Trichothecenes and mycoflora in wheat harvested in nine locations in Buenos Aires province, Argentina.

A total of 120 freshly harvested wheat samples from the 2004 season in nine locations from Northern Buenos Aires Province, Argentina, were analysed for trichothecene natural occurrence and associated mycoflora, and for determining the influence of commonly used fungicide field treatment and the cultivar type on trichothecene contamination. The trichothecenes T-2 tetraol, T-2 triol, HT-2 and T-2 toxin (HT-2, T-2), diacetoxyscirpenol (DAS), nivalenol (NIV), deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON) and 15-acetyldeoxynivalenol (15-ADON) were analysed by gas chromatography and electron capture detection. Detection limits ranged from 4 to 20 microg/kg. The isolation frequencies of species were calculated. Alternaria alternata, Fusarium graminearum, Fusarium poae and Fusarium semitectum were the predominant fungal species identified as endogenous mycoflora. The type of cultivar and the fungicide field treatment did not affect significantly the trichothecene contamination. The trichothecenes type A detected were HT-2 and T-2 triol toxins and the type B were DON, NIV and 3-ADON. Based on 120 samples the incidences were 21.7% for 3-ADON, 22.5% for HT-2, 27.5% for T-2 triol and 85% for DON. NIV was confirmed in one sample. Mean levels of trichothecene positive samples were between 7 and 2788 microg/kg.

Mycoflora and potential for mycotoxin production of freshly harvested black bean from the Argentinean main production area.

A mycological survey was carried out, for the first time, on black bean samples from the northwestern Argentinean province of Salta in the 1999 harvest season. Ten varieties of black beans were evaluated at three locations. Species of the genus Alternaria were the most prevalent component of the black bean mycoflora. Species of Fusarium, Sclerotinia, Rhizoctonia and Acremonium were also recorded. The predominant species of the genera isolated were Alternaria alternata, Sclerotinia sclerotiorum, Rhizoctonia solani, Fusarium semitectum and Acremonium strictum. An analysis of variance was applied to determine possible differences between black bean varieties. Variety FT88/519 was the most susceptible to Sclerotinia sclerotinia infection, while the variety DOR 604 was the least susceptible. As toxigenic species were recovered, Alternaria toxins, zearalenone and trichothecenes may pose a contamination risk for black bean.

Fungi associated with food and feed commodities from Ecuador.

Freshly harvested soybean, rice and corn from farms and corn-based pelleted feeds were collected from ranches from the coastal and mountain regions in Ecuador during 1998, and assessed for fungal contamination. The most prevalent fungi on pelleted feed were Aspergillus flavus and Fusarium graminearum. The prevalent fungi recovered from soybean were F. verticillioides, F. semitectum, Aspergillus flavus and A. ochraceus. In rice, F. oxysporum was the most prevalent toxigenic fungal species recorded, followed by F. verticillioides and A. flavus. In corn, F. verticillioides was the most prevalent fungus isolated in both the coastal and mountain regions, with high isolation frequencies of A. flavus and A. parasiticus at the coast. Based on the toxigenic species recovered, ochratoxin A may pose a contamination risk for soybean. A higher probability of aflatoxin contamination of corn was found in the coastal samples compared to those of the mountain region, while a risk of fumonisin contamination of corn exists in both regions.

Distribution of fumonisins in dry-milled corn fractions in Argentina.

Corn samples and different dry-milled fractions collected from an industrial mill in Argentina were analysed. Average contaminations were FB(1) 1540 microg kg(-1), FB(2) 716 microg kg(-1) and FB(3) 152 microg kg(-1) in whole corn; FB(1) 135 microg kg(-1), FB(2) 39.1 microg kg(-1) and FB(3) 10.2 microg kg(-1) in corn grits; FB(1) 358 microg kg(-1), FB(2) 122 microg kg(-1) and FB(3) 45.9 microg kg(-1) in 'C' flour; FB(1) 148 microg kg(-1), FB(2) 52.5 microg kg(-1) and FB(3) 28.3 microg kg(-1) in corn meal; and FB(1) 4210 microg kg(-1), FB(2) 2010 microg kg(-1) and FB(3) 447 microg kg(-1) in germ and bran together. The fumonisin contamination level was approximately three times higher in germ and bran than in whole corn, 13 times higher than in 'C' flour and 29 times higher than in corn meal and corn grits. Taking into account the distribution of fumonisins in commercial dry-milled corn fractions and corn meal consumption in Argentina, a theoretical whole corn level of 6640 microg kg(-1) maximum of total fumonisins could be processed to obtain products considered safe for human health.

Natural occurrence of mycotoxins and mycoflora of argentinien popcorn.

Argentina is the first popcorn exporting country worldwide. In 1997-1998 harvest season, 40,000 ha were sown with a production of 125,000 tons; 120,000 tons of this production were exported to more than 40 countries. The objectives of this study were to isolate and to identify the fungi present in this cereal and to assess the occurrence of mycotoxins in freshly harvested popcorn in Buenos Aires province, Argentina, in 1999. All popcorn samples showed fungal contamination. A total of 4,211 isolates were recovered from popcorn kernel samples. The prevalent species isolated wasFusarium verticillioides followed byPenicillium funiculosum, F. graminearum andAlternaria alternata. No aflatoxins, zearalenone, deoxynivalenol or ochratoxin A were detected in the 42 popcorn simples. All samples but one were contaminated with fumonisins (FB) in a range in ug/kg of (not detected-529) for FB1; (not detected-216) for FB2 and (not detected-103) for FB3. Fumonisin contamination levels in Argentinean popcorn were lower than observed in flint corn. No significant differences in fungal and fumonisins contamination levels were observed in the different tested hybrids.

Mycoflora of freshly harvested flint corn from Northwestern Provinces in Argentina.

A mycological survey was carried out for the first time, on red flint corn samples from the northwestern Andinian region of Argentina in the 1999 and 2000 harvest seasons. Species of the genus Fusarium were the most prevalent component of the flint corn mycoflora present in all provinces. F. verticillioides was the predominant Fusarium isolated in the 1999 harvest season in the the region, and was found at higher incidence level than those observed on commercial semident corn hybrids harvested in the main corn production area in Argentina (Pampean region). During the 2000 harvest season, Fusarium graminearum was most commonly isolated species in Salta province.

Influence of Inoculum Preparation and Volume on Growth of Mycotoxigenic Molds.

The influence of the volume and the aw of the inoculum, adjusted or not with glycerol to the aw of the medium, on growth of mycotoxigenic species of fungi was determined for Aspergillus flavus , Aspergillus ochraceus , Penicillium citrinum , Penicillium viridicatum , Fusarium tricinctum and Microdochium nivale . Statistical analysis of the data was based on the application of multivariate techniques. It was seen that at constant volumes (10 µl), P. viridicatum , A. ochraceus and M. nivale show no significant growth differences whether or not the aw of the inoculum is adjusted; but significant differences were observed with A. flavus , P. citrinum and F. tricinctum . Moreover, significant differences in growth between adjusted and unadjusted aw levels are also present when there are different inoculum volumes for A. flavus and P. citrinum . Thus, it is appropriate to adjust the inoculum to the same aw level as that of the medium or the food to be considered. In all cases, where significant differences were present, greater colony diameters were observed when the aw was adjusted. With the same inoculum preparation, different inoculum volumes also affect fungus growth, producing greater colony diameters with increments in the volume.