Grafting to improve pathogen and pest resistance of plants

Grafting plants is an opportunity to incorporate important characteristics that allow for the production of a high value crops.  Scion resistance to pests and pathogens can be enhanced by delivery of anti-pathogen/pest factors from selected rootstocks.  Our research is based on the hypothesis that plant inhibitors of pest and pathogen enzymes that contribute to crop damage and disease can provide defenses in roots and be sufficiently and effectively delivered from rootstocks to scion organs, including fruit.  The cell wall pectin-degrading enzyme, polygalacturonase, is produced by fungal pathogens and insect pests to colonize and damage plant tissues.  Plants, however, produce proteins that inhibit pathogen, nematode and insect polygalacturonases and these polygalacturonase-inhibiting proteins (PGIPs) are part of the defenses of fruit and leaves.  Production of these extracellular defense proteins can be enhanced in genetically engineered rootstocks from which they can be transported to scions via the xylem. If this pathogen and pest defense strategy proves to be effective in controlling disease and damage to the whole plant and the fruit products, it is likely to be useful with other grafted horticultural crops using different defense factor combinations.