| Summary: | 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.
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