Impact of non-selective fungicides on the growth and production of ochratoxin A by Aspergillus ochraceus and A. carbonarius in barley-based medium

Abstract

The aim of this study was to assess the influence of the non-selective fungicides mancozeb, copper oxychloride, and sulfur on the growth and capability for producing ochratoxin A (OTA) of ochratoxigenic isolates of Aspergillus carbonarius and A. ochraceus in barley-based medium. Lag phases and growth rates were determined for each fungicide at different doses, at 15°C and 25°C and at 0.97 a_w . Mancozeb at 40 mg l⁻¹ inhibited fungal growth and provided lag phases >24 days at 10–20 mg l⁻¹ and 15°C. OTA was observed only at 25°C and doses <10 mg l⁻¹. At 15°C, copper oxychloride proved inhibitory at 800 mg l⁻¹, while at 25°C growth was not delayed and only high doses decreased OTA levels. Sulfur was inhibitory or provided large lag phases at 5–8 g l⁻¹ (at 15°C) while at 25°C growth took place even at 8 g l⁻¹, although OTA levels were low or undetectable. The antifungal activity decreased in the order mancozeb > copper oxychloride > sulfur, and was lower at 25°C than at 15°C. OTA accumulation was affected by the type of fungicide, dose, temperature and time. The efficacy of these fungicides on the growth of A. carbonarius and A. ochraceus and OTA production in barley-based medium is assessed for the first time.

Keywords:

• mycology
• microbiology
• high-performance liquid chromatography (HPLC)
• mycotoxins
• ochratoxin A
• cereals

Acknowledgements

The authors acknowledge financial support from FEDER, the Spanish Ministry of Science and Innovation (Project Number AGL2007-66416-C05-01/ALI and a research grant) and from the Valencian Government ‘Conselleria d’Empresa, Universitat i Ciencia’ (Project Number ACOMP/2009/371).