Pathogenic and parasitic organisms can have profound impacts on the ecology of their hosts.  In plant systems, several recent studies have documented effects of pathogens on host plant traits that influence interactions between hosts and other organisms, including insect herbivores and disease vectors.  In this study, we explore how pathogen infection of host plants affects host selection and utilization by the parasitic plant Cuscuta pentagona (field dodder).  Previous work in our lab has shown that C. pentagona seedlings use host plant odor cues (which are likely to be influenced by pathogen infection) to locate and discriminate among hosts, and dodder vines are known to vector some plant pathogens, but the disease ecology of these interactions is largely unexplored.  We are examining how bacterial and viral infections alter the odor cues presented to foraging C. pentagona seedlings, the effects of these changes on host selection, and whether differences in seedling attraction to healthy and infected hosts correspond to differences in the performance of the parasite following attachment.

Results/Conclusions

Our initial results demonstrate that C. pentagona seedlings respond to the odors of healthy (mock-inoculated) tomato plants in preference to those of plants infected with bacterial speck (Pseudomonas syringae pv. tomato DC3000).  The cues driving this preference are not yet established, though we observed a trend toward lower volatile emission from infected plants.  We are currently exploring differences in the performance of the parasite on healthy and infected plants and are conducting similar analyses using a second pathogen (Cucumber mosaic virus), which previous work in our lab has shown to elevate volatile emissions in a number of plant species.  This research will enhance our understanding of the chemical ecology of plant pathogens, which is poorly known, and of the factors influencing host location and selection by parasitic plants.