Fusarium temperatum and Fusarium subglutinans isolated from maize in Argentina.

Fusarium temperatum and Fusarium subglutinans isolated from the Northwest region (NOA region) of Argentina were characterized using a polyphasic approach based on morphological, biological and molecular markers. Some interfertility between the species was observed. The phylogenetic analysis showed that the two species represented two clades strongly supported by bootstrap values. The toxigenic profile of the strains was also determined. F. temperatum strains were fusaproliferin and beauvericin producers, and only some strains were fumonisin B1 producers. All F. subglutinans strains produced fusaproliferin but none produced beauvericin, indicating a potential toxicological risk from maize harvested in the NOA region of Argentina. This study provides new information about F. temperatum isolated from maize in Argentina.

Toxigenic profile and AFLP variability of Alternaria alternata and Alternaria infectoria occurring on wheat.

The objectives of this study were to evaluate the ability to produce alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TA) by A. alternata and A. infectoria strains recovered from wheat kernels obtained from one of the main production area in Argentina; to confirm using AFLPs molecular markers the identify of the isolates up to species level, and to evaluate the intra and inter-specific genetic diversity of these two Alternaria species. Among all the Alternaria strains tested (254), 84% of them were able to produce mycotoxins. The most frequent profile of toxin production found was the co-production of AOH and AME in both species tested. TA was only produced by strains of A. alternata. Amplified fragment polymorphism (AFLPs) analysis was applied to a set of 89 isolates of Alternaria spp (40 were A. infectoria and 49 were A. alternata) in order to confirm the morphological identification. The results showed that AFLPs are powerful diagnostic tool for differentiating between A. alternata and A. infectoria. Indeed, in the current study the outgroup strains, A. tenuissima was consistently classified. Characteristic polymorphic bands separated these two species regardless of the primer combination used. Related to intraspecific variability, A. alternata and A. infectoria isolates evaluated seemed to form and homogeneous group with a high degree of similarity among the isolates within each species. However, there was more scoreable polymorphism within A. alternata than within A. infectoria isolates. There was a concordance between morphological identification and separation up to species level using molecular markers. Clear polymorphism both within and between species showed that AFLP can be used to asses genetic variation in A. alternata and A. infectoria. The most important finding of the present study was the report on AOH and AME production by A. infectoria strains isolated from wheat kernels in Argentina on a semisynthetic media for the first time. Also, specific bands for A. alternata and A. infectoria have been identified; these may be useful for the design of specific PCR primers in order to differentiate these species and to detect them in cereals.

Toxigenic profile and AFLP variability of Alternaria alternata and Alternaria infectoria occurring on wheat

The objectives of this study were to evaluate the ability to produce alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TA) by A. alternata and A. infectoria strains recovered from wheat kernels obtained from one of the main production area in Argentina; to confirm using AFLPs molecular markers the identify of the isolates up to species level, and to evaluate the intra and inter-specific genetic diversity of these two Alternaria species. Among all the Alternaria strains tested (254), 84% of them were able to produce mycotoxins. The most frequent profile of toxin production found was the co-production of AOH and AME in both species tested. TA was only produced by strains of A. alternata. Amplified fragment polymorphism (AFLPs) analysis was applied to a set of 89 isolates of Alternaria spp (40 were A. infectoria and 49 were A. alternata) in order to confirm the morphological identification. The results showed that AFLPs are powerful diagnostic tool for differentiating between A. alternata and A. infectoria. Indeed, in the current study the outgroup strains, A. tenuissima was consistently classified. Characteristic polymorphic bands separated these two species regardless of the primer combination used. Related to intraspecific variability, A. alternata and A. infectoria isolates evaluated seemed to form and homogeneous group with a high degree of similarity among the isolates within each species. However, there was more scoreable polymorphism within A. alternata than within A. infectoria isolates. There was a concordance between morphological identification and separation up to species level using molecular markers. Clear polymorphism both within and between species showed that AFLP can be used to asses genetic variation in A. alternata and A. infectoria. The most important finding of the present study was the report on AOH and AME production by A. infectoria strains isolated from wheat kernels in Argentina on a semisynthetic media for the first time. Also, specific bands for A. alternata and A. infectoria have been identified; these may be useful for the design of specific PCR primers in order to differentiate these species and to detect them in cereals.

Trichothecene genotypes and chemotypes in Fusarium graminearum strains isolated from wheat in Argentina.

Argentina is the fourth largest exporter of wheat in the world. The main pathogen associated with Fusarium Head Blight (FHB) of wheat in Argentina is Fusarium graminearum lineage 7 also termed F. graminearum sensu stricto in the F. graminearum species complex, which can produce the Type B trichothecenes, usually deoxynivalenol (DON) and its acetylated forms (3-ADON and 15-ADON) or nivalenol (NIV). We used a multiplex PCR assay of Tri3, Tri7, and Tri13 to determine the trichothecene genotype of 116 strains F. graminearum collected from three locations in Argentina and then verified the chemotype by chemical analysis. PCR assays and chemical analyses gave the same results for all strains that produced trichothecenes. Most strains (> 92%) had the 15-ADON genotype, with the remaining strains having the DON/NIV genotype. We observed neither the NIV nor the 3-ADON genotypes amongst the strains evaluated. The nine strains with the DON/NIV genotype produced DON when analyzed chemically. Thus, the Argentinean populations of F. graminearum are similar to those from wheat elsewhere in the world, in that all the strains produced DON/15-ADON and belong to lineage 7. However approximately 8% of the strains tested were incorrectly diagnosed as DON/NIV producers with the current multiplex PCR and were only DON producers by chemical analysis.

Fusarium species (section Liseola) occurrence and natural incidence of beauvericin, fusaproliferin and fumonisins in maize hybrids harvested in Mexico.

Fusarium species can produce fumonisins (FBs), fusaric acid, beauvericin (BEA), fusaproliferin (FUS) and moniliformin. Data on the natural occurrence of FBs have been widely reported, but information on BEA and FUS in maize is limited. The aims of this study were to establish the occurrence of Fusarium species in different maize hybrids in Mexico, to determine the ability of Fusarium spp. isolates to produce BEA, FUS and FBs and their natural occurrence in maize. Twenty-eight samples corresponding to seven different maize hybrids were analyzed for mycobiota and natural mycotoxin contamination by LC. Fusarium verticillioides was the dominant species (44-80%) followed by F. subglutinans (13-37%) and F. proliferatum (2-16%). Beauvericin was detected in three different hybrids with levels ranging from 300 to 400 ng g(-1), while only one hybrid was contaminated with FUS (200 ng g(-1)). All samples were positive for FB1 and FB2 contamination showing levels up to 606 and 277 ng g(-1), respectively. All F. verticillioides isolates were able to produce FB1 (13.8-4,860 µg g(-1)) and some also produced FB2 and FUS. Beauvericin, FUS, FB1 and FB2 were produced by several isolates including F. proliferatum and F. subglutinans and co-production was observed. This is the first report on the co-occurrence of these toxins in maize samples from Mexico. The analysis of the presence of multiple mycotoxins in this substrate is necessary to understand the significance of these compounds in the human and animal food chains.