July 22, 1997http://hordeum.msu.montana.edu/genome/
Priority Needs for Wheat and Barley Biotechnology
Wheat and Barley Improvement for the Next Century:1

Priority Needs for Biotechnological Approaches to Wheat and Barley Improvement

Summary

     The Triticeae crops (wheat, barley, rye, and triticale) are a foundation of human nutrition and of enormous economic importance both to the US and worldwide. Modern technological tools are now ready to transcend many of the current limitations on the genetic improvement of these crops. However, the US research system has not focused on the development of these technologies and their application to the Triticeae. This prospectus discusses some of the needed resources and suggests both immediate priority needs and a framework of resources required for application of biotechnology to improvement of wheat and barley to sustain and improve production capabilities for these important crops. A five-year program is projected to complete the objectives at an estimated total cost of 22 million dollars.

Introduction

Wheat is indisputably one of the critical agricultural crops in the US. In 1996, 76 million acres were planted in wheat along with another 8 million acres in barley, triticale and rye (compared to 79 million acres for corn). Wheat is a cornerstone of US agricultural exports with an estimated value of 6.8 billion dollars in fiscal 1996. Barley alone, with farmgate value of over 900 million dollars annually, is a key commodity in products valuing more than 181 billion dollars.

     The importance of wheat internationally is evident from the 1996-97 worldwide production estimates of 579 million metric tons (compared to 573, 558, and 132 million metric tons worldwide for corn, rice, and soybeans, respectively). In addition to its basic caloric value, wheat, with its high protein content, is the single most important source of plant protein in the human diet. Wheat is a member of the Triticeae group of cereals, which includes barley, rye, and triticale. These cereals are genetically so similar as to be considered, for many purposes, a single genetic system. When the 1996-97 world production forecasts of 154 million metric tons of barley are added to the production of wheat and the smaller amounts for rye and triticale, the importance to humanity of the Triticeae system is evident.

     Wheat and barley breeding programs in the US have made steady improvements in productivity while maintaining grain quality and adequate resistance to numerous disease and insect pests. This progress, which began nearly a century ago, has been the result of basic research that made available unexpected and valuable genetic variation, and which introduced breeding strategies and screening technologies that changed the scope and efficiency of wheat and barley breeding. There is evidence that this rate of progress is beginning to wane with traditional plant breeding techniques and resistance to certain pests has been difficult to attain. Now, the newer molecular genetic technologies offer the promise to sustain gains in plant breeding programs of the 21st century.

     Among the recent accomplishments of biotechnology applied to the Triticeae is the completion of molecular genetic framework maps of all the wheat and barley chromosomes2. In addition, the demonstration of the genetic transformation of wheat, barley, and rye establishes that direct gene manipulation in crop improvement is possible. Such developing technologies are poised to have a major impact in the practical improvement of wheat and barley varieties and offer great promise for the future.

     The application of these technologies can require significant resources in the development stages. Fortunately, it may not be necessary to repeat all developments for every crop. The exciting finding that the genomes of all the cereals share extensive genetic similarity means that scientific advances in other cereals, such as rice and corn, can often be utilized by wheat and barley researchers. While this similarity in the genetics of the cereals has tactical advantages in research, there are some technology developments which are specifically required for wheat and barley. There are currently a number of ongoing discussions and plans for various plant genome programs. We agree that a broadly planned and executed "Crop Plant Genome Program" is a logical format to advance all aspects of US crop development. We support a unified plant approach and a possible "grass" genome unified program, as long as the specific needs of wheat and barley are addressed.

     US wheat and barley breeding laboratories, public and private, across the US are poised to develop and use technologies such as microsatellite markers, large insert DNA libraries, expressed sequence tags (EST), and transformation. It is important that the development of these scientific resources be adequately funded and focused to allow the US to establish and maintain a leading role in the application of biotechnology to crop improvement and to utilize these technologies in programs with real practical impact on wheat and barley productivity and quality at the farm level.

     A stumbling block to the development and application of such technologies to wheat and barley improvement is the inadequate focus of sufficient resources. To this end we are endeavoring to inform all sectors of the wheat and barley communities of the critical technology needs, and encourage discussions on how these needs can be met for the advance of cereal technology into the coming century.

A Wheat and Barley Genome Initiative

The above considerations have stimulated the concept of a unified approach for wheat and barley for developing molecular tools and their applications in basic research and plant breeding. Due to the rather close genetic relationship between wheat and barley, progress in locating and manipulating genetic determinants of economically important phenotypes in one crop can immediately be transferred to the other crops. Examples of opportunities and production constraints in wheat and barley improvement are: unique quality profiles for domestic and export markets, genetic resistance to biotic and abiotic stresses, and input use efficiency.

Critical Molecular Resources

The set of molecular resources and tools identified below are critical to the implementation of biotechnological approaches to wheat and barley improvement. These methods permit discovery, identification, isolation, and transfer of genes from practically any source to important wheat and barley varieties. In particular, these methods facilitate the rapid transfer of genes from one wheat or barley variety to another, and are especially useful for exploiting genes, such as disease and pest resistance, from wild species to cultivated wheat and barley.

Advanced DNA Marker Technology

     Microsatellite DNA Markers: Microsatellites are a new class of DNA marker used extensively in human genetics and human genetic diagnostics and the leading type of marker technology in virtually all animal species research. The major advantages of microsatellites are their ease of use, low cost of analysis, and ability to detect genetic differences even among closely related individuals. The first two advantages are critical for the widespread use of DNA markers in large scale breeding programs. The third characteristic is of paramount importance in modern plant breeding programs in which crosses are often made between elite parental lines that are genetically quite similar. Thus, microsatellite DNA markers offer the promise of DNA "Marker-Assisted Selection" that can function in "real world" wheat and barley breeding programs for the development and release of high yielding varieties. The disadvantage is the inability of the current research system to focus support for such high unit cost developments.

     Alternative Marker Strategies: Although microsatellites are considered the most useful type of markers for development, other technologies are also ready for use. An example is AFLP (Amplified Fragment Length Polymorphism) markers. Such newer methodologies may offer additional advantages and options but need further development.

Large Insert DNA Libraries

     A fundamental requirement for isolating specific agronomically important Triticeae genes and to understand genetic mechanisms of the Triticeae is the availability of DNA clone libraries containing large fragments of the Triticeae genomes. One technology to accomplish this is to introduce genes of Triticeae into bacterial chromosomes to create 'bacterial artificial chromosomes' (BACs). This technology provides the opportunity to isolate a targeted gene from a cereal genome. Gene isolation then provides a potential for a gene transfer and to design new variants of the gene that wheat and barley breeders can incorporate into breeding programs to improve disease resistance, grain quality, drought tolerance, and other agronomic characteristics.

Expressed Sequence Tags (ESTs)

     A major portion of the Human Genome Project has focused on the isolation, DNA sequence determination, and analysis of expressed DNA sequence tags. ESTs are the products of genes which serve as the templates for the synthesis of proteins and ultimately determine the shape, size, and characteristics of an organism. ESTs make it possible to determine a putative function of a cereal gene by computer comparison of its EST with the EST bank which includes virtually all organisms currently investigated by geneticists, including humans. This capability would greatly assist wheat and barley geneticists in the identification and isolation of economically important genes.

Transformation Technology

     Gene transformation is the process of introducing genes into plants by methods which by-pass the sexual seed production process. Transformation technology has been demonstrated in wheat and barley. New and valuable genes can be introduced into cereals via transformation that are not available through traditional breeding practices. However, a number of impediments exist to the widespread use of this technology. The procedure is still too inefficient, requires too much expertise for routine use, and is limited to only a few varieties or types of wheat and barley. In addition, our general knowledge of transgenic gene expression is insufficient. As a result, most elite breeding lines cannot be used for gene transformation. Improvements in the technology are needed to provide efficient and useful wheat and barley transformation which can be easily employed in applied breeding programs.

Molecular Breeding: Applications to Wheat and Barley Improvement

The development of molecular tools is necessary to identify genes for transfer to varieties, to tag or mark them as aids to selection, and for gene transformation. These tools and methods support the enhance traditional breeding approaches and are applicable to the transfer of any trait, qualitative and quantitative, for rapid and efficient development of input-use efficient varieties with unique quality profiles. The public sector continues to play a key role in wheat and barley variety development. Without unique and better varieties, US cereal producers will not be competitive. To use molecular tools effectively, breeding programs will require advances in automated genotyping, data management, and biocomputing. Such services could be provided by regional genetic diagnostic centers, similar to the already existing wheat and barley quality evaluation laboratories. Thus breeders would have access to the most up-to-date technologies and would not require their own laboratories for routine operations, such as gene tagging. For example, Fusarium head blight is a serious disease of both barley and wheat over a wide geographic area. Genetic resistance is the key to long-term cost-effective production. Molecular tools may be used to discover and genetic variation for resistance in some of the species of the Triticeae, such as wild grasses. Novel genes and gene regulation for disease management can be addressed for both crops. Likewise, genetic manipulations can be used to enhance seed protein, carbohydrate and enzyme properties to capitalize on new domestic and international market opportunities for both crops.

Objectives

The following are specific priority needs for resource development of the Triticeae crops if geneticists and breeders of these crops are to participate fully in the ongoing biotechnological revolution. Although development of many areas will be needed to assure maximum advancement of wheat and barley science, four have been identified as top priority and another group are given as secondary priorities, but a five-year time-frame is projected to meet all of these objectives. Costs are roughly estimated to be $4.5 million for the top priority items and $17.5 million for the second group, or a total of $22 million over the five years projected for this initiative.

Top Priority:

Second Priority

Organizational Aspects

There are already sufficient laboratories available throughout the US to carry out this work. Research would be done on the basis of proposals directed to the specific objectives of the Initiative. The proposals would be peer-reviewed and funds awarded on the basis of merit and record of previous accomplishments. The considerable experience in organizing and financing for the NABMGP and the US investigators of ITMI over the past five or more years has shown that coordinated programs can be developed, implemented, and completed. This Wheat/Barley Genome Inititiative could be managed from a contracted management office, through a private organization, a university, a government agency, or an NSF- or NIH-type organization. Central coordination is needed for preparation and review of proposals, allocation and transfer of funds, organization of meetings, electronic communications, and publication of results.

1  This prospectus was prepared by the US scientists participating in the International Triticeae Mapping Initiative (ITMI) and the North American Barley Genome Mapping Project (NABGMP). April 8, 1997. Further information can be provided by the ITMI Management Office, Genetic Resources Conservation Program, Division of Agriculture and Natural Resources, University of California, Davis, CA 95616. Tel. 916-754-8501, Fax 916-754-8505, itmi@ucdavis.edu and NABGMP from Patrick Hayes, Department of Crop and Soil Sciences, Oregon State University, Corvallis, OR97331, Tel.541-737-5878, Fax 541-737-1589, hayesp@css.orst.edu

2  Progress in Genome Mapping of Wheat and Related Species. Proc. 5th and 6th Public Workshops of the International Triticeae Mapping Initiative September 1995, Norwich, England and August 1996, Sydney, Australia. Report No. 18. Genetic Resources Conservation Program, Division of Agriculture and Natural Resources, University of California, Davis, CA 95616. 195 pages. April 1997.