Geographic Distribution of Trichothecene Chemotypes of the Fusarium graminearum Species Complex in Major Winter Wheat Production Areas of China

Genome Analyses Reveal the Secondary Metabolites that Potentially Influence the Geographical Distribution of Fusarium pseudograminearum Populations

Fusarium crown rot (FCR), caused by Fusarium pseudograminearum, significantly impacts wheat yield and quality in China's Huanghuai region. The rapid F. pseudograminearum epidemic and FCR outbreak within a decade remain unexplained. In this study, two high-quality, chromosome-level genomes of F. pseudograminearum strains producing 3-acetyl-deoxynivalenol (3AcDON) and 15-acetyl-deoxynivalenol (15AcDON) toxins were assembled. Additionally, 38 related strains were resequenced. Genomic differences such as single nucleotide polymorphisms (SNPs), insertions/deletions (indels), and structural variations (SVs) among F. pseudograminearum strains were analyzed. The whole-genome SNP locus-based population classification mirrored the toxin chemotype (3AcDON and 15AcDON)-based classification, indicating the presence of genes associated with the trichothecene toxin gene cluster. Further analysis of differential SNP, indel, and SV loci between the 3AcDON and 15AcDON populations revealed a predominant connection to secondary metabolite synthesis genes. Notably, the majority of the secondary metabolite biosynthesis gene cluster loci were located in SNP-dense genomic regions, suggesting high mutability and a possible contribution to F. pseudograminearum population structure and environmental adaptability. This study provides insightful perspectives on the distribution and evolution of F. pseudograminearum and for forecasting the spread of wheat FCR, thereby aiding in the development of preventive measures and control strategies.

A nivalenol imprinted quartz crystal microbalance sensor based on sulphur-incorporating cobalt ferrite and its application to rice samples

Nivalenol as a mycotoxin pesticide is toxic to humans and animals and causes major health problems including hemorrhage, anemia, and vomiting. Thus, the need for fast and reliable analytical systems in terms of the management of health risks resulting from nivalenol exposure has increased in recent years. The aim of this study involved a novel molecularly imprinted quartz crystal microbalance sensor preparation based on sulphur-incorporating cobalt ferrite for nivalenol detection in rice samples. For this aim, cobalt ferrite and sulfur incorporated cobalt ferrite were successfully synthesized by sol-gel and calcination methods, respectively. Then, nivalenol imprinted quartz crystal microbalance chips based on cobalt ferrite and sulfur incorporated cobalt ferrite were prepared by an ultraviolet polymerization technique including N,N'-azobisisobutyronitrile as the initiator, ethylene glycol dimethacrylate as the cross-linker, methacryloylamidoglutamic acid as the monomer, and nivalenol as the analyte. After some spectroscopic, electrochemical and microscopic characterization studies, the developed sensor was applied to rice grain samples for the determination of nivalenol. The linearity of the prepared sensor was observed to be 1.0-10.0 ng L-1 and the limit of quantification and detection limit were found to be 1.0 and 0.33 ng L-1, respectively. Finally, the high selectivity, repeatability, and stability of the prepared sensor based on sulphur-incorporating cobalt ferrite and a molecularly imprinted polymer can ensure safe food consumption worldwide.

Nivalenol Mycotoxin Concerns in Foods: An Overview on Occurrence, Impact on Human and Animal Health and Its Detection and Management Strategies

Mycotoxins are secondary metabolites produced by fungi that infect a wide range of foods worldwide. Nivalenol (NIV), a type B trichothecene produced by numerous Fusarium species, has the ability to infect a variety of foods both in the field and during post-harvest handling and management. NIV is frequently found in cereal and cereal-based goods, and its strong cytotoxicity poses major concerns for both human and animal health. To address these issues, this review briefly overviews the sources, occurrence, chemistry and biosynthesis of NIV. Additionally, a brief overview of several sophisticated detection and management techniques is included, along with the implications of processing and environmental factors on the formation of NIV. This review’s main goal is to offer trustworthy and current information on NIV as a mycotoxin concern in foods, with potential mitigation measures to assure food safety and security.

Fusarium head blight in the Russian Far East: 140 years after description of the 'drunken bread' problem

The first appearance of Fusarium head blight (FHB)—and the beginning of scientific research of this disease—occurred the Far East region of Russia at the end of the 19th century. In the summer of 2019, in the Amur region, which comprises 60–70% of grain production in the Russian Far East, flooding caused a state of emergency. The quality of wheat and barley grains grown under natural conditions of FHB outbreaks, including grain infection, fungal species composition, DNA content of F. graminearum and chemotypes, and the presence of various mycotoxins, was studied. Fusarium infection rates reached extremely high percentages, 51–98%, the majority of which were F. graminearum infections. The amount of F. graminearum DNA in wheat grain samples was higher than in the barley grain samples and averaged 6.1 and 2.1 pg/ng, respectively. The content of deoxynivalenol (DON) in the wheat samples reached 13,343 ppb and in barley reached 7,755 ppb. A multilocus genotyping assay was conducted on the partially sequenced fragments of the translation elongation factor EF-1a, ammonium ligase gene, reductase gene, and 3-O-acetyltransferase gene in 29 Fusarium graminearum sensu lato strains from the grain harvested in the Amur region. All strains from the Far East region were characterized as F. graminearum sensu stricto; 70% were the 15-AcDON chemotype, while the other strains were the 3-AcDON chemotype. According to the results, after 140 years of study of FHB, we are still not very successful in controlling this disease if conditions are favorable for pathogen development. Even at present, some of the grain harvested must be destroyed, as high contamination of mycotoxins renders it unusable.

The Distribution of Fusarium graminearum and Fusarium asiaticum Causing Fusarium Head Blight of Wheat in Relation to Climate and Cropping System

In the main wheat production area of China (the Huang Huai Plain [HHP]), both Fusarium graminearum and Fusarium asiaticum, the causal agents of Fusarium head blight (FHB), are present. We investigated whether the relative prevalence of F. graminearum and F. asiaticum is related to cropping systems and/or climate factors. A total of 1,844 Fusarium isolates were obtained from 103 fields of two cropping systems: maize-wheat and rice-wheat rotations. To maximize the differences in climatic conditions, isolates were sampled from the north and south HHP regions. Based on the phylogenetic analysis of EF-1α and Tri101 sequences, 1,207 of the 1,844 isolates belonged to F. graminearum, and the remaining 637 isolates belonged to F. asiaticum. The former was predominant in the northern region: 1,022 of the 1,078 Fusarium isolates in the north were F. graminearum. The latter was predominant in the southern region: 581 of the 766 Fusarium isolates belonged to F. asiaticum. Using an analysis based on generalized linear modeling, the relative prevalence of the two species was associated more with climatic conditions than with the cropping system. F. graminearum was associated with drier conditions and cooler conditions during the winter but also with warmer conditions in the infection and grain-colonization period as well as with maize-wheat rotation. The opposite was true for F. asiaticum. Except for the 15-acetyldeoxynvalenol genotype, the trichothecene chemotype composition of F. asiaticum differed between the two cropping systems. The 3-acetyldeoxynivalenol genotype was more prevalent in the maize-wheat rotation, whereas the nivalenol genotype was more prevalent in the rice-wheat rotation. The results also suggested that environmental conditions in the overwintering period appeared to be more important than those in the infection, grain-colonization, and preanthesis sporulation periods in affecting the relative prevalence of F. graminearum and F. asiaticum. More research is needed to study the effect of overwintering conditions on subsequent epidemic in the following spring.

Simultaneous quantitation of 3ADON and 15ADON chemotypes of DON-producing Fusarium species in Chinese wheat based on duplex droplet digital PCR assay

Pathogens within Fusarium species are the primary agents of Fusarium head blight (FHB) of wheat, which bring about yield reduction and deoxynivalenol (DON) contamination and are of great concern worldwide. DON-producing Fusarium species can be classified into 3-acetyldeoxynivalenol (3ADON) and 15-acetyldeoxynivalenol (15ADON) chemotypes according to the trichothecene metabolites they produce. The detection of these two chemotypes of pathogens is paramount to the successful implementation of disease management strategies and pathogen-related DON forecasting models. In this study, a duplex droplet digital PCR (duplex ddPCR) assay was developed that allowed for the simultaneous quantitation of 3ADON and 15ADON chemotypes of DON-producing Fusarium species. The assay specificity was tested against 30 isolates of target Fusarium species and several non-target Fusarium species that are frequently isolated from wheat in China. Analyzing 90 wheat samples collected from the North China plain and Yangtze River plain demonstrated that the duplex ddPCR assay coupled with magnetic bead-based DNA extraction was competent for investigating composition of 3ADON and 15ADON chemotypes in Chinese wheat. This assay will be useful for monitoring the epidemic and geographic distribution of 3ADON and 15ADON chemotypes of FHB pathogens, which will help with the disease control and DON management.

Occurrence, mitigation and in vitro cytotoxicity of nivalenol, a type B trichothecene mycotoxin - Updates from the last decade (2010-2020)

The present review aims to give an overview of the literature of the last decade (2010-2020) concerning the occurrence of the type B trichothecene mycotoxin nivalenol (NIV) and its in vitro toxicity, with the purpose of updating information regarding last researches on this mycotoxin. The most recent studies on the possible methods for preventing Fusarium spp. growth and NIV production are also discussed. Recently, various environmental factors have been shown to influence strongly NIV occurrence. However, Fusarium spp. of the NIV genotype have been found almost worldwide. With regard to NIV cytotoxicity, NIV has been reported to cause a marked decrease in cell proliferation in different mammalian cells. In particular, the recent data suggest that organs containing actively proliferating cells represent the main targets of NIV. Moreover, NIV resulted to cause immunosuppression, gastrointestinal toxicity and genotoxicity. However, sufficient evidence of carcinogenicity in humans is currently lacking, and the International Agency for Research on Cancer (IARC) classifies it as a group 3 carcinogen. Further researches and the discovery of effective treatment strategies to prevent NIV contamination and to counteract its toxicity are urgently required against this common food-borne threat to human health and livestock.

Identification of New Sources of Resistance to Crown Rot and Fusarium Head Blight in Wheat

Crown rot (CR) and Fusarium head blight (FHB) are two serious wheat diseases caused by Fusarium pathogens in China. To identify new resistant sources for CR and FHB, 205 Chinese wheat cultivars collected from Huang-Huai wheat-growing region in China were screened for resistance. Cunmai633, LS4607, Pubing01, and Hongyun2 showed seedling resistance to CR with disease index (DI) less than 0.25. Sixteen cultivars showed adult-plant resistance to CR with DI lower than 0.10. Twenty-six cultivars showed moderate resistance to CR at seedling stage with DI from 0.26 to 0.35, and 63 cultivars showed moderate adult-plant resistance with DI from 0.11 to 0.20. Among them, Cunmai633, LS4607, Pubing01, Xinong916, Zhengda161, Xumai14017, Zhengpinmai30, Bainong8822, Jimai216, Huacheng865, Fengyumai5, and Tianmin319 showed resistance or moderate resistance to CR at both seedling and adult plant stages, with Cunmai633 showing the best resistance. Most of the cultivars (>76%) were susceptible to FHB in both the 2017 and 2018 experiments with DI > 0.40. However, some cultivars demonstrated excellent FHB resistance. For example, Zhongyu1526, Tianminxiaoyan369, and Yangao168 were resistant (DI ≤ 0.25) in 2017 and moderately resistant (0.26 ≤ DI ≤ 0.40) in 2018; Zhongwo9 was moderately resistant in 2017 (DI = 0.38) and resistant in 2018 (DI = 0.25). Eight cultivars (Cunmai608, Zhengmai162, Minfeng266, Junda159, LS4607, Deyan1603, Pumai1165, and Fengmai12) showed moderate FHB resistance with DI lower than 0.40 in both experiments. LS4607 showed moderate resistance to both diseases. The resistant cultivars identified in this study can be used for mapping the resistance genes and improving resistance to CR and/or FHB.

Resistance to Fusarium head blight and mycotoxin accumulation among 129 wheat cultivars from different ecological regions in China

A total of 129 wheat cultivars collected from local breeders in four ecological regions in China was evaluated for Fusarium head blight resistance after natural infection under epidemic conditions. The disease index was scored and seven toxins concentrations were determined by UPLC-MS/MS. The disease index ranged from 6.3 to 80.9% and a strong correlation was found between the regions from which the cultivars originate and disease index. The middle and lower reaches of Yangtze River Region showed the highest disease resistance, followed by the upper reaches of the Yangtze River Region. FHB resistance of cultivars from northern and southern Huanghuai Region was lowest and all cultivars in these regions are highly or moderately susceptible. Disease index was significantly correlated with toxin accumulation on nation scale, but no clear correlation was found within most ecological regions. The toxin accumulation was also not well correlated with resistant levels. As the incidence of FHB has increased dramatically over the last decade, improved FHB resistance in cultivars is urgently needed. We recommend that besides scoring for disease index also mycotoxin accumulation in cultivars is incorporated in breeding procedures and the evaluation of cultivars.

Occurrence of Fusarium mycotoxins and toxigenic Fusarium species in freshly harvested rice in Jiangsu, China

In 2017, 236 rice samples were collected from 42 counties in Jiangsu province, China, and analysed for Fusarium mycotoxins. Mycotoxin analyses showed that deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), nivalenol (NIV), fusarenone X (FUS-X), zearalenone (ZEA), fumonisins (including FB1, FB2, and FB3), and beauvericin (BEA) were present in unhusked rice samples. Regional differences in mycotoxin contamination of unhusked rice were attributed to differences in precipitation during rice anthesis and agricultural practices among the three study regions. Importantly, the mean concentrations of DON, NIV, ZEA, and fumonisins in white rice were significantly lower than those in unhusked rice, and the relative proportion of the toxins in rice by-products exceeded 84%. Fusarium isolates were then obtained from the unhusked rice samples; Fusarium asiaticum was the most common, followed by Fusarium fujikuroi, Fusarium proliferatum, Fusarium verticillioides, and Fusarium commune. Genotype and chemical analyses of mycotoxins showed that most F. asiaticum isolates (71%) were 3-ADON chemotypes; the remainder were NIV producers. All of the F. proliferatum and F. verticillioides isolates, and most of the F. fujikuroi isolates produce fumonisins, and most of the three species coproduced BEA. The present study is the first to evaluate Fusarium mycotoxins and toxigenic Fusarium species from rice freshly harvested in Jiangsu province, China. The results of this study improve our understanding the population dynamics of Fusarium species in rice and the development of effective control measures.

Fusarium Toxins in Chinese Wheat since the 1980s

Wheat Fusarium head blight (FHB), caused by Fusarium species, is a widespread and destructive fungal disease. In addition to the substantial yield and revenue losses, diseased grains are often contaminated with Fusarium mycotoxins, making them unsuitable for human consumption or use as animal feed. As a vital food and feed ingredient in China, the quality and safety of wheat and its products have gained growing attention from consumers, producers, scientists, and policymakers. This review supplies detailed data about the occurrence of Fusarium toxins and related intoxications from the 1980s to the present. Despite the serious situation of toxin contamination in wheat, the concentration of toxins in flour is usually lower than that in raw materials, and food-poisoning incidents have been considerably reduced. Much work has been conducted on every phase of toxin production and wheat circulation by scientific researchers. Regulations for maximum contamination limits have been established in recent years and play a substantial role in ensuring the stability of the national economy and people's livelihoods.

Comparative Pathogenicity of Fusarium graminearum Isolates from Wheat Kernels in Korea

Fusarium head blight (FHB) caused by Fusarium species is a major disease of wheat and barley around the world. FHB causes yield reductions and contamination of grains with trichothecene mycotoxins including; nivalenol (NIV), deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON), and 15-acetylde-oxynivalenol (15-ADON). The objectives of this study were to identify strains of F. graminearum isolated in Korea from 2012-harvested wheat grain and to test the pathogenicity of these NIV- and DON-producing isolates. Three hundred and four samples of wheat grain, harvested in 2012 in Chungnam, Chungbuk, Gyeongnam, Jeonbuk, Jeonnam, and Gangwon provinces were collected. We recovered 44 isolates from the 304 samples, based on the PCR amplification of internal transcribed spacer (ITS) rRNA region and sequencing. Our findings indicate that F. asiaticum was the predominant (95% of all isolates) species in Korea. We recovered both F. asiaticum and F. graminearum from samples collected in Chungnam province. Of the 44 isolates recovered, 36 isolates had a NIV genotype while 8 isolates belonged to the DON genotype (3-ADON and 15-ADON). In order to characterize the pathogenicity of the strains collected, disease severity was assessed visually on various greenhouse-grown wheat cultivars inoculated using both NIV- and DON-producing isolates. Our results suggest that Korean F. graminearum isolates from wheat belong to F. asiaticum producing NIV, and both F. graminearum and F. asiaticum are not significantly different on virulence in wheat cultivars.

The Major Fusarium Species Causing Maize Ear and Kernel Rot and Their Toxigenicity in Chongqing, China

Fusarium verticillioides, F. proliferatum, and F. meridionale were identified as the predominant fungi among 116 Fusarium isolates causing maize ear and kernel rot, a destructive disease in Chongqing areas, China. The toxigenic capability and genotype were determined by molecular amplification and toxin assay. The results showed that the key toxigenic gene FUM1 was detected in 47 F. verticillioides and 19 F. proliferatum isolates. Among these, F. verticillioides and F. proliferatum isolates mainly produced fumonisin B₁, ranging from 3.17 to 1566.44, and 97.74 to 11,100.99 µg/g for each gram of dry hyphal weight, with the averages of 263.94 and 3632.88 µg/g, respectively, indicating the F. proliferatum isolates on average produced about an order of magnitude more fumonisins than F. verticillioides did in these areas, in vitro. Only NIV genotype was detected among 16 F. meridionale and three F. asiaticum isolates. Among these, 11 F. meridionale isolates produced NIV, varying from 17.40 to 2597.34 µg/g. ZEA and DON toxins were detected in 11 and 4 F. meridionale isolates, with the toxin production range of 8.35-78.57 and 3.38-33.41 µg/g, respectively. Three F. asiaticum isolates produced almost no mycotoxins, except that one isolate produced a small amount of DON. The findings provide us with insight into the risk of the main pathogenic Fusarium species and a guide for resistance breeding in these areas.

Identification and trichothecene genotypes of Fusarium graminearum species complex from wheat in Taiwan

BACKGROUND

Fusarium head blight (FHB) of wheat caused by Fusarium graminearum species complex (FGSC) is a devastating disease worldwide. The pathogens not only reduce the yield of wheat, but also impact the quality of wheat by contamination with trichothecene mycotoxins. A systematic investigation on the pathogens of FHB in Taiwan is lacking. Here, molecular and morphological approaches were used to identify species of the Taiwanese FGSC isolates and determine their trichothecene genotypes.

RESULTS

In this study, a total of 195 isolates of FGSC from diseased wheat were collected from 8 areas of northern and central Taiwan. All isolates were subjected to seedling inoculation for verification of pathogenicity. The pathogenic isolates were genetically characterized by sequence characterized amplified region (SCAR), PCR- restriction fragment length polymorphism (RFLP), phylogenetic analysis and fixed nucleotides to clarify their phylogenetic species, and by PCR assays of TRI genes to determine trichothecene genotypes. They were identified as F. asiaticum, F. graminearum sensu stricto, F. meridionale and an unknown species. Isolates of F. asiaticum were the major causal agents (98%) in this investigated population and were comprised of SCAR type 5 (75%), SCAR type 4 (21%) and SCAR type 3 (2%). Their trichothecene genotypes were either 15-acetyl-deoxynivalenol (15-ADON) (83%) or nivalenol (NIV) genotype (17%). These genetic characterizations indicated that F. asiaticum (15-ADON SCAR type 5) accounts for 60% of this Taiwanese population. Virulence assay on wheat heads indicated virulence of F. asiaticum isolates in subpopulations divided by SCAR types or trichothecene genotypes were comparable, suggesting other factors influence the unequal subpopulation sizes.

CONCLUSIONS

This is the first study that FGSC isolates in Taiwan were systematically collected and characterized. In addition to F. graminearum sensu stricto and F. meridionale, F. asiaticum with 15-ADON genotype was identified as the predominate species in Taiwan. In contrast to Chinese and Japanese populations that F. asiaticum isolates were typically of 3-ADON or NIV genotype, the predominate 15-ADON genotype in Taiwanese population was unique among F. asiaticum populations and represented the southernmost 15-ADON genotype population in East Asia.

Analysis of Fusarium graminearum Species Complex from Wheat-Maize Rotation Regions in Henan (China)

Fusarium head blight (FHB) and maize stalk rot (MSR), caused by members of the Fusarium graminearum species complex (FGSC), are among the most destructive and economically important diseases in the world. Species identity and the trichothecene chemotype of 312 members of the FGSC from diseased wheat spikes and maize stalks in Henan was determined using phylogenetic analyses and a polymerase chain reaction trichothecene chemotype assay. F. graminearum sensu stricto accounted for more than 93% of the FGSC isolates associated with FHB (N = 168) and MSR (N = 130). The remaining isolates were F. asiaticum. Significant differences were found in the frequencies of the two species within the hosts (P < 0.01). However, the frequencies of the same species in FHB and MSR were similar (P > 0.05) for wheat and maize isolates, indicating that the composition of the FGSC with respect to wheat and maize in these fields varied little. The 15-acetyl-deoxynivalenol (15-ADON) trichothecene chemotype represented 92.7 and 98.5% of isolates from wheat (N = 167) and maize (N = 130), respectively. However, the 3-acetyl-deoxynivalenol chemotype was found in 6.7% of wheat isolates, and the nivalenol chemotype in 1.5% of MSR isolates and in 0.6% of FHB isolates. Mycelial growth at different concentrations of carbendazim and difenoconazole did not differ between F. graminearum sensu stricto and F. asiaticum. These results suggest that the 15-ADON chemotype of F. graminearum sensu stricto is the predominant pathogen that causes wheat- and maize-related diseases in this region. Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Fitness of three chemotypes of Fusarium graminearum species complex in major winter wheat-producing areas of China

In China, Fusarium head blight is caused mainly by the Fusarium graminearum species complex (FGSC), which produces trichothecene toxins. The FGSC is divided into three chemotypes: 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), and nivalenol (NIV). In order to predict the geographical changes in the distribution of these chemotype populations in major winter wheat-producing areas in China, the biological characteristics of twenty randomly selected isolates from each of the three chemotypes were studied. No significant difference was exhibited in the growth rate of 3-ADON, 15-ADON, and NIV isolates at 15°C. At 20°C and 25°C, the growth rate of 15-ADON isolates was the highest. At 30°C, the growth rate of NIV and 3-ADON isolates was significantly higher than that of 15-ADON isolates. The 15-ADON isolates produced the highest quantities of perithecia and two to three days earlier than the other two populations at each temperature, and released more ascospores at 18°C. The aggressiveness test on wheat seedlings and ears indicated there was no significant difference between the 3-ADON and 15-ADON isolates. However, the aggressiveness of NIV isolates was significantly lower than that of the 3-ADON and 15-ADON isolates. The DON content in grains from heads inoculated with the 3-ADON isolates was higher than the content of 15-ADON and NIV isolates. The results showed that 15-ADON population had the advantage in perithecia formation and ascospore release, and the 3-ADON population produced more DON in wheat grains. We suggested that distribution of these three chemotype populations may be related to these biological characteristics.

Fusarium graminearum pyruvate dehydrogenase kinase 1 (FgPDK1) Is Critical for Conidiation, Mycelium Growth, and Pathogenicity

Pyruvate dehydrogenase kinase (PDK) is an important mitochondrial enzyme that blocks the production of acetyl-CoA by selectively inhibiting the activity of pyruvate dehydrogenase (PDH) through phosphorylation. PDK is an effectively therapeutic target in cancer cells, but the physiological roles of PDK in phytopathogens are largely unknown. To address these gaps, a PDK gene (FgPDK1) was isolated from Fusarium graminearum that is an economically important pathogen infecting cereals. The deletion of FgPDK1 in F. graminearum resulted in the increase in PDH activity, coinciding with several phenotypic defects, such as growth retardation, failure in perithecia and conidia production, and increase in pigment formation. The ΔFgPDK1 mutants showed enhanced sensitivity to osmotic stress and cell membrane-damaging agent. Physiological detection indicated that reactive oxygen species (ROS) accumulation and plasma membrane damage (indicated by PI staining, lipid peroxidation, and electrolyte leakage) occurred in ΔFgPDK1 mutants. The deletion of FgPDK1 also prohibited the production of deoxynivalenol (DON) and pathogenicity of F. graminearum, which may resulted from the decrease in the expression of Tri6. Taken together, this study firstly identified the vital roles of FgPDK1 in the development of phytopathogen F. graminearum, which may provide a potentially novel clue for target-directed development of agricultural fungicides.

Survey of Fusarium spp. Causing Wheat Crown Rot in Major Winter Wheat Growing Regions of China

Fusarium crown rot of wheat has become more prevalent in China. To investigate the phylogenetic structure of Fusarium causing wheat crown rot in China, wheat basal stems with symptoms of the disease were collected from 2009 to 2013 in Jiangsu, Anhui, Henan, Hebei, and Shandong provinces. In total, 175 Fusarium isolates were collected and their mycotoxin chemotypes and distribution were identified. Among the 175 isolates, 123 were Fusarium asiaticum; 95 of these were the chemotype 3-acetyl-deoxynivalenol (3-AcDON) and 28 were nivalenol (NIV). Thirty-seven isolates belonged to F. graminearum, which were all 15-AcDON. Smaller numbers of isolates consisted of F. acuminatum, F. pseudograminearum, and F. avenaceum. The virulence of F. asiaticum and F. graminearum isolates on wheat crowns and heads was comparable. The virulence of isolates of the DON and NIV chemotype were statistically similar, but DON tended to be more aggressive. The DON concentrations in grains from wheat heads inoculated with isolates causing either Fusarium head blight or crown rot were similar. In the five provinces, F. asiaticum of the 3-AcDON chemotype was the predominant pathogen causing crown rot, followed by F. graminearum. Recent changes in causal Fusarium species, chemotypes, and distribution in China are discussed.

Genetic relationships, carbendazim sensitivity and mycotoxin production of the Fusarium graminearum populations from maize, wheat and rice in eastern China

Members of the Fusarium graminearum species complex (FGSC) are important pathogens on wheat, maize, barley, and rice in China. Harvested grains are often contaminated by mycotoxins, such as the trichothecene nivalenol (NIV) and deoxynivalenol (DON) and the estrogenic mycotoxin zearalenone (ZEN), which is a big threat to humans and animals. In this study, 97 isolates were collected from maize, wheat, and rice in Jiangsu and Anhui provinces in 2013 and characterized by species- and chemotype-specific PCR. F. graminearum sensu stricto (s. str.) was predominant on maize, while most of the isolates collected from rice and wheat were identified as F. asiaticum. Fusarium isolates from three hosts varied in trichothecene chemotypes. The 3-acetyldeoxynivalenol (3ADON) chemotype predominated on wheat and rice population, while 15ADON was prevailing in the remaining isolates. Sequence analysis of the translation elongation factor 1α and trichodiene synthase indicated the accuracy of the above conclusion. Additionally, phylogenetic analysis suggested four groups with strong correlation with species, chemotype, and host. These isolates were also evaluated for their sensitivity to carbendazim and mycotoxins production. The maize population was less sensitive than the other two. The DON levels were similar in three populations, while those isolates on maize produced more ZEN. More DON was produced in carbendazim resistant strains than sensitive ones, but it seemed that carbendazim resistance had no effect on ZEN production in wheat culture.