Chemical ecology of host/vector/pathogen interactions in the wild gourd Cucurbita pepo texana

Many of the most ecologically and economically important diseases of plants are vectored by insects, and the spread of these diseases ultimately depends on complex interactions among plants, pathogens, and insect vectors. However, empirical evidence demonstrating mechanisms by which vector behavior mediates pathogen spread from infected to healthy hosts and how multiple plant diseases interact in natural populations is sparse. Here, we investigate the role of pathogen-induced volatiles from leaves and flowers of the wild gourd Cucurbita pepo texana infected with the bacterial wilt pathogen Erwinia tracheiphila and Zucchini Yellow Mosaic Virus (ZYMV) on the on the attraction of striped cucumber beetle vectors, Acalymma vittatum, which vector wilt disease. Floral and leaf volatile collections were taken from healthy and pathogen-infected gourd plants in the greenhouse and natural field conditions. These results show that volatiles from leaves on ZYMV-infected plants are indistinguishable from volatiles released by leaves on healthy plants, but symptomatic leaves on Erwinia tracheiphila-infected plants release significantly more volatile compounds, including unique pathogen-induced volatiles that are not present in the volatile profiles from mock-inoculated plants. In contrast, male flowers on wilt-infected and ZYMV-infected plants release significantly lower amounts of a similar volatile blend than male flowers on healthy plants. Consequences on beetle vector behaviour of the different volatile profiles from healthy and pathogen-induced plants and how pathogen-induced volatiles may affect rates of co-infection with both diseases in a shared plant host in field settings will be discussed.