Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2011
Publication Date: 8/15/2011
Citation: Gautam, D., Ma, L., Bruton, B.D., Fletcher, J. 2011. Erwinia tracheiphila colonization of cantaloupe fruits through flower inoculation [abstract]. 2011 American Phytopathological Society (APS)-International Plant Protection Congress (IPPC) Joint Meeting. 101:S59. Interpretive Summary:
Technical Abstract: Cantaloupe (Cucumis melo var. cantalupensis) is a nutritious fresh fruit. Bacterial wilt, caused by Erwinia tracheiphila, is the most devastating cantaloupe disease globally. The pathogen is transmitted in nature by xylem-feeding spotted and striped cucumber beetles; other modes of infection have not been reported. We hypothesized that E. tracheiphila can enter cantaloupe plants through flower nectarthodes and/or pollen tubes and thereby contaminate fruit interiors and move systemically in the plant. Newly opened hand pollinated hermaphrodite/female cantaloupe flowers were inoculated with 5µl of either E. tracheiphila (10**7, 10**8, 10**9 or 10**10 cfu/ml) or peptone buffer (controls) by placinginoculum drops onto stigma tops and onto the nectaries. Eight of 9 E. tracheiphila inoculated plants showed wilting of part or all of the vines. Fruits on three inoculated plants developed small-to-large watersoaked spots on the rind at 18 or more days post-inoculation. Peduncles collapsed, and further rind netting and fruit development was impaired on these fruits. Off-white ooze was observed on spotted fruit, the bacterial slimy string test was positive and bacteria streamed from cut stems and peduncles immersed in water, symptoms characteristic of bacterial wilts. This is the first report of infection and symptom development on cantaloupe fruits following flower inoculation with E. tracheiphila. Whether flower invasion is a significant mechanism of infection in a field setting is not known.