Low temperature stored Botrytis cinerea in cryobank maintains pathogenicity in grapevine

Grey mould or bunch rot caused by the fungus Botrytis cinerea is the major cause of fruit and wine losses for the fast-growing New Zealand grapevine industry. The cost of Botrytis rot to the industry worldwide is also enormous. In a collaborative project we have developed protocols for somatic embryogenesis in grapevine and this system is now in use for inducing mutations and selecting for fungal pathogen resistance using toxins from Botrytis. The availability of pathogenic cultures of Botrytis throughout the year facilitates rapid screening and evaluation of genotypes. For long-term maintenance, we suspended fresh Botrytis cultures from potato dextrose agar (PDA) plates in Cryobank® beads in glycerol and maintained them at -20°C. The stored cultures were retrieved after more than one month and their pathogenicity was tested on leaves from in vitro-grown susceptible cultivars. Results indicate that the strains maintain the same pathogenicity as the original cultures. This method of cold storage is therefore more effective for maintaining B. cinerea cultures than on PDA plates at low temperatures. The latter method requires frequent subculture and often results in loss of pathogenicity of the original isolates.