Submitted to: American Phytopathology Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2006
Publication Date: N/A
Technical Abstract: A strong international effort to isolate and introgress resistance genes for grapevine powdery mildew is currently hampered by lack of precise characterization of the mechanisms of resistance, which could provide insight into inheritance and durability. In this study, four grapevine genotypes with different levels of resistance were analyzed using light microscopy for the precise timing and mechanism of resistance. Infection progress on the second and fourth fully expanded leaves was analyzed to discern the effect of host development on resistance mechanisms. The proportion of conidia forming appressoria and singular or multiple secondary hyphae at 12, 36, and 60 hours post-inoculation was recorded along with the presence of a visible host response to provide initial insight into the mechanism and timing of resistance. Subsequently, haustoria were visualized using confocal microscopy to determine whether resistance prevented penetration. The four genotypes developed various degrees of ontogenic resistance in the fourth leaf relative to the second leaf. Colonization at 8 days post-inoculation corresponded to cellular resistance phenotypes. This quantitative approach could aid the detection of quantitative resistance loci and characterization of qualitative hypersensitive and prehaustorial resistance.