Biological control of Botrytis cinerea growth on apples stored under modified atmospheres

The combined effect of modified-atmosphere packaging and the application of a bacterial antagonist (Erwinia sp.) on Botrytis cinerea growth on apples (cv. 'Golden Delicious') was investigated. Inoculated apples were stored in polyethylene bags at 5 degrees C. The initial gas composition in each bag was set according to a central composite experimental design involving five levels of O-2 (1 to 15%) and CO2 (0 to 15%). Control samples under ambient conditions were also included. Without the antagonist, measurements of mold colony diameter over time showed that O-2 had no effect on the growth of B. cinerea, while increased CO2 levels delayed its growth by about 4 days. Application of the antagonist resulted in a significant interaction between O-2 and CO2. At low O-2 levels, CO2 had no effect on mold growth, but at high O-2, CO2 enhanced mold growth. O-2 and the antagonist worked synergistically to reduce mold growth by about 6 days at low levels of CO2. However, at high CO2 levels, O-2 had no effect. The strongest antagonistic effect was observed under ambient conditions. Overall, results showed that high CO2 atmospheres can slow the growth of B. cinerea and that Erwinia sp. was an effective antagonist against B. cinerea growth on apples, particularly under ambient conditions.