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White mould ( Sclerotinia sclerotiorum) is a destructive disease of soybean worldwide. However, little is known of its impact on soybean production in Brazil. A meta-analytic approach was used to assess the relationship between disease incidence and soybean yield (35 trials) and between incidence and sclerotia production (29 trials) in experiments conducted in 14 locations across four seasons. Region, site elevation and season included as moderators in random-effects and random-coefficients models did not significantly explain the variability in the slopes of the incidence-yield relationship. The Pearson's r, obtained from back-transforming the Fisher's Z estimated by an overall random-effects model, showed that incidence of white mould was moderately and negatively correlated with yield ( r = −0.76, P < 0.0001). A random-coefficients model estimated a slope of −17.2 kg ha−1%−1, for a mean attainable yield of 3455 kg ha−1, indicating that a 10% increase in white mould incidence would result in a mean yield reduction of 172 kg ha−1. White mould incidence and production of sclerotia were strongly and positively correlated ( r = 0.85, P < 0.0001). For every 10% increase in white mould incidence, 1 kg ha−1 of sclerotia was produced. The relationship between disease incidence and production of sclerotia was stronger in southern regions and at higher elevation. In the absence of management, economic losses associated with white mould epidemics, assuming 43% incidence in 22% of the soybean area, were estimated at approximately US $1.47 billion annually within Brazil. [ABSTRACT FROM AUTHOR]

A large collection ( n = 539) of Fusarium graminearum species complex ( FGSC) isolates was obtained from Brazilian maize, and collections formed according to geography and maize part: (i) kernel ( n = 110) from south and south-central Brazil; (ii) stalk ( n = 134) from Paraná state (south); and (iii) stubble ( n = 295) from Rio Grande do Sul state (south). Species composition, identified using a multilocus genotype approach, was assessed separately in each collection due to differences in geographic sampling. Overall, three species were found: F. meridionale (Fmer; 67% prevalence) with the nivalenol ( NIV) genotype, F. graminearum (Fgra; 19%) with the 15-acetyl (A) deoxynivalenol ( DON) genotype, and F. cortaderiae (Fcor; 14%) with the NIV (49/74) or the 3- ADON (25/74) genotype. In kernels, Fmer was spread across all locations and Fgra and Fcor were found mostly at high elevation (>800 m a.s.l.). The majority (97·8%) of stalk isolates was assigned to Fmer; three were assigned to Fgra. In the stubble, Fmer was less dominant (53%), with a shift towards Fcor as the most frequent species at high elevation sites (>600 m a.s.l.). No differences in the mycelial growth rate were observed among isolates from each species grown at 15°C. Fgra grew faster at 25°C and Fmer showed the widest range of variation across the isolates at both temperatures. The survey data suggest that Fmer may outcompete other species on ears and stalks in comparison to stubble. Additional sampling that controls for other factors, as well as direct testing of aggressiveness on ears and stalk tissue, will be needed to fully evaluate this hypothesis. [ABSTRACT FROM AUTHOR]

Members of the Fusarium graminearum species complex ( FGSC), such as F. graminearum and F. asiaticum, are the main cause of fusarium head blight ( FHB) of wheat and barley worldwide. In this study, 117 FGSC isolates obtained from commercial barley grain produced in Argentina ( n = 43 isolates), Brazil ( n = 35), and Uruguay ( n = 39) were identified to species and trichothecene genotypes, and analysed using amplified fragment length polymorphism ( AFLP) and sequence-related amplified polymorphism ( SRAP) markers. In addition, reductase ( RED) and trichothecene 3- O-acetyltransferase ( Tri101) were sequenced for a subset of 24 isolates. The majority of the isolates ( n = 103) were identified as F. graminearum, which was the only species found in Argentina. In Uruguay, only one F. cortaderiae isolate was found among F. graminearum isolates. In Brazil, F. graminearum also dominated the collection (22/35), followed by F. meridionale (8/35), F. asiaticum (2/35), F. cortaderiae (2/35) and F. austroamericanum (1/35). Species were structured by trichothecene genotype: all F. graminearum were of the 15-acetyldeoxynivalenol ( ADON), F. meridionale, F. asiaticum and F. cortaderiae were of the nivalenol ( NIV), and F. austroamericanum was of the 3- ADON genotype. Both AFLP and SRAP data showed high levels of genetic variability, which was higher within than among countries. Isolates were not structured by country of origin. SRAP analysis grouped F. graminearum in a separate cluster from the other species within the complex. However, AFLP analysis failed to resolve the species into distinct clades with partial clustering of F. meridionale, F. austroamericanum, F. asiaticum and F. graminearum isolates. [ABSTRACT FROM AUTHOR]

Aims: Evaluate the in vitro effect of imidazolium salts (IMS) on the conidia germination and mycelial growth of Fusarium graminearum and their in vivo efficacy for suppressing the symptoms of the disease and infection of kernels in wheat plants., Methods and Results: The minimum inhibitory concentrations (MIC) of three IMS (C16 MImCl, C16 MImMeS and C16 MImNTf2 ) were determined for four F. graminearum isolates using serial broth dilution method. The MICs found for all IMS were either 3·12 or 6·25 μg ml(-1) across the isolates, with the former as the most frequent. In the mycelial growth assay on potato dextrose agar media, only the C16 MImCl among the IMS reduced 50% of mycelial growth of one isolate at an estimated concentration of 0·32 mg ml(-1) . The time-kill curves showed a strong fungicidal effect starting 1 h after incubation at a concentration of 12·5 μg ml(-1) , representing a fourfold increase in the most frequent MIC. The C16 MImCl sprayed onto the spikes of potted wheat plants during the flowering stage reduced disease intensity at levels comparable to the commercial fungicide when applied preventatively (1 h prior to fungal inoculation), rather than curatively, and at the higher dosage (2 mg ml(-1) ) rather than lower dosage (0·5 mg ml(-1) )., Conclusions: C16 MImCl proved to be a potent inhibitor of F. graminearum growth and provided good levels of control of the disease at levels comparable to a commercial fungicide, in wheat plants treated prior to fungal infection during flowering stages., Significance and Impact of the Study: This study suggests the potential of using IMS as alternative to the hazardous standard fungicides in the management of Fusarium head blight of wheat., (© 2016 The Society for Applied Microbiology.)

Ear rots caused by Fusarium spp. are among the main fungal diseases that contribute to poor quality and the contamination of maize grains with mycotoxins. This study aimed to determine the visual incidence of fungal-damaged kernels (FDKs), the incidence of two main Gibberella (a teleomorph of Fusarium) complexes (G. fujikuroi and G. zeae) associated with maize using a seed health blotter test, and the fumonisin levels, using high performance liquid chromatography, in samples of maize grains grown across 23 municipalities during the 2008/09 and 2009/10 growing seasons. Additionally, 104 strains that were representative of all of the analysed samples were identified to species using PCR assays. The mean FDK was seven per cent, and only six of the samples had levels greater than six per cent. Fusarium spp. of the G. fujikuroi complex were present in 96% of the samples, and G. zeae was present in 18% of the samples (5/27). The mean incidence of G. fujikuroi was 58%, and the incidence of G. zeae varied from 2 to 6%. FB1 was found in 58.6%, FB2 in 37.9%, and both toxins in 37.9% of the samples. The FB1 and FB2 levels were below the quantification limits for 41.3% of the samples, and the mean FB1 levels (0.66 μg/g) were higher than the mean FB2 levels (0.42 μg/g). The PCR identification separated the 104 isolates into three of the G. fujikuroi complex: F. verticillioides (76%), F. subglutinans (4%) and F. proliferatum (2%); and G. zeae (anamorph = F. graminearum) (18%). Our results confirmed the dominance of F. verticillioides, similar to other regions of Brazil, but they differed due to the relatively higher incidence of F. graminearum. Total fumonisin levels were below the maximum limit determined by current Brazilian regulations.

Fusarium head blight is a disease of primary concern to small-grain cereals of Brazil, including barley. Its main causal agent, Fusarium graminearum species complex (Fg complex)¸ is able to produce mycotoxins, especially deoxynivalenol (DON) and nivalenol (NIV), that usually contaminate grain. Strains that produce DON may also produce its acetylated derivatives: 3-acetyl-DON (3-ADON) and 15-acetyl-DON (15-ADON). Ninety two isolates were obtained from samplings of barley grain during three years (2007, 2008 and 2009) from several fields in both southern and northern production regions of Rio Grande do Sul state, Brazil. These isolates were examined for polymerase chain-reaction-based (PCR) trichothecene genotype based on the amplification of portions of Tri3 and Tri12. There was no effect of year or region on the proportion of trichothecene genotypes. Overall, 66% of the strains (61/92) were 15-ADON, 4.4% (4/92) were 3-ADON and 29.3% (27/92) were NIV. The overall NIV/DON ratio estimated (0.41) was five times higher than that found in previous studies with strains from wheat grown in the same region. Species identification of nine strains representing the trichothecene genotypes, based on comparisons of DNA sequences of portions of the PHO, RED and URA genes with sequences from curated reference isolates of Fusarium from GenBank, revealed that they belong to F. graminearum sensu stricto (four 15-ADON and one 3-ADON strain), F. meridionale (three NIV strains) and F. austroamericanum (one 3-ADON strain). These results add to the current regional knowledge of trichothecene genotypes and species within the Fg complex affecting barley in the region., (Copyright © 2011 Elsevier B.V. All rights reserved.)