SORBITOL HAS NO ROLE IN FIRE BLIGHT AS DEMONSTRATED USING TRANSGENIC APPLE WITH CONSTITUTIVELY ALTERED CONTENT

Sorbitol content in apple tissues has long been implicated in fire blight susceptibility. Content fluctuates according to plant growth stage during the season, and the link has been based on largely empirical evidence of differences in relative sorbitol measurements in infected and non-infected trees. We inoculated transgenic 'Greensleeves' apple trees with constitutively repressed (2 lines) or increased (1 line) sorbitol content. Sorbitol content did not have a major influence on disease severity or progression regardless of pathogen genotype (6 Erwinia amylovora strains and 1 Erwinia pyrifoliae) or inoculum concentration.