Effects of water activity and temperature on the survival of Aspergillus carbonarius spores in vitro

Abstract

Aims: To determine the effect of water activity (aw) and temperature on the survival of Aspergillus carbonarius spores. Methods and Results: Spores of A. carbonarius were dried onto filter membranes. These filters were held at 1·0, 0·9, 0·8, 0·6 and 0·4 aw and at 1, 15, 25 and 37°C for up to 618 d. At intervals, spores were recovered from filters and assessed for viability by enumeration on dichloran rose bengal chloramphenicol agar. Survival and subsequent growth of spores was prolonged at low temperatures and at aw below 0·6. Above 15°C, 0·6–0·9 aw were often more deleterious than 1·0. However, at 1°C and 1·0 aw, spores lost viability more rapidly than at lower aw. Conclusions: Increased incidence of black Aspergillus spp. in dry soils and from grapes in dry conditions may result partly from prolonged survival of spores. Significance and Impact of the Study: Delineating the direct effect of aw and temperature on survival of A. carbonarius spores may aid in understanding the incidence of this ochratoxin A‐producing species in vineyard soils and on grapes.

A novel fungal fruiting structure formed by Aspergillus niger and Aspergillus carbonarius in grape berries

“…spores are released during summer months and coincide with berry ripening. Leong et al, 2005 also showed that spore presence coincided with the onset of susceptibility to infection by Aspergillus species as did Rooney-Latham et al (2008). The incidence of A. niger and A. carbonarius in vineyards varies with grape maturation, but also with temperature and precipitation.…”

“…Fungal spores survive during spring and summer months either on berries and/or in soil. Studies in Australia (Leong et al 2005) showed that spore dormancy may be associated with survival at low water potential and that spore survival is extended when water potential is low. This may explain the incidence of Aspergillus spp.…”

How will climate change affect mycotoxins in food?

“…These data provide information concerning the ability of A. carbonarius to grow and produce toxin under different ecological conditions, contributing to the development of models for the prediction and risk assessment of ochratoxin A in wine production (Tassou, Natskoulis, Panagou, Spiropoulos, & Magan, 2007). The effect of a w and temperature on the survival of A. carbonarius conidia were determined in an Australian study (Leong, Hocking, & Scott, 2006). Conidia were held at 1.0, 0.9, 0.8, 0.6, and 0.4a w and at 1, 15, 25, and 37°C for up to 618 d. Survival and subsequent growth of spores was prolonged at low temperatures and at a w below 0.6.…”

Further mycotoxin effects from climate change

“…Furthermore, the survival of A.carbonarius conidia was determined in an Australian study (Leong et al, 2006) where survival and growth of spores was prolonged at a w below 0·6 and at low temperatures. Water activities of between 0·6 and 0·9 a w were often more deleterious than 1·0 at above 15°C.…”

“…Fungal conidia are not so resistant as might be expected and of course the asexual forms, which occur in the primary mycotoxin producing fungi, do not produce hardy sexual spores. For example, the Aspergillus carbonarius conidia used in Leong, Hocking, and Scott (2006) were killed in a few hours at 37°C. CC may lead to an expanding range of crop pests and altered transmission dynamics of insects, pests, and plant diseases, which will exacerbate yield reduction and impair food safety (Rosenzweig, Iglesias, Yang, Epstein, & Chivian, 2001).…”