H.H.L. González

Mycoflora of Argentinian corn harvested in the main production area in 1990

Corn (Zea mays) is the main cereal produced in and exported from Argentina. The risk of contamination by mycotoxins is related to the mycoflora associated with the corn kernels. This paper reports on the identification of internal and external mycoflora of corn kernels harvested in the main production area in Argentina in 1990. A mycological survey was carried out on 178 corn samples, from five locations in that area and the isolation frequency and relative density of the prevalent fungal genera compared. GenusFusarium was the most prevalent component of the internal seedborne mycoflora in the five locations.Penicillium was prevalent in all locations, taking into account the frequency. However, this genus was predominant only in two locations, when the relative density was considered. The predominantFusarium wasF. moniliforme and the most frequently isolated species ofAlternaria, Aspergillus andPenicillium wereA. alternata, A. flavus andP. decumbens, respectively.Diplodia species were not isolated from any of the samples.

Relationship between Fusarium graminearum and Alternaria alternata contamination and deoxynivalenol occurrence on Argentinian durum wheat

A mycological survey was carried out on durum wheat (Triticum durum) samples from the main production area of Argentina. The isolation frequency and relative density of species of dematiaceous fungi, and genus Fusarium were calculated. Alternaria alternata and Fusarium graminearum were the predominant fungal species. An analysis of deoxynivalenol (DON) natural contamination was also performed on a limited number of samples (60). DON contamination levels in positive samples ranged from 26 to 6400 μg/kg. The non-parametric techniques applied showed that there is a positive relationship between DON contamination and F. graminearum relative densities and a negative relationship between DON contamination and A. alternata relative densities.

Fungi associated with sorghum grain from Argentina

Sorghum (Sorghum bicolor (L.) Moench) is an important cereal produced in and exported from Argentina. The risk of contamination by mycotoxins is related to the mycoflora associated with the sorghum grain. This paper reports on the identification of internal mycoflora of sorghum grain harvested in Argentina in 1991, 1992 and 1993, years with different total rainfall levels.A mycological survey was carried out on sorghum samples, from a location at the humid Argentinian pampa, using a Fusarium/dematiaceous fungi selective medium. The relative density of the prevalent fungal genera were statistically compared. Genus Fusarium was the most prevalent component of the internal seedborne mycoflora in the three harvest seasons. Genera Alternaria, Phoma, Penicillium and Aspergillus were also isolated. The predominant Fusarium was F. moniliforme and the most frequently isolated species of Alternaria, Phoma, Penicillium and Aspergillus were Alt. alternata, Pho. sorghima, Pen. funiculosum and Asp. flavus, respectively. This is the first report of the isolation of Fusarium napiforme in sorghum grain in Argentina.

Deoxynivalenol and contaminant mycoflora in freshly harvested Argentinian wheat in 1993

A mycological survey was carried out on wheat heads from the main production area of Argentina. The isolation frequency and relative density of species from genus Fusarium and dematiaceous fungi were calculated. F graminearum was the predominant Fusarium species; similar to that observed in the USA and Canada. An analysis of deoxynivalenol (DON) natural contamination also was performed on a limited number (44) of samples. DON contamination levels in positive samples ranged from 0.2 to 30 ppm. A stepwise regression procedure showed that, among the species analysed, F. graminearum relative density was related to the DON contamination level and that other prevalent fungi did not influence or modify that relationship.

Study of mathematical models applied to sorption isotherms of Argentinean black bean varieties

Abstract Moisture sorption isotherms of five commercial black bean varieties harvested in the province of Salta, Argentina, were measured. Statistical methodology was applied to compare their sorption characteristics and it was observed that the five varieties could be considered as belonging to a same group. Different equations proposed in the literature were studied and it was found that the best adjustments were provided by the Oswin and the White and Eiring equations. The estimated isotherm equations are given. Adjusting the equations to sorption data found in literature, the White and Eiring equation provided a reasonable adjustment for all of them.

Sorption isotherms of corn—Study of mathematical models

In this paper statistical methodology is used to determine similar groups of Argentine maize varieties and to model the behaviour of the moisture content as a function of the water activity. Different equations proposed in the literature are studied and a common mathematical model is obtained for all varieties whatever the adequacy criteria considered. The use of the goodness of fit criteria is also discussed.

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.

Cyclopiazonic acid and aflatoxins production byAspergillus flavus isolated from Argentinian corn

Thirty-four isolates ofAspergillus flavus obtained from the main Argentinian corn production area were tested for their ability to produce both cyclopiazonic acid (CPA) on corn and on liquid media and aflatoxins on corn.Aflatoxins and CPA were quantified by comparison with standards. The last one was confirmed by mass spectrometry.All but one of the isolates produced CPA on liquid medium in a range between 3120 to 62500 μg/kg, 27/34 isolates produced CPA on corn at levels ranging from 833 to 10000 μg/kg and 5/34 isolates produced aflatoxin B1 in a range between 29 to 115 μg/kg. According to these findings, the percentage ofAspergillus flavus isolates with CPA production ability and their levels of CPA production were higher than the observed elsewhere.It was observed significant differences (p<0,01) between CPA production on corn (median: 1761 μg/Kg) and in liquid medium (median: 27950 μg/Kg). These data represent the first report of the co-production of CPA and aflatoxin B1 by isolates ofAspergillus flavus obtained from corn in Argentina.

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.

Water sorption characteristics of argentine wheat: Statistical methodology

Abstract The aim of this paper is to establish similarities or differences between water sorption characteristics of the most important Argentine wheat varieties and to propose a statistical methodology for their comparison. Ten varieties of wheat were studied by an isopiestic method at 25°C. A balanced two-way analysis of variance with interactions was used. The usual F -tests, assuming normality of the errors, and free-distribution tests were carried out. For the latter test specific software was developed. Transformations were eventually made in order to verify the underlying assumptions of the model. This methodology allows the grouping of 10 varieties according to nonsignificant differences.