Plant Molecular and Cellular Genetics Lab
Tuskegee University, Tuskegee, Alabama

Reported by C. S. Prakash

The primary goal of this lab is to utilize genetic engineering techniques to enable improvement of crop plants. Most of our work is focused on sweetpotato, the sixth largest crop in the world. Use of genetic engineering techniques is enabling scientists to improve the productivity of crop plants. Genetically engineered plants that are tolerant to diseases and pests are now a reality in few crops. The major research goals of our lab are to genetically engineer sweetpotato for improved productivity and to analyze the DNA variation in sweet potato and related species.

We grow sweet potato plants in tissue culture conditions and maintain nearly one hundred varieties in test tubes (Figure 1). We have introduced foreign genes into sweetpotato varieties. Using a device called `Gene Gun'that uses a 0.22 caliper bullet and DNA coated on microscopic tungsten particles, foreign genes are literally blasted into the cells of sweetpotato. Another technique uses a soil bacterium (which causes crown gall disease) as a vehicle to deliver foreign genes into the cells of sweetpotato. The genetically engineered bacteria infects the plant tissue and transfers genes into plant cells. We have developed several transgenic sweetpotato plantlets and have confirmed the presence of foreign genes in these plantlets by DNA analysis (refer to the gus-positive leaf (bottom) and the gus-positive root (left). We have developed a technique to produce somatic embryos from sweetpotato leaves which has helped us to produce transgenic plants. Transgenic plants are now being tested under greenhouse and hydroponic conditions. We have also introduced genes for disease resistance, herbicide tolerance and high quality protein into sweet potato.

Another research program in our lab concerns studies on DNA variation in sweetpotato and its related species. These studies have applications in breeding and selection, fingerprinting of varieties, and in understanding how the crop evolved. DNA is extracted from sweetpotato varieties, and pieces of DNA amplified using the polymerase chain reaction. DNA fragments separate based on size, and a `bar code'like pattern results that may differ among varieties of sweetpotato. These patterns have enabled scientists at Tuskegee University to positively identify sweetpotato varieties and also understand the evolution of sweetpotato.