Plant & Animal Genomes XI Conference Plant & Animal Genomes XI ConferenceJanuary 11-15, 2003
Town & Country Convention Center
San Diego, CA
Workshop: Fruit and Nut Crops
To show that genetic engineering (GE) could be used to create strains of apple cvs with increased resistance to fire blight (Erwinia amylovora), the apple cv Royal Gala (RG) was transformed using Agrobacterium with genes for several heterologous lytic proteins (LP), driven by constitutive promoters. RG lines transgenic for attacin showed elevated FB resistance and normal RG fruit quality during up to 4 years of field trials. Attacin-transgenic lines of Galaxy and M.26 rootstock have also shown increased FB resistance in the field. The individual fruit color patterns of RG and Galaxy were maintained in the transgenic lines. RG lines transgenic for LP's SB-37, and avian and T-4 lysozyme had increased FB resistance, but were generally less resistant than attacin-transgenic lines. The GE technology is now being applied with genes designed for more ready acceptance by regulatory agencies, apple growers, and consumers. E. amylovora produces an effector protein harpin, which induces resistance when applied topically to apple flowers. Some apple lines transgenic for the harpin gene (HrpN), driven by an inducible promoter were shown to have increased FB resistance in growth chamber and preliminary field tests. The NPR1 protein, thought to be pivotal in the plant disease resistance cascade, when over-expressed in Arabidopsis has increased disease resistance. Apple lines transgenic for the apple MpNPR1 gene (S. He) are being evaluated for resistance in the growth chamber. Another strategy involving silencing of apple kinases thought to be involved in FB pathogenesis is described in an abstract by X. Meng et al.