Predictive modelling of temperature and water activity (solutes) on the in vitro radial growth of Botrytis cinerea Pers

Abstract

The objective of this work was to develop validated models predicting the 'in vitro' effect of a w and temperature on the radial growth of Botrytis cinerea. The growth rate (g, mm d− 1 ) of B. cinerea was calculated at three incubation temperatures (25°C, 15°C, 5°C) and six water activities (ranging from 0.995 to 0.890). The water activity was adjusted with glucose, NaCl, glycerol, or sorbitol. Statistical analysis showed a significant effect of temperature, solute, a w , and their two-and three-way interactions on the growth rate. No growth was observed at a w = 0.93 in the presence of NaCl or at 0.89 in the presence of a non-ionic solute. The maximum colony growth rate decreased when the incubation temperature and water activity was lowered. Secondary models, relating the colony growth rate with a w or a w and temperature were developed. Optimum a w values for growth ranged from 0.981 to 0.987 in glycerol-, sorbitol-, or glucose-modified medium and were close to 1 in NaClmodified medium. A quadratic polynomial equation was used to describe the combined effects of temperature and a w on g (mm d − 1 ) in the presence of each solute. The highest and lowest radial growth rates were observed in models based on glucose and NaCl respectively, whatever the incubation temperature. All models prove to be good predictors of the growth rates of B. cinerea within the limits of experiments. The quadratic polynomial equation has bias factors of 0.957, 1.036, 0.950, and 0.860 and accuracy factors of 1.089, 1.070, 1.120 and 1.260 in media supplemented with glucose, NaCl, glycerol and sorbitol respectively. The results from modelling confirm the general finding that a w has a greater influence on fungal growth than temperature.

A Box-Behnken design for predicting the combined effects of relative humidity and temperature on antagonistic yeast population density at the surface of apples

“…Models based on multi-factor analyses like those described here are valid only for the specific strain/substrate combination studied and within the experimental domain (Delignette-Muller, 1997; Lahlali et al, 2005bLahlali et al, , 2007. Any extrapolation to other strains or growth substrates or beyond the tested ranges of the considered factors would be hazardous.…”

“…Internal validation of prediction accuracy of the BoxBehnken models was based on statistical evaluation of the following tests: Root-Mean-Square Error (RMSE), bias index and accuracy factor, and the lack-of-fit test (Ross 1996;Samapundo et al, 2005;Lahlali et al, 2007). Practical evaluation of the two models was based on a comparison of the responses observed in orchard trials spanning 2 years with the responses predicted on the basis of the models and the measured variables.…”

Enhancement of the biocontrol agent Candida oleophila (strain O) survival and control efficiency under extreme conditions of water activity and relative humidity

“…It is defined as the vapor pressure of water above a sample divided by that of pure water at the same temperature; therefore, pure distilled water has a water activity of exactly one (Hallsworth and Magan, 1996). Water activity (a w ) was modified by the addition of increasing amounts of glycerol to obtain levels of 0.980 and 0.930 at 25°C (Lahlali et al, 2005b(Lahlali et al, , 2006a(Lahlali et al, , 2007a. The a w of all media was measured by a CX 3 Aqua Lab device (Decagon Devices, Inc.).…”

“…In our previous works, the effect of water activity, temperature and relative humidity has been successfully evaluated on the in vitro and in vivo growth of B. cinerea and (Lahlali et al, 2007a(Lahlali et al, , 2006b, P. expansum (Lahlali et al, 2005b(Lahlali et al, , 2006b, P. digitatum and P. italicum (Lahlali et al, 2006a) and Pichia anomala strain K and C. oleophila strain O (Lahlali et al, 2008). The obtained results showed that both antagonistic yeast P. anomala and C. oleophila are highly sensitive to water stress as compared to four Pencillium species and B. cinerea (Lahlali et al, 2007b).…”

Grape berry skin features related to ontogenic resistance to Botrytis cinerea

“…Generally, yeasts are more resistant than bacteria and fungi, i.e they can grow at low Aw values (Rousseau and Donèche 2001). For B. cinerea as for Penicillium spp., it has been shown in vitro that a high free water level is necessary to induce spore germination and fungal growth (Lahlali et al 2007;Magan and Lacey 1984).…”