Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2008
Publication Date: 8/1/2008
Citation: Nagel, A., Schnabel, G., Petri, C., Scorza, R. 2008. Generation and characterization of transgenic plum lines expressing the Gastrodia anti-fungal protein. HortScience. 43:1514-1521. Interpretive Summary: The use of genetic engineering (GE) to increase disease resistance in agricultural crops is becoming a viable complementary technique to traditional disease management methods. The total area devoted to growing GE crops has seen a significant increase in the past decade. This increase has been mostly in field crops, such as soybean, corn and cotton, but few horticultural crops have benefited from this technology. We have evaluated the ability of a natural disease resistance gene isolated from an Asian orchid to produce disease and nematode (microscopic worms that feed on tree roots) resistance in fruit trees using plum as the model for other fruit tree species. We have shown in our report that this gene, the Gastrodia anti-fungal protein (GAFP) gene, increased resistance in plum to a disease produced by a fungus (Phytopthora) and to a nematode that causes serious root damage to fruit crops. Our work shows that the GAFP gene has the potential for developing fruit tree rootstocks that are root disease and nematode resistant. Non-genetically engineered varieties could be grafted onto these genetically engineered resistant rootstocks to produce trees that would survive longer and require less pesticide use for the production of fruit.
Technical Abstract: The Gastrodia anti-fungal protein (GAFP) is a monocot mannose-binding plant lectin isolated from the Asiatic orchid Gastrodia elata. This lectin has provided documented disease resistance in transgenic tobacco and cotton against several root diseases, but it's potential to confer disease resistance to tree species is not known. Using Agrobacterium tumefaciens-mediated transformation, we obtained four transgenic plum (Prunus domestica) lines. Three transgenic lines (designated 4J, 4I, and 5D) were used for further analysis. All transgenic lines produced GAFP in root and leaf tissue, and Southern blot analysis revealed that lines 4J, 4I, and 5D possessed one, two, and four copies of the GAFP-1 gene, respectively. Lines 4J and 4I were not phenotypically different from the control, but line 5D showed significant divergence from these lines with regard to its leaf morphology and growth habit. All transgenic lines demonstrated increased resistance to selected, agriculturally important plum diseases, but the effects were not always consistent between lines. Compared to the inoculated control, line 4J exhibited increased resistance to Phytophthora root rot, caused by P. cinnamomi, and the root-knot nematode, Meloidogyne incognita. Line 4I showed increased resistance to white rot (Sclerotium rolfsii) and the root-knot nematode but not to Phytophthora root rot. Line 5D only demonstrated increased resistance to the root-knot nematode. None of the transgenic lines were resistant to the ring nematode, Criconemoides xenoplax. In this study, we document the first evidence that a plant lectin, such as GAFP, can confer increased levels of resistance to agriculturally important plant pathogens in a tree species.