The chromosome level whole genome sequence and the seconary matabolism gene cluster prediction of Fusarium meridionale, the pathogen causing maize ear rot.

Fusarium meridionale is one of the pathogens causing maize ear rot, it produce bioactive secondary metabolites may threaten humans food safty, however, the production mechanism of the secondary metabolites and their interaction with maize ear remains poorly understood. To facilitate related studies, we sequenced and assembled the genome of F. meridionale strain JX18-4. The size of F. meridionale JX18-4 genome is 37.11 Mbp, include four nuclear chromosome contigs that consists of 11920 coding genes and one mitochondrial contig. 95.64% gene synteny collinearity was found between the assembly and the reference genomes F. graminearum strain PH-1. Compared to the sequences of seconary matabolism gene clusters sequences reported previously, the stain JX18-4 was predicted potential producing 8 clusters, including nivalenol, zearalenone, aurofusarin, fusarielin, fusaristatin A, fusarin, fusarubin and butenolide. This study aims to reveal the molecular mechanism of secondary metabolites producing, and the genomic information of JX18-4 will provide resources for the study of biological control mechanisms and plant-microbe interactions.

A novel framework for three-dimensional electrical impedance tomography reconstruction of maize ear via feature reconfiguration and residual networks.

Electrical impedance tomography (EIT) provides an indirect measure of the physiological state and growth of the maize ear by reconstructing the distribution of electrical impedance. However, the two-dimensional (2D) EIT within the electrode plane finds it challenging to comprehensively represent the spatial distribution of conductivity of the intact maize ear, including the husk, kernels, and cob. Therefore, an effective method for 3D conductivity reconstruction is necessary. In practical applications, fluctuations in the contact impedance of the maize ear occur, particularly with the increase in the number of grids and computational workload during the reconstruction of 3D spatial conductivity. These fluctuations may accentuate the ill-conditioning and nonlinearity of the EIT. To address these challenges, we introduce RFNetEIT, a novel computational framework specifically tailored for the absolute imaging of the three-dimensional electrical impedance of maize ear. This strategy transforms the reconstruction of 3D electrical conductivity into a regression process. Initially, a feature map is extracted from measured boundary voltage via a data reconstruction module, thereby enhancing the correlation among different dimensions. Subsequently, a nonlinear mapping model of the 3D spatial distribution of the boundary voltage and conductivity is established, utilizing the residual network. The performance of the proposed framework is assessed through numerical simulation experiments, acrylic model experiments, and maize ear experiments. Our experimental results indicate that our method yields superior reconstruction performance in terms of root-mean-square error (RMSE), correlation coefficient (CC), structural similarity index (SSIM), and inverse problem-solving time (IPST). Furthermore, the reconstruction experiments on maize ears demonstrate that the method can effectively reconstruct the 3D conductivity distribution.

Bacterial endophytes inhabiting desert plants provide protection against seed rot caused by Fusarium verticillioides and promote growth in maize.

BACKGROUND: Fusarium maize ear and root rot disease caused by Fusarium verticillioides has become one of the most serious fungal diseases associated with maize production. Due to their abilities to promote plant development and manage diseases, bacterial endophytes provide a more promising approach for treating this vascular disease. RESULTS: This work was undertaken for the selection and identification of promising isolates as plant growth promoters and biocontrol agents against F. verticillioides in maize agroecosystems. A screening procedure consisting of in vitro and in situ tests was applied to 27 endophytic strains originating from desert plants: Euphorbia antiquorum, Calotropis procera, and Alcasia albida. In vitro studies indicated that the bacteria exhibited variable results in biocontrol, endophytism, and plant growth-promoting traits. In addition, in situ plant growth promotion and biocontrol experiments allowed the identification of the most promising bacterial endophytes. In vitro and in situ comparative study results indicated a low correlation. Our data revealed that in situ screening must be used as the method of selection of biocontrol agents against Fusarium ear and root rot disease. Based on in situ results, seven potent strains were selected and identified as Bacillus subtilis, Bacillus velezensis, Bacillus tequilensis, Stenotrophomonas maltophilia, and Klebsiella pneumoniae. CONCLUSION: The results of this study showed that the selected strains seem to be promising candidates to be exploited as biofertilizers and biocontrol agents against Fusarium maize ear and root rot disease. © 2023 Society of Chemical Industry.

MicroRNAs involved in the trans-kingdom gene regulation in the interaction of maize kernels and Fusarium verticillioides.

Maize ear rot is a widespread disease and the main pathogen is Fusarium verticillioides. Plant microRNAs (miRNAs) have great effects on disease resistance and it has been reported that maize miRNA participates in defense responses in maize ear rot. However, the trans-kingdom regulation of miRNAs between maize and F. verticillioides remains uncharacterized. In this study, the relationship between miRNA-like RNAs (milRNAs) of F. verticillioides and pathogenicity was investigated, followed by sRNA analysis and degradome sequencing of miRNA profiles and the target genes of maize and F. verticillioides after inoculation. It was found that the milRNA biogenesis positively regulated the pathogenicity of F. verticillioides by knocking out the gene FvDicer2-encoded Dicer-like protein in F. verticillioides. Following inoculation with F. verticillioides, 284 known and 6571 novel miRNAs were obtained in maize, including 28 miRNAs differentially expressed at multiple time points. The target genes of maize differentially expressed miRNAs in F. verticillioides mediated multiple pathways, including autophagy and MAPK signaling pathway. Fifty-one novel F. verticillioides milRNAs were predicted to target 333 genes in maize involved in MAPK signaling pathways, plant hormone signaling transduction and plant-pathogen interaction pathways. Additionally, the miR528b-5p in maize targeted the mRNA of FvTTP which encoded a twice transmembrane protein in F. verticillioides. The FvTTP-knockout mutants displayed decreased pathogenicity and reduced synthesis of fumonisins. Thus, by interfering with the translation of FvTTP, the miR528b-5p inhibited F. verticillioides infection. These findings suggested a novel function of miR528 in resisting F. verticillioides infection. The miRNAs identified in this research and their putative target genes can be used to further elucidate the trans-kingdom functions of microRNAs in plant pathogen interaction.

Asian Corn Borer (Ostrinia furnacalis) Infestation Increases Fusarium verticillioides Infection and Fumonisin Contamination in Maize and Reduces the Yield.

Field trials based on manual infestation of the Asian corn borer (ACB) (Ostrinia furnacalis [Guenée]) and Fusarium verticillioides (Nirenberg) atomization were conducted on four maize hybrids to investigate the relationship between ACB infestation and F. verticillioides infection, yield loss, and fumonisin contamination in maize. Analysis of fumonisins B1 and B2 was carried out using an LC-MS/MS system. In this study, manual ACB infestation significantly promoted F. verticillioides infection (both symptomatic and symptomless) and grain fumonisin levels. Ear rot incidence and severity, symptomless kernel infection, and fumonisin contamination were significantly correlated to each other and to ACB damage severity. Manual ACB infestation increased fumonisin levels from 580 to 4,418 µg/kg in 2018; 6,059 to 10,681 µg/kg in 2019 spring-sown maize (2019A); and 2,042 to 5,060 µg/kg in 2019 summer-sown maize (2019B), with the threshold of the European Union (EU) being 4,000 µg/kg. The threshold was exceeded in spring of 2019 in untreated controls. Regarding yield, significant negative correlation between ACB damage and ear weight was observed in three seasons. These results indicated that ACB infestation can lead to severe quality degradation and yield loss of maize. Kernel fumonisin levels may exceed the concentration threshold of the EU in certain conditions, threatening the health of livestock and humans. Measures should be taken to reduce ACB infestation to ensure food and feed security.

Genome-wide association studies revealed complex genetic architecture and breeding perspective of maize ear traits.

BACKGROUND: Maize (Zea Mays) is one of the world's most important crops. Hybrid maize lines resulted a major improvement in corn production in the previous and current centuries. Understanding the genetic mechanisms of the corn production associated traits greatly facilitate the development of superior hybrid varieties. RESULT: In this study, four ear traits associated with corn production of Nested Association Mapping (NAM) population were analyzed using a full genetic model, and further, optimal genotype combinations and total genetic effects of current best lines, superior lines, and superior hybrids were predicted for each of the traits at four different locations. The analysis identified 21-34 highly significant SNPs (-log10P > 5), with an estimated total heritability of 37.31-62.34%, while large contributions to variations was due to dominance, dominance-related epistasis, and environmental interaction effects ([Formula: see text] 14.06% ~ 49.28%), indicating these factors contributed significantly to phenotypic variations of the ear traits. Environment-specific genetic effects were also discovered to be crucial for maize ear traits. There were four SNPs found for three ear traits: two for ear length and weight, and two for ear row number and length. Using the Enumeration method and the stepwise tuning technique, optimum multi-locus genotype combinations for superior lines were identified based on the information obtained from GWAS. CONCLUSIONS: Predictions of genetic breeding values showed that different genotype combinations in different geographical regions may be better, and hybrid-line variety breeding with homozygote and heterozygote genotype combinations may have a greater potential to improve ear traits.

Transcriptome analysis of maize pathogen Fusarium verticillioides revealed FvLcp1, a secreted protein with type-D fungal LysM and chitin-binding domains, that plays important roles in pathogenesis and mycotoxin production.

Fusarium verticillioides is a key maize pathogen and produces fumonisins, a group of mycotoxins detrimental to humans and animals. Unfortunately, our understanding on how this fungus interacts with maize to trigger mycotoxin biosynthesis is limited. We performed a systematic computational network-based analysis of large-scale F. verticillioides RNA-seq datasets to identify gene subnetwork modules associated with virulence and fumonisin regulation. F. verticillioides was inoculated on two different maize lines, moderately resistant line hybrid 33K44 and highly susceptible line maize inbred line B73, to generate time-course RNA-Seq data. Among the highly discriminative subnetwork modules, we identified a putative hub gene FvLCP1, which encodes a putative a type-D fungal LysM protein with a signal peptide, three LysM domains, and two chitin binding domains. FvLcp1 is a unique protein that harbors these domains amongst five representative Fusarium species. FvLcp1 is a secreted protein important for fumonisin production with the LysM domain playing a critical role. The chitin-binding domain was essential for in vitro chitin binding. Using Magnaporthe oryzae, we learned that FvLcp1 accumulates in appressoria, suggesting that FvLcp1 is involved in host recognition and infection. Full length FvLcp1 suppressed BAX-triggered plant cell death in Nicotiana benthamiana. This unique type-D LysM secreted protein with a chitin-binding domain in F. verticillioides was shown to be potentially involved in suppressing host cell death and promoting fumonisin biosynthesis while the pathogen colonizes maize kernels.

Earbox, an open tool for high-throughput measurement of the spatial organization of maize ears and inference of novel traits.

BACKGROUND: Characterizing plant genetic resources and their response to the environment through accurate measurement of relevant traits is crucial to genetics and breeding. Spatial organization of the maize ear provides insights into the response of grain yield to environmental conditions. Current automated methods for phenotyping the maize ear do not capture these spatial features. RESULTS: We developed EARBOX, a low-cost, open-source system for automated phenotyping of maize ears. EARBOX integrates open-source technologies for both software and hardware that facilitate its deployment and improvement for specific research questions. The imaging platform consists of a customized box in which ears are repeatedly imaged as they rotate via motorized rollers. With deep learning based on convolutional neural networks, the image analysis algorithm uses a two-step procedure: ear-specific grain masks are first created and subsequently used to extract a range of trait data per ear, including ear shape and dimensions, the number of grains and their spatial organisation, and the distribution of grain dimensions along the ear. The reliability of each trait was validated against ground-truth data from manual measurements. Moreover, EARBOX derives novel traits, inaccessible through conventional methods, especially the distribution of grain dimensions along grain cohorts, relevant for ear morphogenesis, and the distribution of abortion frequency along the ear, relevant for plant response to stress, especially soil water deficit. CONCLUSIONS: The proposed system provides robust and accurate measurements of maize ear traits including spatial features. Future developments include grain type and colour categorisation. This method opens avenues for high-throughput genetic or functional studies in the context of plant adaptation to a changing environment.

A field-deployable method for single and multiplex detection of DNA or RNA from pathogens using Cas12 and Cas13.

For some Cas nucleases, trans-cleavage activity triggered by CRISPR/Cas-mediated cis-cleavage upon target nucleic acid recognition has been explored for diagnostic detection. Portable single and multiplex nucleic acid-based detection is needed for crop pathogen management in agriculture. Here, we harnessed and characterized RfxCas13d as an additional CRISPR/Cas nucleic acid detection tool. We systematically characterized AsCas12a, LbCas12a, LwaCas13a, and RfxCas13d combined with isothermal amplification to develop a CRISPR/Cas nucleic acid-based tool for single or multiplex pathogen detection. Our data indicated that sufficient detection sensitivity was achieved with just a few copies of DNA/RNA targets as input. Using this tool, we successfully detected DNA from Fusarium graminearum and Fusarium verticillioides and RNA from rice black-streaked dwarf virus in crude extracts prepared in the field. Our method, from sample preparation to result readout, could be rapidly and easily deployed in the field. This system could be extended to other crop pathogens, including those that currently lack a detection method and have metabolite profiles that make detection challenging. This nucleic acid detection system could also be used for single-nucleotide polymorphism genotyping, transgene detection, and qualitative detection of gene expression in the field.

Talaromyces funiculosus, a Novel Causal Agent of Maize Ear Rot and Its Sensitivity to Fungicides.

Ear rot is one of the most prevalent and destructive diseases of maize. During field surveys, it was found that a Penicillium ear rot broke out in some areas of Shanxi, Shaanxi, Hebei, and Tianjin in China, with an incidence of 3 to 90%. A Penicillium sp. was isolated from diseased kernels covered with greyish green mold, and three isolates were identified by morphologic and molecular characteristics. The pathogenicity of isolate ZBS205 to maize ears was further determined by artificial inoculation in a field. Furthermore, the sensitivity of isolate ZBS205 against six commonly used fungicides was also evaluated. According to macro- and micromorphologic characteristics, isolate ZBS205 was generally identical to Talaromyces funiculosus (teleomorph of Penicillium funiculosum). The partial gene sequences of the nuclear ribosomal ITS1-5.8S-ITS2 (ITS) region, ß-tubulin, putative ribosome biogenesis protein (Tsr1), and the second largest subunit of the RNA polymerase II (RPB2) from isolates ZBS205, D49-1, and S73-1 showed the highest nucleotide identity to T. funiculosus strain X33, and the phylogenetic analysis conducted by the neighbor-joining method with the combined data of the four genes demonstrated that these three isolates clustered with T. funiculosus strain X33. These results suggested that the fungus isolated from diseased maize kernels was T. funiculosus. Pathogenicity testing showed that the T. funiculosus isolate ZBS205 was pathogenic to maize ears, which showed symptoms of rotted cob and deteriorated kernels. This is the first report of T. funiculosus as the definitive pathogen causing maize ear rot. The result of fungal sensitivity against fungicides showed that pyraclostrobin exhibited the highest toxicity to mycelial growth and could be used as a candidate agent for the prevention and control of T. funiculosus ear rot. The results of the present study provide a basis for understanding ear rot caused by T. funiculosus, and they should play an important role in disease management.

Single-cell RNA sequencing of developing maize ears facilitates functional analysis and trait candidate gene discovery.

Crop productivity depends on activity of meristems that produce optimized plant architectures, including that of the maize ear. A comprehensive understanding of development requires insight into the full diversity of cell types and developmental domains and the gene networks required to specify them. Until now, these were identified primarily by morphology and insights from classical genetics, which are limited by genetic redundancy and pleiotropy. Here, we investigated the transcriptional profiles of 12,525 single cells from developing maize ears. The resulting developmental atlas provides a single-cell RNA sequencing (scRNA-seq) map of an inflorescence. We validated our results by mRNA in situ hybridization and by fluorescence-activated cell sorting (FACS) RNA-seq, and we show how these data may facilitate genetic studies by predicting genetic redundancy, integrating transcriptional networks, and identifying candidate genes associated with crop yield traits.

A high-throughput and low-cost maize ear traits scorer.

In this study, based on automatic control and image processing, a high-throughput and low-cost maize ear traits scorer (METS) was developed for the automatic measurement of 34 maize ear traits. In total, 813 maize ears were measured using METS, and the results showed that the square of the correlation coefficient (R2) of the manual measurements versus the automatic measurements for ear length, ear diameter, and kernel thickness were 0.96, 0.79, and 0.85, respectively. These maize ear traits could be used to classify the type, and the results showed that the classification accuracy of the support vector machine (SVM) model for the test set was better than that of the random forest (RF) model. In addition, the general applicability of the image analysis pipeline was also demonstrated on other independent maize ear phenotyping platforms. In conclusion, equipped with image processing and automatic control technologies, we have developed a high-throughput method for maize ear scoring, which could be popularized in maize functional genetics, genomics, and breeding applications. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-021-01205-4.

First Report of Fusarium miscanthi Causing Ear Rot on Maize in China.

Maize (Zea mays L.), an important food and feed crop worldwide, can be infected by Fusarium pathogens that can contaminate grain with mycotoxins. From August to October in 2018 and 2019, a field survey for maize ear rot was conducted in 76 counties of Guizhou province. The incidence ranged from 3% to 15% at individual fields in different areas. A total of 175 diseased maize ears with similar symptoms, including kernels covered with white, pink or salmon-colored mold or exhibiting a white streaking ("starburst") symptom, were collected from fields. Symptomatic kernels were surface-sterilized by soaking for 30 s in 70% alcohol and for another 2 min in 2% sodium hypochlorite solution, followed by five rinses with sterile water. Each kernel was cut into half and placed on potato dextrose agar (PDA). After incubation at 28 °C in the dark for 5 days, colonies displaying morphological characteristics of Fusarium were transferred to fresh PDA (Leslie and Summerell 2006). Single-sporing was conducted to purify the putative Fusarium colonies. A total of 120 isolates belonged to 16 Fusarium species were determined and F. meridionale was the dominant species. Five isolates from Huaxi district of Guiyang City were identified as F. miscanthi (Gams et al. 1999). Colonies on PDA were white and floccose, and pigmentation as viewed from the underside of the Petri dish was violet. The average growth rate was 7.5-8.0 mm/day at 28 °C in the dark. In cultures grown on PDA, 0-1-septate microconidia were produced in slimy heads. Microconidia were clavate to fusiform with a truncate base and a broadly rounded tip, 4.8-13.3 µm × 1.8-3.3 µm (n=110). In cultures grown on half-strength CMC broth (Xu et al. 2010), macroconidia were mostly 3-septate, almost straight for most of the length, with a slightly foot-shaped basal cell and curved apical cell that gradually tapered, 17.8-71.3 µm × 2.0-4.3 µm (n=78). The identity of the fungus was confirmed by sequence comparison of the partial translation elongation factor-1α (TEF-1α), RNA polymerase II subunit (RPB2), mitochondrial small subunit rDNA (mtSSU) and ß-tubulin genes (Mirete et al. 2004; O'Donnell et al. 2010; O'Donnell and Cigelnik 1997). BLASTn searches of GenBank, using the partial TEF-1α (MN750829), RPB2 (MN750834), mtSSU (MT594104) and ß-tubulin (MT584781) sequences of representative isolate GYHXB03 as the queries, revealed 99.84%, 99%, 100% and 100% sequence identity, respectively, to F. miscanthi NRRL 26231 accessions AF324331, JX171634, AF060371 and AF060384. Inoculum of isolate GYHXB03 was prepared (Xu et al. 2010), and a pathogenicity test was conducted on maize hybrid "Shundan7" and repeated twice. A 106/mL spore suspension (2 mL) or sterile water was injected into each of 8 maize ears through the silk channel at the blister stage of reproductive development in field (Duan et al. 2019). After three weeks, typical Fusarium kernel rot symptoms the same as those previously shown in the field was observed on all pathogen-inoculated plants, while the controls were asymptomatic. The pathogens re-isolated from two diseased kernels were identified as F. miscanthi based on morphology and TEF-1α and mtSSU analyses. F. miscanthi was first isolated from Miscanthus sinensis in Denmark (Gams et al. 1999), and also identified from M. × giganteus rhizomes in Belgium (Scauflaire et al. 2013). To our knowledge, this is the first report of F. miscanthi causing maize ear rot in China. This disease should be monitored in Guizhou due to its threat to maize production.

Occurrence, Pathogenicity, and Mycotoxin Production of Fusarium temperatum in Relation to Other Fusarium Species on Maize in Germany.

Fusarium subglutinans is a plant pathogenic fungus infecting cereal grain crops. In 2011, the species was divided in Fusarium temperatumsp. nov. and F. subglutinans sensu stricto. In order to determine the occurrence and significance of F. temperatum and F. subglutinans on maize, a monitoring of maize ears and stalks was carried out in Germany in 2017 and 2018. Species identification was conducted by analysis of the translation elongation factor 1α (TEF-1α) gene. Ninety-four isolates of F. temperatum and eight isolates of F. subglutinans were obtained during two years of monitoring from 60 sampling sites in nine federal states of Germany. Inoculation of maize ears revealed a superior aggressiveness for F. temperatum, followed by Fusarium graminearum, Fusarium verticillioides, and F. subglutinans. On maize stalks, F. graminearum was the most aggressive species while F. temperatum and F. subglutinans caused only small lesions. The optimal temperature for infection of maize ears with F. temperatum was 24 °C and 21 °C for F. subglutinans. All strains of F. temperatum and F. subglutinans were pathogenic on wheat and capable to cause moderate to severe head blight symptoms. The assessment of mycotoxin production of 60 strains of F. temperatum cultivated on rice revealed that all strains produced beauvericin, moniliformin, fusaric acid, and fusaproliferin. The results demonstrate a higher prevalence and aggressiveness of F. temperatum compared to F. subglutinans in German maize cultivation areas.

High-Resolution Melting (HRM) Curve Assay for the Identification of Eight Fusarium Species Causing Ear Rot in Maize.

Maize plants are often infected with fungal pathogens of the genus Fusarium. Taxonomic characterization of these species by microscopic examination of pure cultures or assignment to mating populations is time-consuming and requires specific expertise. Reliable taxonomic assignment may be strengthened by the analysis of DNA sequences. Species-specific PCR assays are available for most Fusarium pathogens, but the number of species that infect maize increases the labor and costs required for analysis. In this work, a diagnostic assay for major Fusarium pathogens of maize based on the analysis of melting curves of PCR amplicons was established. Short segments of genes RPB2 and TEF-1α, which have been widely used in molecular taxonomy of Fusarium, were amplified with universal primers in a real-time thermocycler and high-resolution melting (HRM) curves of the products were recorded. Among major Fusarium pathogens of maize ears, F. cerealis, F. culmorum, F. graminearum, F. equiseti, F. poae, F. temperatum, F. tricinctum, and F. verticillioides, all species except for the pair F. culmorum/F. graminearum could be distinguished by HRM analysis of a 304 bp segment of the RPB2 gene. The latter two species could be differentiated by HRM analysis of a 247 bp segment of the TEF-1α gene. The assay was validated with DNA extracted from pure cultures of fungal strains, successfully applied to total DNA extracted from infected maize ears and also to fungal mycelium that was added directly to the PCR master mix ("colony PCR"). HRM analysis thus offers a cost-efficient method suitable for the diagnosis of multiple fungal pathogens.

Management of Euxesta spp. in Sweet Corn with McPhail Traps.

Pests attacking the ear of sweet corn, such as Helicoverpa and Euxesta species, cause economic losses for the producer and the processing industry. Feeding on the style-stigmata preventing fertilization and on the developing grain and the association with pathogens are the main causes of product depreciation. The traditional control such as spraying with chemicals is not effective, even with several applications directed to the corn ear. Bacillus thuringiensis (Bt) corn also does not reach the fly. McPhail traps that have been used to monitor the pest can be a control strategy. This work evaluated the efficiency of food attractants placed inside McPhail traps to remove adult insects, in order to reduce ear damage. Twelve McPhail-type traps were installed in a randomized complete block design containing Bio Anastrepha® alone or combined with different doses of insecticide. Every 10 days, all the captured insects were counted and separated by species and sex. Only Euxesta eluta and Euxesta mazorca were found. The occurrence of insects was greater in the period between silk emergence and grain filling. The number of females was higher, probably due to the need to feed before oviposition. The number of E. mazorca females caught in the treatment containing only Bio Anastrepha® was higher compared with that of others. The mean ear damage was very low, and there was no interaction between the production parameters and the distance between the trap and the harvested plant. In short, the use of McPhail trap containing food attractants may be a viable alternative to control corn silk flies.

Mycotoxins in Flanders' Fields: Occurrence and Correlations with Fusarium Species in Whole-Plant Harvested Maize.

Mycotoxins are well-known contaminants of several food- and feedstuffs, including silage maize for dairy cattle. Climate change and year-to-year variations in climatic conditions may cause a shift in the fungal populations infecting maize, and therefore alter the mycotoxin load. In this research, 257 maize samples were taken from fields across Flanders, Belgium, over the course of three years (2016-2018) and analyzed for 22 different mycotoxins using a multi-mycotoxin liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. DNA of Fusarium graminearum, F. culmorum and F. verticillioides was quantified using the quantitative polymerase chain reaction (qPCR). Multi-mycotoxin contamination occurred frequently, with 47% of samples containing five or more mycotoxins. Nivalenol (NIV) was the most prevalent mycotoxin, being present in 99% of the samples, followed by deoxynivalenol (DON) in 86% and zearalenone (ZEN) in 50% of the samples. Fumonisins (FUMs) were found in only 2% of the samples in the wet, cold year of 2016, but in 61% in the extremely hot and dry year of 2018. Positive correlations were found between DON and NIV and between F. graminearum and F. culmorum, among others. FUM concentrations were not correlated with any other mycotoxin, nor with any Fusarium sp., except F. verticillioides. These results show that changing weather conditions can influence fungal populations and the corresponding mycotoxin contamination of maize significantly, and that multi-mycotoxin contamination increases the risk of mycotoxicosis in dairy cattle.

Isolation, Molecular Identification and Mycotoxin Profile of Fusarium Species Isolated from Maize Kernels in Iran.

Fusarium species are among the most important fungal pathogens of maize, where they cause severe reduction of yield and accumulation of a wide range of harmful mycotoxins in the kernels. In order to identify the Fusarium species and their mycotoxin profiles associated to maize ear rot and kernel contamination in Iran, a wide sampling was carried out from field in ten major maize-producing provinces in Iran, during 2015 and 2016. From 182 samples of maize kernels, 551 strains were isolated and identified as belonging to Fusarium genus. Among the 234 representative strains identified at species level by translation elongation factor (EF-1α) sequences, the main Fusarium species were F. verticillioides and F. proliferatum, together representing 90% of the Iranian Fusarium population, and, to a lesser extent, F. incarnatum equiseti species complex (FIESC), F. thapsinum and F. redolens. Fumonisin (FBs) production by F. verticillioides and F. proliferatum representative strains was analysed, showing that all strains produced FB1. None of F. verticillioides strains produced FB2 nor FB3, while both FB2 and FB3 were produced only by F. proliferatum. Total mean of FBs production by F. verticillioides was higher than F. proliferatum. The occurrence of different Fusarium species on Iranian maize is reason of great concern because of the toxigenic risk associated to these species. Moreover, the diversity of the species identified increases the toxigenic risk associated to Fusarium contaminated maize kernels, because of the high possibility that a multi-toxin contamination can occur with harmful consequences on human and animal health.

Fumonisin Production by Fusarium verticillioides in Maize Genotypes Cultivated in Different Environments.

Fumonisins are mycotoxins (MTs) produced mainly by the fungus Fusarium verticillioides, the main pathogens of maize which cause ear rot. The aim of this work was to evaluate some factors that may lead to high fumonisin production by F. verticillioides in maize grains, correlating the pathogen inoculation method with different genotypes grown in four Brazilian states. Experiments were conducted in 2015-2016 in maize crops from experimental maize fields located in four distinct states of Brazil. Results showed that contamination by fumonisin mycotoxins occurred even on symptomatic or asymptomatic grains. In all municipalities, the samples showed levels of fumonisin B1 that were higher than would be tolerable for the human consumption of corn products (the current tolerance limit for fumonisin is 1.5 µg g-1). High severity of grains infected with F. verticillioides does not always show high concentrations of fumonisins. Environments with higher temperatures may influence the production of high concentrations of fumonisin in maize hybrids. Spray inoculation methods and inoculation at the center of spikes did not influence fumonisin concentrations. Results showed that the hybrids P3630H, P32R48 and P3250 presented higher disease severity, as well as higher mycotoxin levels in the studied locations with higher temperatures.

Occurrence of Mycotoxigenic Fusarium Species and Competitive Fungi on Preharvest Maize Ear Rot in Poland.

Maize has become one of the most important crops for food and feed production-both as a silage and crop residue worldwide. The present study aimed to identify the co-occurrence of Fusarium subglutinans, Fusarium verticillioides, Trichoderma atroviride, Sarocladium zeae, and Lecanicillium lecanii on maize ear rot. Further, the accumulation of mycotoxins as secondary metabolites of Fusarium spp. in maize ear samples was also analyzed. Maize ear samples were collected between 2014 and 2017 from two main maize growing areas in Poland (Greater Poland and Silesia region). A significant difference was found in the frequency of two main Fusarium spp. that infect maize ears, namely F. subglutinans and F. verticillioides. In addition to Fusarium spp. T. atroviride, S. zeae, and L. lecanii were also identified. T. atroviride species was found in 14% of maize samples examined between 2014 and 2017, particularly with a high percentage of Trichoderma spp. recorded in 2014, i.e., in 31% of samples. However, mycotoxin content (beauvericin and fumonisins) varied, depending on both the location and year of sampling. The interaction of fungi and insects inhabiting maize ear and kernel is very complex and not yet elucidated. Therefore, further research is required in this area.