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Submitted to: Annual Beet Sugar Development Foundation Research Report
Publication Type: Other Publication Acceptance Date: 7/3/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Disease and pest problems are responsible for decreases in production of sugar from sugarbeet. To combat these problems, genetic engineering approaches were investigated to enhance resistance to diseases and pests in sugarbeet. This progress report summarizes work in which genes from other living organisms increased disease and pest resistance when transferred to plants. Progress was made in the development of improved technology for transfer of genes to sugarbeet and in the modification of candidate beneficial genes for their eventual transfer to sugarbeet. The progress described in this report will be of benefit to scientists and commercial companies interested in the improvement of sugarbeet for resistance to pests and diseases. Technical Abstract: Cytokinins have been shown to alter phloem unloading as well as sink initiation, strength and capacity. A broad mobilizing effect of cytokinins has been demonstrated using cytokinin applications to organs or tissues that caused an increased photosynthate transport to the site of cytokinin application. To study the effects of cytokinin on various aspects of growth and sugar accumulation, sugarbeet cells were transformed with the isopentenyl transferase gene (ipt) (Snyder et al. 1999) that catalyzes the rate-limiting step of the cytokinin biosynthetic pathway. A number of morphological alterations commonly observed in ipt transformants were noted. Leaf and taproot cytokinin levels were elevated but leaf sucrose concentrations were comparable to those of the untransformed controls. Normal growth and development of the transgenic taproots was inhibited and resulted in decreased accumulation of sucrose. We are also developing biotechnological approaches to target the root maggot, a major sugar beet pest. By inhibiting the digestive enzymes in the maggot's stomach, the larva would in essence starve to death. Specific genes that produce potent inhibitors effective against digestive enzymes have been found to occur naturally in a number of plant species. Incorporation of some of the inhibitor genes isolated from one plant into another plant has been shown to be effective for insect control. It is necessary to determine the digestive enzymes of each individual pest to devise a rational control strategy. Analysis of excised stomachs from feeding root maggots revealed two major classes of digestive enzymes as targets for control. |
