Submitted to: Journal of American Society of Horticulture Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 25, 1999
Publication Date: N/A
Interpretive Summary: Most pear varieties grow vigorously, and result in large trees which are difficult and expensive to prune, harvest, and spray. In apples, the use of dwarfing rootstocks and naturally occurring mutations in popular varieties has resulted in smaller trees which are easier and less expensive to manage, and which allow more fruit production on the same amount of land. Dwarfing rootstocks adapted to U. S. production areas and mutants which result in smaller productive trees are lacking for pear. When genetically engineered into several other plant species, the rolC gene has been shown to produce alterations in growth and development which result in smaller plants. Our objective was to genetically engineer the rolC gene into 'Bartlett' and 'Beurre Bosc', two of the pear varieties which account for over 70% of the pears grown in the U.S. We have been successful in inserting the gene into 'Beurre Bosc', and three independent "transgenic" variants of this variety have been obtained. This is the first report of genetic engineering of pear with a gene of potential economic benefit, and the first report of genetic engineering of 'Beurre Bosc'. Preliminary measurements of the transgenic plants indicate that the gene causes a reduction in height. Further experiments are planned to determine the usefulness of rolC transgenic plants for improving the efficiency of pear production.
Technical Abstract: 'Beurre Bosc' pear was transformed with Agrobacterium tumefaciens strain EHA101 containing the binary vector pGA-GUSGF into which the rolC gene had been inserted. Leaf explants from in vitro shoot tip cultures were wounded, Agrobacterium-inoculated, and grown on kanamycin selection medium. Regenerating shoots were transferred to proliferation medium without antibiotics. Three clones tested positive for GUS and nptII. Transformation with the rolC gene was confirmed by DNA, RNA, and protein blot analyses. The number of copies of the rolC transgene varied from 1 to 3. Plantlets of the three transgenic clones were acclimated and transferred to the greenhouse. Preliminary observations of phenotype indicate that the rolC gene has resulted in a reduction in height and number of nodes in transgenic 'Beurre Bosc'.