In vitro effect of some fungicides on growth and aflatoxins production by Aspergillus flavus isolated from Capsicum powder

Abstract

The aim of this study was to determine the effect of some pre-harvest fungicides on growth and aflatoxin (AF) production of three Aspergillus flavus strains found in Capsicum powder. Each isolate, previously isolated from paprika, chilli and smoked paprika, was inoculated on yeast extract sucrose agar and on a 3% paprika extract agar medium supplemented with different fungicides and incubated at 20 and 30°C during 7 days. Growth measurements were obtained on days 3, 5 and 7, and the AF production was determined on day 7. The significance of the effects of the factors (strain, medium, temperature, time and fungicides) and their interaction over colony diameter and AF production was determined. Temperature constrained the effectiveness of fungicides in reducing growth, the fungicides being most effective at 20°C. The efficacy of the fungicides over AF production depended on the medium used and temperature. The most effective fungicides in inhibiting growth and AF production, regardless of the strain tested or applied conditions, were tebuconazole 25% and mancozeb 80% applied at a concentration of 0.75 and 3.5 g l⁻¹, respectively. Care should thus be taken in the choice of a suitable fungicide because their effectiveness may depend on intra-specific variation and temperature. Moreover, it is necessary to take into account that the most efficient fungicide in reducing growth is not always the best choice for pre-harvest treatments because it may promote AF production. Thus, the best fungicide is the one that can simultaneous prevent growth and AF production.

Keywords:

• Aspergillus flavus
• growth
• aflatoxins
• fungicides

Acknowledgements

The authors are grateful to the Spanish (Project Number AGL2007-66416-C05-03) and Catalonian (XaRTA – Reference Network on Food Technology) governments for financial support. The authors would like to thank X. Ochoa de Eribe (research and development technician of SIPCAM INAGRA) and Bayer CropScience S.L. for supplying some of the fungicide samples, and also R. Miranda for the grammatical review.