Winsor, James , Sasuclark, Miruna A , Stephenson, Andrew G. .
Floral transmission of bacterial wilt disease in Cucurbita texana.
Many plant pathogens are vectored by insect herbivores. In the genus Cucurbita, the bacterium Erwinia tracheiphila causes wilt disease, which is economically devastating to cultivars and also attacks wild species. Erwinia is vectored by the specialist herbivores Acalymma and Diabrotica (Coleoptera) which feed on foliar tissue and transmit the bacterium through fecal matter. Our studies of C. texana, a wild gourd, show no difference between inbred and outbred lines in susceptibility to the pathogen when it is injected into stem and foliar tissue. However, in the field, inbred lines were significantly less likely to develop wilt disease (in three of the four years studied), even though they suffered greater herbivore damage over the growing season (p< 0.04). This paradox is explained by transmission of the pathogen through floral tissue: outbred plants produced greater numbers of flowers, in which the beetles congregate; they produced significantly higher levels of attracting volatiles (e.g., 1,2,4-trimethoxybenzene); and attracted greater numbers of beetles to their flowers. Greenhouse studies showed that 23% of plants inoculated with Erwinia suspension through staminate flowers and 31% of plants inoculated through pistillate flowers developed wilt disease, and fluorescence studies of GFP-transformed Erwinia show that the bacterium entered flowers through the nectaries and traversed the peduncle to the stem within two days. Our data demonstrate another example of the risk of reproduction and suggest that the trade-off between reproduction and pathogenicity warrants greater attention.
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1 - The Pennsylvania State University, Department of Biology, 3000 Ivyside Park, Altoona, PA, 16601, USA
2 - The Pennsylvania State University, Department of Biology, 202 Mueller Laboratory, University Park, PA, 16801, USA
bacterial wilt disease
Presentation Type: Oral Paper:Papers for Sections
Location: Council Chambers/SUB
Date: Monday, July 28th, 2008
Time: 2:45 PM