Characterization and genetic variability of feed-borne and clinical animal/human Aspergillus fumigatus strains using molecular markers.

Aspergillus fumigatus, the major etiological agent of human and animal aspergillosis, is a toxigenic fungus largely regarded as a single species by macroscopic and microscopic features. However, molecular studies have demonstrated that several morphologically identified A. fumigatus strains might be genetically distinct. This work was aimed to apply PCR-restriction length fragment polymorphisms (PCR-RFLP) and random amplification of polymorphic DNA (RAPD) molecular markers to characterize a set of feed-borne and clinical A. fumigatus sensu lato strains isolated from Argentina and Brazil and to determine and compare their genetic variability. All A. fumigatus strains had the same band profile and those typical of A. fumigatus sensu stricto positive controls by PCR-RFLP. Moreover, all Argentinian and Brazilian strains typified by RAPD showed similar band patterns to each other and to A. fumigatus sensu stricto reference strains regardless of their isolation source (animal feeds or human/animal clinical cases) and geographic origin. Genetic similarity coefficients ranged from 0.61 to 1.00, but almost all isolates showed 78% of genetic similarly suggesting that genetic variability was found at intraspecific level. Finally, benA sequencing confirmed its identification as A. fumigatus sensu stricto species. These results suggest that A. fumigatus sensu stricto is a predominant species into Aspergillus section Fumigati found in animal environments as well as in human/animal clinical cases, while other species may be rarely isolated. The strains involved in human and animal aspergillosis could come from the environment where this fungus is frequently found. Rural workers and animals would be constantly exposed.

Factors affecting distribution and abundance of Aspergillus section Nigri in vineyard soils from grapevine growing regions of Argentina.

BACKGROUND: Aspergillus species belonging to section Nigri are the main fungi responsible for ochratoxin (OTA) contamination in grapes and wine. These species live as saprophytes in the superficial layer of the vineyard soil. We evaluated the biodiversity of potentially ochratoxigenic strains of Aspergillus section Nigri isolated from vineyard soils from different grapevine growing regions of Argentina. The isolates were characterized by classical and molecular methods. A multiple correspondence analysis was performed to identify the overall correlation of the Aspergillus group distribution with environmental conditions, geographical characteristics and vineyard practices. RESULTS: Aspergillus niger aggregate was the prevalent group (71%) and A. carbonarius made up only 2%. Species discrimination by species-specific primers showed that in A. niger aggregate 89% were A. tubingensis; 97% of the uniseriate were A. japonicus/A. aculeatus. Isolates belonging to these groups were unable to produce OTA. Our results clearly demonstrate a strong association between presence of A. carbonarius, high average temperatures and drip irrigation. Precipitation levels appear as a secondary factor, and altitude, vineyard age, predominant species, grape variety or total fungal count showed no association with A. carbonarius. CONCLUSION: We demonstrated a low prevalence of ochratoxigenic species in vineyard soil from the grape-growing regions of Argentina.

Occurrence of deoxynivalenol and deoxynivalenol-3-glucoside in durum wheat from Argentina.

The occurrence of deoxynivalenol, 3- and 15-deoxynivalenol and deoxynivalenol-3-glucoside in 84 durum wheat samples, from the Argentinean main growing area, was investigated during 2012/13 and 2013/14 using LC-MS/MS. Deoxynivalenol was found in all samples at concentrations varying between

Impact of water potential on growth and germination of Fusarium solani soilborne pathogen of peanut.

Studies were conducted to determine the effect of osmotic and matric stress on germination and growth of two Fusarium solani strains, the etiological agent responsible of peanut brown root rot. Both strains had similar osmotic and matric potential ranges that allowed growth, being the latter one narrower. F. solani showed the ability to grow down to -14 MPa at 25 °C in non-ionic modified osmotic medium, while under matric stress this was limited to -8.4 MPa at 25 °C. However, both strains were seen to respond differently to decreasing osmotic and matric potentials, during early stages of germination. One strain (RC 338) showed to be more sensitive to matric than osmotic (non ionic) and the other one (RC 386) showed to be more sensitive to osmotic than matric imposed water stress. After 24 h of incubation, both isolates behaved similarly. The minimum water potential for germination was -8.4 MPa on glycerol amended media and -5.6 MPa for NaCl and PEG amended media, respectively. The knowledge of the water potential range which allow mycelia growth and spore germination of F. solani provides an inside to the likely behaviour of this devastating soilborne plant pathogen in nature and has important practical implications.

Occurrence of Fusarium spp. and fumonisin in durum wheat grains.

A survey was carried out to determine Fusarium species and fumonisin contamination in 55 durum wheat (Triticum turgidum L. var. durum) samples collected during two harvest seasons (2007 and 2008) using HPLC and further LC-MS/MS confirmation. All samples showed Fusarium contamination with infection levels ranging from 8 to 66%, F. proliferatum being the species most frequently isolated during 2007 and the second most frequently isolated one during the 2008 harvest season, respectively. Natural contamination with fumonisins was found in both harvest seasons. In 2007, 97% of the samples showed total fumonisin (FB(1) + FB(2)) levels ranging from 10.5 to 1245.7 ng/g, while very low levels of fumonisins were detected in samples collected during 2008. These results could be explained by differences in the amount of rainfall during both periods evaluated. A selected number (n = 48) of F. proliferatum isolates showed fumonisin production capability on autoclaved rice. This is the first report of the presence of natural fumonisins in durum wheat grains.

Impact of water potential on growth and germination of Fusarium solani soilborne pathogen of peanut

Studies were conducted to determine the effect of osmotic and matric stress on germination and growth of two Fusarium solani strains, the etiological agent responsible of peanut brown root rot. Both strains had similar osmotic and matric potential ranges that allowed growth, being the latter one narrower. F. solani showed the ability to grow down to -14 MPa at 25 °C in non-ionic modified osmotic medium, while under matric stress this was limited to -8.4 MPa at 25 °C. However, both strains were seen to respond differently to decreasing osmotic and matric potentials, during early stages of germination. One strain (RC 338) showed to be more sensitive to matric than osmotic (non ionic) and the other one (RC 386) showed to be more sensitive to osmotic than matric imposed water stress. After 24 h of incubation, both isolates behaved similarly. The minimum water potential for germination was -8.4 MPa on glycerol amended media and -5.6 MPa for NaCl and PEG amended media, respectively. The knowledge of the water potential range which allow mycelia growth and spore germination of F. solani provides an inside to the likely behaviour of this devastating soilborne plant pathogen in nature and has important practical implications.

Fusaproliferin, beauvericin and fumonisin production by different mating populations among the Gibberella fujikuroi complex isolated from maize.

The production of fumonisins, fusaproliferin and beauvericin by Gibberella fujikuroi different mating populations isolated from maize in Argentina was evaluated. From 203 strains of Fusarium verticillioides (G. fujikuroi mating population A), 193 were fumonisin producers. Among members of mating population A, female fertile strains produced 20% more toxin than female sterile ones. Among 78 Fusarium proliferatum strains (G. fujikuroi mating population D) 65 produced fumonisins. The percentage of strains that were high, intermediate and low level toxin producers varied according to the species evaluated and the area from which the strains were isolated. Fusarium subglutinans (G. fujikuroi mating population E) strains produced low levels or were no fumonisin producers. Strains from both G. fujikuroi mating populations D and E were able to produce fusaproliferin and beauvericin. Among the members of F. subglutinans (G. fujikuroi mating population E) the fusaproliferin production was more constant. Co-production of fumonisin, fusaproliferin and beauvericin among the strains belonging to G. fujikuroi D and E was also observed. The co-production of fumonisin, beauvericin and fusaproliferin in maize need to be considered, since from the toxicological point of view interactions between these toxins could occur. The toxigenic ability of the strains evaluated prompt us that is necessary to determine the natural occurrence of fusaproliferin and beauvericin in Argentinean maize.