Detection, quantification and biological control of post-harvest pathogens of pome fruit

Blue mold (Penicillium expansum), grey mold (Botrytis cinerea) and mucor rot (Mucor piriformis) are important post-harvest diseases of pome fruit in British Columbia and throughout the world causing annual losses of 5 – 20%. Identification and quantification using novel DNA macroarray technology may assist in the development of prediction models and disease forecasting. Post-harvest pathogens were monitored and quantified throughout the growing season in four apple orchards in the Okanagan Valley, BC in 2007 and 2008. Their detection was variable due to field and year differences. The average percent detection of P. expansum (27.4%) and M. piriformis (19.2%) was higher than that of B. cinerea (6.2%). There was a positive correlation between total post-harvest pathogen detection in aerial samples just prior to harvest and after harvest in naturally infected fruit (r = 0.74; p = 0.09). Pseudomonas fluorescens (isolates 1-112, 2- 28, 4-6) and Serratia plymuthica (isolate 6-25), isolated from the rhizosphere of legumes, were investigated for their biological control capabilities in semi-commercial storage conditions at 1°C in air and commercial storage conditions in controlled atmosphere and with 1-methylcyclopropene (1-MCP) application. Overall, isolate 6-25 provided control in the greatest number of treatments (51.7%) while isolate 1-112 provided the greatest level of control (75.8%) in treatments where significant control was exhibited. Isolate 4- 6 was tagged with green fluorescent protein to gain insight into bacterial antagonist population and survival dynamics. Alone, its population increased 10 fold after 30 d in storage at 1°C and then decreased to concentrations similar to those at inoculation. In the presence of the pathogen, 4-6-gfp increased then decreased after 30 d in storage at 1°C to undetectable amounts. These data provide greater insight into the prediction, control and population dynamics of pathogens and biological control agents as a means of preventing and controlling post-harvest storage diseases in pome fruit.Arts and Sciences, Irving K. Barber School of (Okanagan)Biology, Department of (Okanagan)Graduat