Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2001
Publication Date: 5/1/2002
Interpretive Summary: Genetic biotechnology promises the development of barley plants with enhanced abilities to resist pests and environmental stress, and to produce food with better nutritional qualities. The procedures used to genetically engineer plants, however, require improvement. One problem is that the tissue culture systems necessary to produce transgenic plants impose stresses on cultured cells. These stresses cause undesirable mutations, which generally result in plants, which are less healthy and produce less seed. The problem, then, is not that these plants are environmentally hazardous, but that their impaired health is incompatible with the farmer's needs of high yields and quality, which are essential to profitability. The research reported here examined three different systems, developed by the authors, for culturing barley cells. It was discovered that the newly developed culture systems were successful produced healthier plants that those developed using traditional methods. These new systems should be a valuable step forward in meeting the ultimate goal of genetic engineering, which is to make precise, controllable changes without disturbing other characteristics that control the utility and safety of common food crops.
Technical Abstract: Modern plant breeding programs depend heavily on germplasm resources composed of closely-related breeding lines and cultivars. Asexual introduction of recombinant DNA offers novel opportunities for crop improvement, but most transformation methods rely on tissue culture systems, which are mutagenic. The resultant transgenic plants frequently contain undesirable genetic changes (somaclonal variation), in addition to the introduced transgene. Such plants may have reduced agronomic performance, which complicates their use as parents in a breeding program. The development of tissue culture systems that are less mutagenic should enable the production of transgenic plants with superior performance. In this study, agronomic traits were measured for plants regenerated from cultures of two barley genotypes, using three different tissue culture systems, and compared to the performance of uncultured controls. Plants derived from all three systems were shown to have reduced performance for one or more agronomic traits, but there were clear differences attributable to the culture system. Plants derived from standard embryogenic callus tissues were shown to have the greatest reductions in agronomic performance. Two other tissue culture systems, which had been developed for increased regenerability, showed better performance. Plants derived from highly differentiated, meristematic tissues showed the least reductions in agronomic performance. Plants derived from a modification of the embryogenic callus system--which is characterized by an intermediate level of differentiation--showed intermediate levels of agronomic performance.