Slow Advances in Wheat Biotechnology

Crop and Soil Environmental News, April 1998

Charles Hagedorn
Extension Specialist, Biotechnology
Virginia Tech

Progress, although slow, is being made in genetic engineering to improve wheat by developing such characteristics as drought tolerance and diseases resistance. Most research on wheat is located in universities scattered across the Great Plains states and is directed towards first understanding the complexities of the wheat plant (a grass) with the goal of eventually using biotechnology to develop transgenic wheat with unique desirable traits.

One reason the work is progressing slowly is that wheat is a low-value crop compared to cotton, rice, and soybeans; and the issue, yet to be addressed, of whether a costly genetic approach to wheat can be justified or not. A second reason (and perhaps the most critical one), is that the genome of wheat (a genome is a set of chromosomes) is 10 to 20 times larger than crops like cotton or rice. Improving wheat by biotechnology will be a far more complex and time-consuming challenge because the wheat genome is so large. While biotech will not be a magic bullet for wheat, it can allow scientists to "fix" certain defects in the plant and possibly allow the insertion (into wheat) of exotic traits that were not there before.

Regardless, the private sector is interested in developing transgenic wheat. For example, Monsanto (the biotechnology company with transgenic cotton, soybeans, and corn already in the marketplace), acquired the breeding programs of two established wheat development firms back in 1982, one being Hybritech Seed International, a leader in hybrid wheat. According to a Monsanto spokesperson, wheat biotechnology is very important since wheat is a worldwide crop and there is a "fit" with biotechnology approaches in other crops. Monsanto has no transgenic wheat products on the commercial track yet.

Among universities, Kansas State, Cornell, Oklahoma State, and Texas A&M universities are working on wheat at the molecular biotechnology level. At Texas A&M, Allan Fritz (wheat breeding and genetics), is tagging and mapping DNA markers on the wheat chromosome to locate the genetic basis of traits that are of particular interest to Texas wheat growers. His program has identified DNA markers on the wheat chromosome for Russian wheat aphid (RWA) resistance and for greenbug resistance. This knowledge could eventually lead the way to RWA and greenbug resistant wheat varieties. His research is just starting to search for a genetic "mechanism" to influence wheat's susceptibility or tolerance to the nemesis of wheat farmers, leaf rust disease.

All plants (including wheat) can be changed genetically by using two basic approaches: 1) transformation, and 2) the use of known DNA markers. Transformation involves the introduction of genes into a plant from some outside foreign source, like a fungal pathogen. The pathogen can carry the trait into the parent plant. The use of DNA markers, on the other hand, allows a gene to be inserted into a plant using what is already known about the chromosomes of a plant through the mapping process. It also allows the "pyramiding" of one trait or another. One problem with either approach in wheat is that wheat carries many "highly repetitive" DNA markers that complicate the search and the ultimate biotech application. It has been only recently discovered that all plants originate from as few as three ancestors. While there is much that can be done with wheat, the wheat genome is so very large that advances in wheat biotechnology will not happen very fast. For example, there is an international group of scientists that has set a target of ten years to complete a genetic map for wheat, barley, and rye as part of what is called a plant genome project.

At present, the process of transformation in wheat has been carried out most successfully in spring wheat, notably the Bob White variety. Any engineered spring wheat would have to be back-crossed into winter wheat. Transformation of wheat is actually carried out either by a so-called gene gun or by the use of a bacterial vector (agrobacterium) in a dish in a laboratory. Wheat researchers agree that there appears to be a tremendous potential for wheat improvement, as biotechnology could be used to add herbicide resistance, drought tolerance, and disease resistance, including viral disease resistance. However, there will probably not be transgenic wheat varieties planted in farmerís fields for many years.

On the grazing side of wheat production, even longer-term research may produce a wheat that might grow back faster following grazing, or wheat with more overall forage vigor -- a biotechnology improvement for the forage component of wheat. But then there is the question of the value of a wheat crop and how planting seed would be handled from a patent protection standpoint. Most growers catch and replant their own seed today. This isn't allowed in a patented and licensed seed product, such as the Bt cotton varieties.

Oklahoma State University scientist Arron Guenzi, explains the transformation process this way: It's a matter of taking a gene from one species, isolating it and characterizing it (determine its genetic code) and then manipulating it so that a trait is expressed in a target -- a living plant. This is all done in a test tube in the laboratory. Guenzi is currently working with a known anti-fungal gene (glucanase) from alfalfa and one from rice (chitinase) that has the potential to help make wheat more leaf rust resistant. This could occur by making the plant's cells less prone to fungal attack. Guenzi also is working with a bacterium that may influence drought tolerance via its manufacture of a sugar alcohol, mannitol. The alcohol is known to protect cellular membranes under drought stress. Both university and private sector scientists are currently discussing the potential value of any kind of transgenic wheat -- and whether it could be a profitable venture for either universities and/or companies such as Monsanto (and several other biotech firms known to be looking into the potential of developing transgenic wheat).

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