Colonization of grapes berries by Alternaria sp. and their ability to produce mycotoxins

Dana Tančinová,Soňa Felšöciová,Miroslava Cí­Sarová,Zuzana Mašková,Ľubomí­R Rybárik

doi:10.5219/553

Abstract

Our research focused on identify the Alternaria species from grapes (surface sterilized berries and non-surface sterilized berries) of Slovak origin and characterize their toxinogenic potential in in vitro conditions. We analyzed 47 samples of grapes, harvested in years 2011, 2012 and 2013 from various wine-growing regions. For the isolation of species, the method of direct plating berries and surface-sterilized berries (using 1 % freshly pre-pared chlorine) on DRBC (Dichloran Rose Bengal Chloramphenicol agar) was used. For each analysis was used 50 berries. Only undamaged berries have been used for analysis. The cultivation was carried at 25 ±1°C, for 5 to 7 days in dark. After incubation, the colonies of Alternaria were transferred on PCA - potato-carrot agar and CYA - Czapek-yeast extract agar and cultured for 7 days at room temperature and natural light. A total 4 species-groups of the genus Alternaria were isolated from grapes berries: Alternaria alternata (1369 isolates), Alternaria arborescens (734 isolates), Alternaria infectoria (143 isolates), and Alternaria tenuissima (3579 isolates). According to European Union legislation mycotoxins produced by species genus Alternaria are not monitored in foods and food commodities. Mycotoxins such as alternariol and alternariol monomethylether are mutagenic and genotoxic in various in vitro systems. Selected strains were tested for production of altenuene, alternariol monomethylether and alternariol. In neither case of A. infectoria species-group isolates was confirmed the production of tested mycotoxins in in vitro conditions by TLC method. The ability to produce altenuene, alternariol monomethylether and alternariol in in vitro conditions was detected in isolates of Alternaria alternata, Alternaria arborescens and Alternaria tenuissima species-groups. Isolates of Alternaria alternata species-group (44 tested isolates) were able to produce altenuene (24 isolates), alternariol monomethyleter (42 isolates) and alternariol (43 isolates). Only one isolate did not produce any mycotoxins. Isolates of Alternaria arborescens species-group (38 tested isolates) were able to produce altenuene (24 isolates), alternariol monomethyleter (33 isolates) and alternariol (36 isolates). Only two isolates did not produce any mycotoxins. Isolates of Alternaria tenuissima species-group (87 tested isolates) were able to produce altenuene (42 isolates), alternariol monomethyleter (41 isolates) and alternariol (73 isolates). Thirteen isolates did not produce any mycotoxins.

Highlights

Grapes have a complex microbial ecology including filamentous fungi, yeasts and bacteria with different physiological characteristics and effects upon wine production (Barata et al, 2012)
Mycotoxins are secondary metabolites produced by filamentous fungi that have been detected in food commodities, including grapes and wine (Serra et al, 2005)
Our research focused on the identify the Alternaria species from grapes of Slovak origin and characterize their toxinogenic potential in in vitro

Summary

Introduction

Grapes have a complex microbial ecology including filamentous fungi, yeasts and bacteria with different physiological characteristics and effects upon wine production (Barata et al, 2012). Mycotoxins are secondary metabolites produced by filamentous fungi that have been detected in food commodities, including grapes and wine (Serra et al, 2005). RESULTS AND DISCUSSION In the current study from all samples were isolated Alternaria species (from superficially sterilized berries and berries without sterilization, too).

Results

Conclusion