Engineering turf for the future
For the past several decades, breeders have made dramatic improvements in turfgrass cultivars of many species. Cultivars available today offer greater attractiveness and durability than ever before. As a complement to classical breeding techniques,
Engineering turf for the future
For the past several decades, breeders have made dramatic improvements in turfgrass cultivars of many species. Cultivars available today offer greater attractiveness and durability than ever before. As a complement to classical breeding techniques, the techniques of genetic engineering have the potential to provide turfgrass breeders an additional tool in their efforts to develop the ideal grass. The Rutgers Turfgrass Biotechnology Program is actively working with the Rutgers Turfgrass Breeding Program to develop turfgrass cultivars with increased disease and herbicide resistance.
The term genetic engineering refers to manipulating the DNA, or genes, of an organism. Plant transformation refers to the process of introducing a gene from some other organism into a plant species. Scientists are discovering genes from organisms as diverse as viruses, bacteria, fungi and plants that can confer beneficial new characteristics to particular plant species. Plant-transformation technology thus offers the opportunity to introduce into a plant species genes from unrelated organisms. This would be impossible using traditional breeding methods.
Transformed crops such as corn, soybeans and cotton, developed through genetic engineering, already are commercially available. Genetic engineers transformed these crops with genes conferring insect and herbicide resistance to those plants. We are using similar techniques, in combination with breeding, for the development of improved turfgrass cultivars. Currently, this work is in the research stage, and no transformed turfgrass cultivars are yet commercially available. However, we do have transformed plants containing several potentially beneficial new genes. We are field-testing these plants to determine the effectiveness of the new genes.
In the Rutgers Turfgrass Biotechnology Program, we are particularly interested in transformation of creeping bentgrass. The high maintenance requirements of bentgrass make it a good candidate for improvements that will ease this maintenance burden. Herbicide resistance, disease resistance and increased drought tolerance are some of the traits we feel we can develop in bentgrasses using this technology. We also have recently started a program on the transformation of tall fescue.
Biotechnology at work Currently scientists employ several methods for plant transformation. For grasses, the most effective method is particle bombardment, or biolistic transformation. This method uses an apparatus we commonly call a gene gun. With this method, small particles of gold or tungsten are coated with the DNA of the new gene. The gene gun then "shoots" these particles at high velocity into the grass-plant cells. The plant cells that we bombard are clumps of unorganized cells called callus, growing in tissue culture. If we germinate grass seeds on a special medium containing high levels of plant hormones, the cells grow in an unorganized state and form callus tissue. In some of the bombarded callus cells, the new DNA dissociates from the metal particle and becomes integrated into the cell's own DNA. We don't yet understand how this occurs, but the result is that the plant cell now has a new gene, which originated from another organism. By manipulating the culture conditions of transformed callus cells, we often can stimulate them to regenerate a complete new plant. The new, transformed plant now has the new gene in all of its cells.
Herbicide resistance In the Rutgers program, Christina Hartman, Lisa Lee, Peter Day and Nilgun Tumer recently developed creeping bentgrass resistant to the herbicide bialaphos and the related molecule phosphinothricin (also known as glufosinate-ammonium, the active ingredient in the commercial herbicides Herbiace, Finale and Basta). The herbicide-resistance trait comes from a gene isolated from a bacterium, which works by producing an enzyme that inactivates the herbicide. Transformed plants containing this bacterial gene therefore are resistant to the herbicide.
Obviously, herbicide-resistant creeping bentgrass would be useful to golf-course superintendents. They could spray a green with a herbicide that kills the weeds, such as Poa annua, while leaving the creeping bentgrass unaffected. We field-tested the transformed creeping-bentgrass plants and found them to be resistant to bialaphos at one and three times the normal field rate. We are continuing our work with these plants and have produced herbicide-resistant progeny plants for eventual use in developing a new cultivar.
Disease resistance In addition to herbicide resistance, we also are interested in disease-resistance genes. Creeping bentgrass is susceptible to many fungal diseases and sometimes requires extensive use of fungicides for disease control. Because little natural disease resistance to some of the important bentgrass diseases exists, transformation with new genes for disease resistance is a promising strategy for cultivar improvement. Plants that are more resistant to fungal pathogens would require fewer fungicide applications for maintenance, with obvious benefits. Our research is being supported by the United States Golf Association, because they are interested in the development of cultivars that require less pesticide use.
We currently are working with several genes that have provided resistance to fungal pathogens in other plant species when transformed with those genes. The genes originated from a bacterium, two types of fungi and the pokeweed plant (Phytolacca americana). Thus, our program on turfgrass improvement has benefited greatly from the scientific discoveries of our colleagues.
The disease-resistance