Lahlali Rachid, Massart Sébastien, Serrhini M Najib, Jijakli M Haïssam
Unité de Phytopathologie, Faculté Universitaire des Sciences Agronomiques de Gembloux, Passage des Déportés 2, 5030 Gembloux, Belgium.
Int J Food Microbiol. 2008 Feb 29;122(1-2):100-8. doi: 10.1016/j.ijfoodmicro.2007.11.053. Epub 2007 Nov 29.
The objective of this work was to develop models predicting the combined effects of relative humidity (RH, 75-98%), temperature (5-25 degrees C), and initial applied yeast concentration (10(4)-10(8) CFU/ml) on the apple-surface population densities of two biocontrol agents fused against postharvest diseases; the antagonistic yeasts Pichia anomala strain K and Candida oleophila strain O. Experiments were carried out according to a Box-Behnken matrix. Multiple regression analyses showed that both models yielded a good prediction of yeast density. The effect of relative humidity appeared greater than that of temperature. The number of yeast colony-forming units per square centimeter of apple fruit surface increased with increasing relative humidity, temperature, and initial applied yeast concentration. The models predict that under optimal growth conditions (25 degrees C, 98%), strains O and K should reach a density of 10(4) CFU/cm2 when applied initially at 2 x 10(7) (strain O) or 10(7) CFU/ml (strain K). The model results suggest that rainfall was likely the principal cause of the variability of yeast efficacy reported for previous preharvest orchard trials spanning two successive years. Temperature may also contribute to this variation. The models developed here are important tools for predicting population densities of both strains on the apple surface within the experimental limits. The use of these results should contribute to achieving yeast densities of 10(4) CFU/cm2 on apples by controlling yeast application and environmental factors such as relative humidity and temperature. The results of this study also confirm our previous in vitro findings that water activity has a greater effect than temperature on yeast population density.
这项工作的目的是建立模型，预测相对湿度（RH，75 - 98%）、温度（5 - 25℃）和初始接种酵母浓度（10⁴ - 10⁸ CFU/ml）对两种用于防治采后病害的生防菌在苹果表面种群密度的综合影响；这两种拮抗菌为异常毕赤酵母菌株K和嗜油假丝酵母菌株O。实验按照Box - Behnken矩阵进行。多元回归分析表明，两个模型对酵母密度都有良好的预测效果。相对湿度的影响似乎大于温度。每平方厘米苹果果实表面的酵母菌落形成单位数量随着相对湿度、温度和初始接种酵母浓度的增加而增加。模型预测，在最佳生长条件下（25℃，98%），当初始接种量为2×10⁷（菌株O）或10⁷ CFU/ml（菌株K）时，菌株O和K应达到10⁴ CFU/cm²的密度。模型结果表明，降雨可能是此前连续两年采前果园试验中报道的酵母防治效果差异的主要原因。温度也可能导致这种差异。这里建立的模型是预测在实验范围内两种菌株在苹果表面种群密度的重要工具。利用这些结果，通过控制酵母接种量以及相对湿度和温度等环境因素，应该有助于在苹果上实现10⁴ CFU/cm²的酵母密度。本研究结果也证实了我们之前的体外研究结果，即水分活度对酵母种群密度的影响大于温度。
