Submitted to: Southern Pasture and Forage Crop Improvement Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/27/1998
Publication Date: N/A
Technical Abstract: Alfalfa varieties have been developed that are adapted to a wide range of environmental conditions and soil types. Considerable success has also been achieved in breeding for pest and disease resistance. However, alfalfa plants are vulnerable to a number of biotic and abiotic stresses that can limit crop production. One means of ameliorating stresses is by modifying plants by gene transfer techniques. This paper will review some of the recent advances in genetic engineering of alfalfa for improved stress tolerance, specifically: means of transforming alfalfa and gene transfer strategies for increasing tolerance to water deficit, freezing, light deficit, and acid soils. The result of a number of plant stresses is the production of active oxygen species. Expression of a gene encoding superoxide dismutase in transgenic alfalfa is associated with increased tolerance to water deficit and freezing stress. To diminish effects of light deficit on alfalfa leaves, a chimeric gene composed of a senescence-specific promoter fused to a gene for cytokinin synthesis was introduced into alfalfa. As a result, the rate of senescence was reduced in leaves of some plants. Alfalfa roots are sensitive to aluminum present in acidic soils. Transgenic alfalfa plants were produced for increased tolerance to aluminum. These and other results have established that gene transfer techniques are a promising means of improving crop plants for tolerance to stress.