Chlorine gas is an effective alternative to sterilize carnation leaves for Fusarium spp. identification

Abstract

Sterile carnation leaves are required for proper morphological identification of Fusarium spp. but the gamma irradiation equipment required for leaf sterilization is not available to everyone. This study evaluated three different methods for sterilizing carnation leaves: microwave radiation, ultraviolet, and chlorine gas (CG) sterilization. Both microwave and ultraviolet treatments did not sufficiently sterilize leaf tissue, however, exposure to CG for 2 h resulted in no growth of either fungi or bacteria. Exposure times of carnation leaves to CG were also evaluated for spore production, spore size and morphological characteristics of five Fusarium spp. Only carnation leaves exposed to CG for 45, 60 or 90 min were completely free of microorganism contamination. There were some differences in spore production and size, however, no differences were observed for characteristics essential for proper species identification such as micro- and macrospore features and production of sporodochia, perithecia, chlamydospores, and phialides for any of the CG exposure times. This study identified leaves sterilized by CG as a reliable substitute for gamma irradiation sterilization. The method described here is suitable for most laboratories and will provide a means for Fusarium identification when gamma irradiated leaves are not available.