Submitted to: American Phytopathological Society
Publication Type: Abstract Only
Publication Acceptance Date: 4/6/2004
Publication Date: 6/15/2005
Citation: Phytopathology 95(6, supplement):S155
Technical Abstract: An isolate of Colletotrichum gloeosporioides (Cg), which kills Russian thistle (RT, Salsola tragus), is being evaluated for use in biological control. Host range tests indicate minor infection of closely related Salsola spp., and there was limited symptom development on senescent spinach. No symptoms developed on young (non-flowering) spinach, while inoculations with C. dematium, a U.S. spinach pathogen, under the same conditions clearly damaged the plants. This suggests a possible hemibiotrophic disease response in spinach (i.e., symptom development after an extended latent period), something not uncommon among species of Colletotrichum. In research with other Colletotrichum species, latent or "symptomless" infections have been reported after induction of artifical senescence following treatment of plants with paraquat. Similar "symptomless" responses have been noted for at least three crop species in the current host range determination of Cg from RT. Truly latent infections are considered "no risk" regarding evaluation of this candidate, but the hemibiotrophic response complicates the host range determination and it raises issues concerning risk.