

Coöperating in this project are Tim D. Samuels, J. Larry Green, G. Charmaine Naidoo, Larry Singleton, and Trish Ayoubi1 from Oklahoma State University, and John P. Fellers with USDA-ARS, Manhattan, KS, and Robert A. Gonzales with Samuel Roberts Noble Foundation, Ardmore, OK.

A systematic characterization is ongoing to define transcription profiles between the interactions of wheat roots of the cultivar Jagger and 1) G. graminis, 2) Rh. solani, and 3) P. arrhenomanes. These three species represent a complex of soilborne pathogens (i.e., the root-rots) that are endemic to all wheat producing regions in the Great Plains and much of the world. The severity of infection, and subsequent yield loss, can vary greatly between years and even within a given field. These diseases represent a largely under-researched class of diseases because of the difficulty in studying roots. As a result of this out-of-sight/out-of-mind phenomenon, the chronic loss due to these soilborne pathogens is probably grossly underestimated. Loss due to root-rots is also increased with the early planting associated with production of dual-purpose wheat. The most dramatic illustration of the chronic stress due to soilborne fungi is the dramatic increase in wheat yields; nearly two fold, associated with sterilizing soil in replicated field plots with methyl bromide.

A cDNA microarray representing genes differentially expressed during early stages of infection was created and used to characterize host transcription profiles during root surface colonization, epidermis penetration, and cortex colonization. The array consists of 4,200 elements that were replicated three times. One hundred and fifty genes were differentially expressed during the wheat G. graminis interaction. One hundred and five genes were differentially expressed during the infection by P. arrhenomanes into wheat roots. Surprisingly, there was little overlap between the gene expression profiles for these two pathogens with the same host genotype. These results provide targets for future functional analyses to dissect the biology of these diseases.

 

Publications. [p. 260]