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Fusarium poae is one of the Fusarium species commonly detected in wheat kernels affected by Fusarium Head Blight. Fusarium poae produces a wide range of mycotoxins including nivalenol (NIV). The effect of temperature on colony growth and NIV production was investigated in vitro at 5–40 °C with 5 °C intervals. When the data were fit to a Beta equation (R 2  ≥ 0.97), the optimal temperature was estimated to be 24.7 °C for colony growth and 27.5 °C for NIV production. The effects of temperature on infection incidence, fungal biomass, and NIV contamination were investigated by inoculating potted durum wheat plants at full anthesis; inoculated heads were kept at 10–40 °C with 5 °C intervals for 3 days and then at ambient temperature until ripening. Temperature significantly affected the incidence of floret infection and fungal biomass (as indicated by DNA amount) in the affected heads but did not affect NIV content in the head tissue. Inoculation of potted plants with F. poae did not reduce yield. [ABSTRACT FROM AUTHOR]

Abstract Fusarium head blight (FHB) is a destructive disease of small grain cereals with Fusarium graminearum as one of the most important causal agents. FHB not only can reduce yield and quality of grains, but also lead to accumulation of mycotoxins in grain, thereby threatening human and animal health. In this study, we observed that epoxiconazole exhibits strong inhibitory effects on both carbendazim-resistant and phenamacril-resistant isolates using mycelial growth inhibition assays. The artificially inoculated field trials further showed that epoxiconazole increased the control efficacy of FHB by being able to control carbendazim-resistant and phenamacril-resistant isolates. Epoxiconazole triggered DON production and Tri5 expression in vitro. However, in addition to increased FHB control efficacy and grain yield, decreased DON levels were measured in field trials after epoxiconazole applications. FHB control, grain yields and DON levels were significantly correlated with each other, suggesting that the visual disease rating can be used as an indicator of grain yields and mycotoxin contamination. Meanwhile, the frequency of carbendazim-resistant alleles in F. graminearum populations was dramatically reduced after epoxiconazole applications. In addition, epoxiconazole seed treatments had no effect on seed germination but phytotoxicity was apparent through growth inhibition of wheat seedlings. Overall, these findings of this study provide useful information for wheat protection programs against toxigenic fungi responsible for FHB and the consequent mycotoxin accumulation in grains. Graphical Abstract Unlabelled Image Highlights • Epoxiconazole exhibits strong activity and can be used to manage fungicide resistance in F. graminearum. • Epoxiconazole has a phytotoxic effect to wheat as seed treatment. • Epoxiconazole exhibits increased FHB control and grain yield and decreased mycotoxin levels. • FHB control, grain yield and mycotoxin levels affected by epoxiconazole were significantly correlated. • Epoxiconazole exhibits a greening effect during the late period of wheat. [ABSTRACT FROM AUTHOR]

The selection for Fusarium head blight (FHB) resistance is a bit difficult in breeding programs due to the complex inheritance of the resistance genes and the climatic effect on disease vigorous and expression. The present study was performed to assess microsatellite markers related to the resistance against FHB and examine the efficiency of these microsatellite markers while choosing for the resistance genes in all populations derived from a resistant parent. Both recombinant inbred lines (RIL) of Annong1124 (02P67/Aizao87//Yangmai158) and segregating lines of Zhoumai–27 × Shengxuani–6 were evaluated for their resistance to FHB by inoculating with Fusarium graminearum in the greenhouse as well as in the field. A total of 19 and 15 microsatellite markers from the chromosomes 3BS and 5A, respectively, were applied to RIL and each population of Zhoumai–27 (F 2 , F 3 ). On the other hand, seven microsatellite markers from chromosomes 4B were applied to F 2 and F 3 segregating populations but there was a general lack of marker polymorphism on 4B for the employed parents of RIL. The most significant SSR markers were detected on the chromosome 3B and 5A explaining 7.30% and 21.74% of phenotypic variation, respectively, for the resistance in the RIL. The best quantitative trait loci (QTL) were detected on 4B for F 2 and F 3 populations with marker interval of WMC238-GWM66 with the LOD score 40.49 and 41.52, respectively. The phenotypic variations for F 2 and F 3 on chromosome 5A were detected with the account of 0.49 and 2.33 (BARC197-GWM179), respectively. The additive effects on chromosomes 3BS, 4B, and 5A were clearly higher in F3 population as compared to the F 2 population. SSR markers on the chromosome 3BS in addition to SSR markers on 4B and 5A have the potential for improving the wheat cultivars with improved FHB resistance through the use of marker-assisted selection. [ABSTRACT FROM AUTHOR]

Combining the biological control agent Cryptococcus flavescens OH 182.9 (NRRL Y-30216) with a triazole fungicide has potential for significantly reducing Fusarium head blight (FHB) but is complicated by yeast sensitivity to the chemical. Protracted exposure of strain OH 182.9 to increasing concentrations of prothioconazole (PTC) during growth in liquid culture resulted in stable variants with doubling times of 135–174 min in the presence of 50 ppm prothioconazole compared to 228 min for the progenitor strain. Prothioconazole-tolerant (PTCT) variants were confirmed to be cospecific with the progenitor strain using Biolog™ YT Microplate™ and phylogenetic analysis. In greenhouse tests, PTCT variant OH 182.9 4C reduced head blight severity by 83% compared to 36% for the wild type strain ( P ⩽ 0.05, Bonferroni mean separation). Disease reductions incited by other variants were not significant. Four PTCT variants, PTC applied as Proline® at label rate, and combinations of PTCT variants and fungicide significantly reduced FHB severity and incidence ( P ⩽ 0.05). In two field trials on susceptible winter wheat, OH 182.9 3C and OH 182.9 4C reduced severity by 34% and 42%, respectively, compared to the control ( P ⩽ 0.05) in one trial and 21% and 24%, respectively, in the other (not significantly different at P ⩽ 0.05). In comparison, strain OH 182.9 did not reduce FHB severity consistently. For both field trials on two wheat varieties, treating flowering wheat heads with PTC and a PTCT variant resulted in the greatest numerical reduction of FHB severity, incidence, and DON relative to other treatments. However, combining PTCT variants with PTC did not significantly enhance treatment efficacy vs PTC alone. [ABSTRACT FROM AUTHOR]

To better understand the contribution of the quantitative fusarium head blight (FHB) resistance locus, 2DL QTL from Wuhan-1, we have characterized two pairs of sister lines carrying either the 2DL QTL or no known QTLs. In wheat spikes, our visual and microscopic observations suggested that the 2DL QTL suppress fungal infection in inoculated spikelets and reduce spread from spikelets to rachis. Transcriptome profiling of infected spikelets showed changes in expression for 487 probe sets between the 2DL-carrying and the null lines. Of 27 transcripts selected for validation, eight candidate genes with similar expression profiles between the two pair of lines were identified. [ABSTRACT FROM AUTHOR]

Because of the health risks associated with the ingestion of the mycotoxin deoxynivalenol (DON) produced by Fusarium head blight (FHB), improving its detection in wheat kernels is a major research goal. Currently, assessments are largely performed visually by human experts. Being subjective, such assessments may not always be consistent or entirely reliable. As a result, methods with a higher degree of objectivity have been investigated, and special attention has been dedicated to the use of hyperspectral imaging (HSI) as the basis for more reliable detection strategies. This paper presents an algorithm for automatic detection of FHB in wheat kernels using HSI. The goal was to develop a simple and accurate algorithm which gave as output an index that can be interpreted as the likelihood of the kernel being infected by FHB. With a classification accuracy above 91%, the developed algorithm was robust to factors such as shape, orientation, shadowing and clustering of kernels. It was shown that the algorithm was not only suitable for detecting FHB, but it also has the capability, albeit limited, of estimating DON concentrations in wheat kernels. [ABSTRACT FROM AUTHOR]

A comparison between two VIS–NIR spectral based systems performed in laboratory vs. in-field for the early detection of Fusarium head blight infection in two cultivars of durum wheat (Creso and Simeto) was carried out. The VIS–NIR spectrophotometric data were analysed with multivariate statistical tools. For both, laboratory and in-field experiments two analytical conditions were tested for two cultivars: diseased plants (artificial infection without fungicide treatment) and healthy plants (treatment with Folicur SE). Spectral measurements were performed at the different sampling times 6, 8, 12 and 15 d after artificial infection which correspond to the following Zadoks'' scale growth stages: GS70, GS71, GS73 and GS75. The infection visible onset (VO) was then evaluated by an expert at the soft dough growth stage GS85. Since the growth stages revealed a great influence on spectral reflectance data, separated PLSDA models were adopted to differentiate diseased and healthy plants at the different sampling times. Using the Euclidean distance matrix cladogram results for the laboratory, three models were used considering spectral data from GS70, GS71 + GS73, GS75, while for in-field data from GS70 + GS71 and GS73 + GS75. In the laboratory good performance of classification (86%) was observed at GS71 + GS73 i.e., only 8–10 days after the infection. The in-field measurement showed a lower percentage of correct classification at the same growth stages. Finally the VIS–NIR spectral analysis could facilitate detection of Fusarium disease anticipating visual assessment. [Copyright &y& Elsevier]

Abstract: Certain Fusarium species cause head blight of wheat and other small grains worldwide and produce trichothecene mycotoxins. These mycotoxins can induce toxicoses in animals and humans and can contribute to the ability of some fusaria to cause plant disease. Production of the trichothecene 3-acetyldeoxynivalenol (3-ADON) versus 15-acetyldeoxynivalenol (15-ADON) is an important phenotypic difference within and among some Fusarium species. However, until now, the genetic basis for this difference in chemotype has not been identified. Here, we identified consistent DNA sequence differences in the coding region of the trichothecene biosynthetic gene TRI8 in 3-ADON and 15-ADON strains. Functional analyses of the TRI8 enzyme (Tri8) in F. graminearum, the predominant cause of wheat head blight in North America and Europe, revealed that Tri8 from 3-ADON strains catalyzes deacetylation of the trichothecene biosynthetic intermediate 3,15-diacetyldeoxynivalenol at carbon 15 to yield 3-ADON, whereas Tri8 from 15-ADON strains catalyzes deacetylation of 3,15-diacetyldeoxynivalenol at carbon 3 to yield 15-ADON. Fusarium strains that produce the trichothecene nivalenol have a Tri8 that functions like that in 15-ADON strains. TRI3, which encodes a trichothecene carbon 15 acetyltransferase, was found to be functional in all three chemotypes. Together, our data indicate that differential activity of Tri8 determines the 3-ADON and 15-ADON chemotypes in Fusarium. [Copyright &y& Elsevier]

Fusarium graminearum, Fusarium culmorum and Fusarium cerealis are major causal agents of Fusarium Head Blight (scab) which is a disease of global significance in all cereal growing areas. These fungi produce trichothecene mycotoxins, principally nivalenol (NIV) and deoxynivalenol (DON). Genes Tri13 and Tri7 from the trichothecene biosynthetic gene cluster convert DON to NIV (Tri13) and NIV to 4-acetyl-NIV (Tri7). We have developed positive–negative PCR assays based on these two genes, which accurately indicate a DON or NIV chemotype in F. graminearum, F. culmorum and F. cerealis. These assays are useful in assessing the risk of trichothecene contamination, and can be informative in epidemiological studies. All NIV chemotype isolates studied have functional copies of both Tri13 and Tri7, and all DON-producing isolates have both genes disrupted or deleted. We have identified several mutations in these genes, which are conserved across F. graminearum lineage, RAPD and SCAR groupings and between the three species. There appears to be evidence of inter-species hybridisation within the trichothecene biosynthetic gene cluster. [Copyright &y& Elsevier]

Abstract The Fusarium graminearum species complex (FGSC), the causal agents of Fusarium head blight (FHB) in wheat, has the different geographically distributed species. Our previous study suggested that a DMI fungicide metconazole exhibits a strong fungicidal activity in mycelial growth of Chinese FHB pathogens and metconazole is currently a most effective compound of commercial fungicides for controlling FHB in China. In the current study, metconazole-resistant F. graminearum mutants were induced by chemical taming and their molecular and biological characteristics were determined. Compared to the corresponding parental strains, three mutation genotypes (two single mutations G443S and D243N, and a combined mutation E103Q&V157 L) were observed in the FgCYP51A of metconazole-resistant mutants. In addition to FgCYP51A mutation, all the mutants had no change on sequences of FgCYP51B and FgCYP51C and promotor sequences of FgCYP51 s, but expression patterns of FgCYP51 s were different. Compared to the corresponding parental strains, overexpression of FgCYP51A , FgCYP51B and FgCYP51C was observed in the mutant conferring D243N mutation, overexpression of FgCYP51A and FgCYP51B was observed in the mutant conferring E103Q&V157L mutations, and overexpression of FgCYP51A was observed in the mutant conferring G443S mutation. Biological fitness of the mutants conferring D243N mutation or E103Q&V157 L mutations significantly decreased in comparison to the corresponding parental strains, suggesting a fitness penalty. The mutants conferring G443S mutation had no change in biological fitness as compared with the parental strain, indicating that the G443S mutation may emerge in field resistant populations of F. graminearum in the future. In addition, a positive cross resistance between metconazole and other tested DMI fungicides was observed in the mutants conferring D243N mutation or E103Q&V157L mutations, but no cross resistance between metconazole and ipconazole or prochloraz was observed in the mutants conferring G443S mutation. Therefore, we concluded that the mutation genotype of FgCYP51A may cause the differences of biological fitness, cross-resistance and FgCYP51 s overexpression patterns. Such information will increase our understanding of resistance mechanism of F. graminearum to DMIs and could provide new reference data for the management of FHB. Graphical abstract Unlabelled Image Highlights • Three mutation genotypes of CYP51A were first reported in F. graminearum. • The mutants conferring D243N or E103Q&V157 L suffered a fitness penalty. • The mutants conferring G443S had no fitness penalty, showing a high resistant risk. • Cross resistance patterns differ in the mutants conferring different genotype. • Over expression of CYP51s differ in the mutants conferring different genotype. [ABSTRACT FROM AUTHOR]

Bacillus thuringiensis israelensis biological larvicides represent a good approach to support vector borne diseases control programs targeting earlier aquatic larval stages to limit their adult mosquito spreading. BUPM98, a Tunisian B. thuringiensis israelensis strain, is highly active against Aedes aegypti larvae. For the production of BUPM98 bioinsecticide, an agricultural by-product medium consisting of gruel and soybean meal has been optimized. Optimization of the medium composition was performed with statistical methodology based on experimental designs. Accordingly, the optimum toxin production was 2375.36 ± 48.52 mg/L at the following conditions: K 2 HPO 4 : 60 mM, pH: 7.6 and soybean meal: 32 g/L, which led to an improvement of 30% compared to the starting conditions. The impact of water quality on the effectiveness of BUPM98 delta-endotoxins against Culex pipiens larvae was investigated. Indeed, under field conditions, the direct application of BUPM98 fermentation product in stagnant water pools reduced the immature density of C. pipiens larvae by more than 95% after 48 h of treatment. Prolonged residual action was observed until 14 days. In conclusion, BUPM98, a local strain of B. thuringiensis israelensis , is very promising bioinsecticide for mosquito population management in Tunisia. [ABSTRACT FROM AUTHOR]

Surveys for crown rot (FCR) and head blight (FHB) of Algerian wheat conducted during 2014 and 2015 revealed that Fusarium culmorum strains producing 3-acetyl-deoxynivalenol (3ADON) or nivalenol (NIV) were the causal agents of these important diseases. Morphological identification of the isolates ( n FCR = 110, n FHB = 30) was confirmed by sequencing a portion of TEF1 . To assess mating type idiomorph, trichothecene chemotype potential and global population structure, the Algerian strains were compared with preliminary sample of F. culmorum from Italy ( n = 27), Australia ( n = 30) and the United States ( n = 28). A PCR assay for MAT idiomorph revealed that MAT1-1 and MAT1-2 strains were segregating in nearly equal proportions, except within Algeria where two-thirds of the strains were MAT1-2 . An allele-specific PCR assay indicated that the 3ADON trichothecene genotype was predominant globally (83.8% 3ADON) and in each of the four countries sampled. In vitro toxin analyses confirmed trichothecene genotype PCR data and demonstrated that most of the strains tested (77%) produced culmorin. Global population genetic structure of 191 strains was assessed using nine microsatellite markers (SSRs). AMOVA of the clone corrected data indicated that 89% of the variation was within populations. Bayesian analysis of the SSR data identified two globally distributed, sympatric populations within which both trichothecene chemotypes and mating types were represented. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) mainly caused by Fusarium graminearum is a devastating disease that causes extensive yield and quality losses to wheat in humid and semi-humid regions of the world. The biocontrol effect of two bacterial strains on FHB incidence, severity and deoxynivalenol (DON) accumulation in wheat was evaluated in field trials during 2010 and 2011 at Marcos Juarez, Córdoba province, Argentina. Bacillus subtilis RC 218 and Brevibacillus sp. RC 263 applied at anthesis period were evaluated through several combinations of cell type, strains, inoculum density (10 4 and 10 6 cfu/ml) and physiological modification. A significant and consistent biocontrol effect on FHB severity and DON contamination was observed in all the evaluated treatments during both 2010 and 2011 field trials. Reduction in FHB severity ranged 62–76% and 42–58% for 2010 and 2011 field trials, respectively. When evaluating the effect of the combined strains (10 4 + 10 4 and 10 6 + 10 6 cfu/ml), a better biocontrol effect was observed in 2010 field trial. After biocontrol treatments, no DON accumulation was observed in wheat heads; meanwhile in control plots an average of 1372 μg/kg DON was detected during the two trials. FHB incidence was significantly reduced by biocontrol treatments during the 2010 field trial but not during the 2011 field trial. The results showed the effectiveness of the two formulated biological control agents in reducing both FHB severity and DON accumulation by F. graminearum under semi controlled field conditions. [ABSTRACT FROM AUTHOR]

Fusarium graminearum sensu stricto causes Fusarium head blight (FHB) in wheat and barley, and contaminates grains with several trichothecene mycotoxins, causing destructive yield losses and economic impact in the United States. Recently, a F. graminearum strain collected from Minnesota (MN) was determined to produce a novel trichothecene toxin, called NX-2. In order to determine the spatial and temporal dynamics of NX-2 producing strains in MN, North Dakota (ND) and South Dakota (SD), a total of 463 F. graminearum strains were collected from three sampling periods, 1999–2000, 2006–2007 and 2011–2013. A PCR-RFLP based diagnostic test was developed and validated for NX-2 producing strains based on polymorphisms in the Tri1 gene. Trichothecene biosynthesis gene ( Tri gene )-based polymerase chain reaction (PCR) assays and ten PCR-restriction fragment length polymorphism (RFLP) markers were used to genotype all strains. NX-2 strains were detected in each sampling period but with a very low overall frequency (2.8%) and were mainly collected near the borders of MN, ND and SD. Strains with the 3ADON chemotype were relatively infrequent in 1999–2000 (4.5%) but increased to 29.4% in 2006–2007 and 17.2% in 2011–2013. The distribution of 3ADON producing strains also expanded from a few border counties between ND and MN in 1999–2000, southward toward the border between SD and MN in 2006–2007 and westward in 2011–2013. Genetic differentiation between 2006–2007 and 2011–2013 populations (3%) was much lower than that between 1999–2000 and 2006–2007 (22%) or 1999–2000 and 2011–2013 (20%) suggesting that most change to population genetic structure of F. graminearum occurred between 1999–2000 and 2006–2007. This change was associated with the emergence of a new population consisting largely of individuals with a 3ADON chemotype. A Bayesian clustering analysis suggested that NX-2 chemotype strains are part of a previously described Upper Midwestern population. However, these analyses also suggest that the NX-2 isolates could represent a distinct population, but that interpretations of population assignment are influenced by the small number of NX-2 strains available for analysis. [ABSTRACT FROM AUTHOR]

The effect of phytohormones on the defense response of wheat against Fusarium graminearum infection was investigated. Infection of heads with F. graminearum induced accumulation of salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA), and indole acetic acid (IAA). Exogenous phytohormone treatments showed crosstalk between them and a complex effect on expression of the genes ATB2 , ExpB6 , LEA Td16 , PR1 , Pdf1.2 , PR4 . JA treatment reduced F. graminearum growth and fusarium head blight (FHB) symptoms while an increase in FHB was observed with ABA. Transient down-regulation of allene oxide synthase ( AOS ) supports a complex role for JA in wheat head. [ABSTRACT FROM AUTHOR]

Abstract: The complete genome of the biocontrol antagonist Bacillus amyloliquefaciens AS 43.3 is reported. B. amyloliquefaciens AS 43.3 has previously been shown to be effective in reducing Fusarium head blight in wheat. The 3.9Mbp genome was sequenced, assembled, and annotated. Genomic analysis of the strain identified 9 biosynthetic gene clusters encoding secondary metabolites associated with biocontrol activity. The analysis identified five non-ribosomal peptide synthetase clusters encoding three lipopeptides (surfactin, iturin, and fengycin), a siderophore (bacillibactin), and the antibiotic dipeptide bacilysin. In addition, three polyketide synthetase clusters were identified which encoded for the antibacterials: bacillaene, difficidin, and macrolactin. In addition to the non-ribosomal mediated biosynthetic clusters discovered, we identified a ribosomally encoded biosynthetic cluster that produces the antibiotic plantazolicin. To confirm the gene clusters were functional, cell-free culture supernatant was analyzed using LC–MS/MS. The technique confirmed the presence of all nine metabolites or their derivatives. The study suggests the strain is most likely a member of the B. amyloliquefaciens subsp. plantarium clade. Comparative genomics of eight completed genomes of B. amyloliquefaciens identify the core and pan-genomes for the species, including identifying genes unique to the biocontrol strains. This study demonstrates the growing importance of applying genomic-based studies to biocontrol organisms of plant pathogens which can enable the rapid identification of bioactive metabolites produced by a prospective biological control organism. In addition, this work provides a foundation for a mechanistic understanding of the B. amyloliquefaciens AS 43.3/Fusarium head blight biocontrol interaction. [Copyright &y& Elsevier]

Graphical abstract Highlights • Dead biocontrol agent cells support growth of Fusarium graminearum in liquid culture. • Bipolar conidial germination and hyphal branching stimulated by dead antagonist cells. • Dead cells reduced live cell inhibition of bipolar conidial germination and branching. • Dead cells increased FHB severity, incidence and DON content of wheat grain. • Dead cells nullified disease reduction trend seen when treating with live cells alone. Abstract Microbially-based plant disease control products have achieved commercial market success, but the efficacy of biocontrol products is sometimes deemed inconsistent. Declines in product viability before or after application results in a mixture of non-viable and viable antagonist cells being present on infection courts. We hypothesized that these non-viable cells could provide a nutritive benefit to plant pathogen propagules and thereby reduce the efficacy and consistency of performance of a biocontrol product. We tested this hypothesis on the pathogen Fusarium graminearum , an important causal agent of Fusarium head blight (FHB) of wheat, and a yeast antagonist Papiliotrema flavescens (formerly Cryptococcus flavescens) strain OH 182.9 3C. When F. graminearum was grown in a liquid basal salts medium without carbon or nitrogen but supplemented with increasing levels of non-viable cells of strain OH 182.9 3C, the amount of pathogen biomass produced increased (P ≤ 0.05) with each sequentially higher level of non-viable cell amendment tested. Total conidial germination of F. graminearum on membranes was initially greatest in the control and least when conidia were combined with live cells of antagonist OH 182.9 3C. Though the presence of dead cells initially resulted in reduced conidial germination, the treatment increased bipolar germination of conidia after 6 h compared to the control (89% and 45%, respectively) (P ≤ 0.05, FPLSD). Treatment with a combination of dead and live cells supported more bipolar germination than live cells alone (51% and 29%, respectively). After 12 h, dead cells had a similar stimulating effect on the branching of germ tubes and negated the reduction in branching seen when treating with live cells alone. Scanning electron microscopy indicated that the presence of non-viable cells of P. flavescens OH 182.9 3C modified the ectotrophic growth of F. graminearum on wheat lemma tissues. In greenhouse experiments, live cells of P. flavescens tended to reduce FHB incidence, severity and the deoxynivalenol content of spring wheat grain compared to the control but treatment with live cells amended with dead cells increased all of these disease parameters compared to the live cells only treatment (P ≤ 0.05, FPLSD). Results indicate that non-viable antagonist cells present in a biocontrol cell treatment can reduce disease control efficacy or even cause the biocontrol treatment to support a net adverse effect on plant health. [ABSTRACT FROM AUTHOR]

Abstract: This study was conducted to assess evolutionary relationships, species diversity and trichothecene toxin potential of five Fusarium graminearum complex (FGSC) isolates identified as genetically novel during prior Fusarium head blight (FHB) surveys in Nepal and Louisiana. Results of a multilocus genotyping (MLGT) assay for B-trichothecene species determination indicated these isolates might represent novel species within the FGSC. GCPSR-based phylogenetic analyses of a 12-gene dataset, comprising portions of seven loci totaling 13.1kb of aligned DNA sequence data, provided strong support for the genealogical exclusivity of the Nepalese and Louisianan isolates. Accordingly, both species are formally recognized herein as novel FGSC species. Fusarium nepalense was resolved as the sister lineage of Fusarium ussurianum + Fusarium asiaticum within an Asian subclade of the FGSC. Fusarium louisianense was strongly supported as a reciprocally monophyletic sister of Fusarium gerlachii + F. graminearum, suggesting that this subclade might be endemic to North America. Multilocus Bayesian species tree analyses augment these results and provide evidence for a distinct lineage within F. graminearum predominately from the Gulf Coast of Louisiana. As predicted by the MLGT assay, mycotoxin analyses demonstrated that F. nepalense and F. louisianense could produce 15ADON and nivalenol, respectively, in planta. In addition, both species were only able to induce mild FHB symptoms on wheat in pathogenicity experiments. [Copyright &y& Elsevier]

Abstract: Fusarium head blight (FHB) caused by Gibberella zeae (anamorph= Fusarium graminearum) is a devastating disease that causes extensive yield and quality losses to wheat in humid and semi-humid regions of the world. Biological control has been demonstrated to be effective under laboratory conditions but a few biocontrol products have been effective under field conditions. The improvement in the physiological quality of biocontrol agents may improve survival under field conditions, and therefore, enhance biocontrol activity. Bacillus subtilis RC 218 and Brevibacillus sp. RC 263 were isolated from wheat anthers and showed significant effect on control of FHB under greenhouse assays. This study showed the effect of water availability measured as water activity (a W) using a growth medium modified with NaCl, glycerol and glucose on: (i) osmotic stress tolerance, (ii) viability in modified liquid medium, (iii) quantitative intracellular accumulation of betaine and ectoine and (iv) the biocontrol efficacy of the physiologically improved agents. Viability of B. subtilis RC 218 in NaCl modified media was similar to the control. Brevibacillus sp. RC 263 showed a limited adaptation to growth in osmotic stress. Betaine was detected in high levels in modified cells but ectoine accumulation was similar to the control cells. Biocontrol activity was studied in greenhouse assays on wheat inoculated at anthesis period with F. graminearum RC 276. Treatments with modified bacteria reduced disease severity from 60% for the control to below 20%. The physiological improvement of biocontrol agents could be an effective strategy to enhance stress tolerance and biocontrol activity under fluctuating environmental conditions. [Copyright &y& Elsevier]