Wheat Improvement through Genetic Engineering

Introduction

Trait improvements such as disease resistance and higher yields have been the goals of Kansas’s wheat breeders for decades. The introduction of new varieties with increased yield and enhanced resistance to pathogens (e.g. Jagger , 2137, 2145, and Overly), and the adaptation of hard white winter varieties (Betty, Heyne, Lakin and Trego) to western Kansas are just a few of the success stories. Even though significant progress has been made in the improvement of wheat, many more improvements are still possible. Persistence of pathogens such as Wheat Streak Mosaic Virus, leaf rust, and tan spot as well as emergence of new pathogens such as Karnal Bunt still pose a threat to the wheat crop. Conventional breeding programs will still play a major role in the development of new varieties with some of these traits. However, as with other crop plants, biotechnology and genetic engineering will become invaluable tools for our breeders.

Genetic engineering has the advantage of introducing discrete genetic information into a specific variety. Single or multiple traits can be incorporated into the wheat genome and expression of these traits can be regulated (both at a specific growth stage and at specific locations within the wheat plant including subcellular targets). If multiple traits are to be introduced, they can be placed all within in a single chromosomal location to facilitate breeding. As our general knowledge of biotechnology broadens, more traits will become available and more possibilities for wheat improvement will arise.

Current wheat trading partners are pressuring the US not to release GM-wheat. Although the issues need to be addressed and it is unlikely that transgenic wheat will be released in the next two to three years, conditions will change allowing broad acceptance of GM wheat. It is important to proceed with transgenic research so that products that we are working on today can be deployed in the field in a timely manner after the GM wheat issue has been resolved.

This proposal is a continuation our research currently funded by the KWC. The main objectives of our revised proposal are to 1) evaluate transgenic lines using gene silencing as a method of controlling Wheat Streak Mosaic Virus; 2) enhance our existing abilities to make transgenic wheat especially to direct gene expression to specific areas within the plant and reducing copy numbers of the transgene; 3) transfer traits to elite varieties through breeding; and 4) provide technical resources for KSU wheat research community.

Rationale and Significance

Wheat improvement through genetic engineering has been identified as a priority program for KSU’s Department of Plant Pathology, the Plant Biotech Center and K-State Research and Extension. The work outlined in this proposal falls under this umbrella. In addition this proposal also is within the scope of the KWC RFP interest areas. The proposed research will use biotechnology to enhance yield and adaptability traits (i.e. increase pest resistance). By simultaneously working on several traits we can improve the efficiency of our research efforts. Wheat transformation will occur year-round with little interruption. Our previous work has demonstrated that this approach works well to produce transgenic wheat plants.

Wheat Streak Mosaic Virus is one of the most important viral diseases to affect wheat. Low levels of resistance are available in cultivated wheat lines, but still suffer significant yield losses under field conditions (Siefers and Martin, 1988). A translocated short arm of Thinopyum intermedium is present in the germplasm KS96HW10-3. The resistance is good (Siefers et al., 1995) and the loci is tightly linked to the wsm1 gene (Talbert et al., 1996). This resistance is also found in KS93WGRC27 but does have some temperature sensitivity, but effective in preventing yield losses.

Wheat genetic engineering is not a trivial process; both expertise and a well-equipped facility are required to successfully undertake this endeavor. The Plant Transformation Facility at KSU is a well-established laboratory with a successful track record of producing transgenic wheat. By providing transformation services to the wheat community, it reduces cost and eliminates duplications. It also strengthens collaborative ties and allows investigators the opportunity to gather much needed preliminary data to become competitive for national grant dollars. This is a direct, tangible benefit supported by the Wheat Commission funding and in essence generating more data with lower input cost.

Last, genetic engineering of wheat has been looked on unfavorably recently by a small but vocal minority of the population. This public attitude is due, in part, to consumers who have not perceived any benefits thus far from other transgenic crops such as corn and soybean. Aside from the research, our lab grants tours to promote our research and biotechnology which helps gain consumer acceptance for biotechnology. Approximately 250-300 people visit the plant transformation laboratory annually). Visitors include high school students, producers, extension agents, commodity groups, foreign visitors, as well as university, legislative, and other governmental officials.

Procedures/Methodology

Our overall objective is to improve wheat through the use of biotechnology. The methodology of genetic engineering of wheat for both Objectives #1 and #2 will be similar as in the past (Chen et al., 1999; Anand et al., 2003a,b).

Duration of Project 3 years

Progress Report
A. Evaluate transgenic lines using gene silencing as a method of controlling WSMV

For the gene silencing experiments of Wheat Streak Mosaic Virus (WSMV) we in the process of engineering wheat cultures with a construct to silence viral coat protein gene expression. Five separate transformation experiments were conducted this quarter and are in various stages of the selection and regeneration process. Putative transgenic shoots are starting to be found in the experiments initiated in early November. We have also been selecting sequences within cylindrical inclusion (CI) protein, the RNA replicating protein and the helper component protein genes for constructing additional silencing plasmids. Of these three the CI protein plasmid has been completed.

In addition to the WSMV CP we are also engineering wheat cultures with the coat protein of Triticum Mosaic Virus (TriMV). Four separate transformation experiments were conducted this quarter and are in various stages of the selection and regeneration process. The majority of these experiments are still in the callus selection stage.

B. Refinement of tools for wheat genetic engineering.

No new progress to report for this objective this quarter.

C. Transfer genes to elite lines.

Line evaluations continue as reported last quarter. We are using different cultivars for transformation and tissue culture. These include: Jaggar, Ben, Maier, Lalbahadur, Lr34, and Lalbahadur.

D. Provide genetic engineering services to KSU wheat researchers.

We have continued to assist four separate laboratories with their wheat engineering needs. One lab is evaluating genes which may provide Fusarium Head Blight resistance, one lab is evaluating rust resistance candidate genes, one is screening genes for biofuel applications and one lab is evaluating a gene with green bug resistance. In total we are in the process of engineering wheat with approximately 20 separate genes. These projects are in various stages of the engineering process.