THE UTILITY OF A PARAQUAT-BASED TECHNIQUE FOR HOST RANGE TESTING OF CANDIDATE FUNGAL BIOLOGICAL CONTROL AGENTS OF WEEDS

Abstract

An exotic isolate of Colletotrichum gloeosporioides, (FDWSRU #96-067) from Hungary is highly pathogenic on Russian thistle (Salsola tragus, type-A). To be considered for release as a fungal biological control organism, it is imperative that this fungal isolate not be pathogenic to non-target plant species. A Paraquat Method is examined here within a specific time frame post-inoculation to determine whether it is a valid and improved approach to host-range testing. Fungal development was measured in cleared sections of inoculated Salsola tragus, type-A, and soy bean leaves (Glycine max) treated with, or without paraquat. Effects of excision were also measured as part of this study. Results indicate no difference in pathogen development for paraquat treated leaves at 48 hours after inoculation compared to no paraquat 72 hours after inoculation. For the time frame delineated in this experiment, the paraquat technique is rejected as a diagnostic tool.