山东省小麦赤霉病菌种群组成及其致病力分化

由禾谷镰孢菌群Fusarium graminearum clade引起的赤霉病是小麦的重要病害。为明确山东省小麦赤霉病菌的种群组成及其致病力,于2011年和2012年从山东省15地市分离了95株小麦赤霉病菌,在形态和分子生物学鉴定种的基础上,采用鉴定B型毒素化学型的特异性引物进行毒素化学型分析。在95个菌株中,93株分离物为禾谷镰孢菌F.graminearum,2株为燕麦镰孢菌F.avenaceum。94株分离物为脱氧雪腐镰孢菌烯醇(deoxynivalenol,DON)化学型,1株为雪腐镰孢菌烯醇(nivalenol,NIV)化学型。在94株DON毒素化学型菌株中,90株为15-乙酰脱氧雪腐镰孢菌烯醇(15-acetyldeoxynivalenol,15-AcDON)化学型,4株为3-乙酰脱氧雪腐镰孢菌烯醇(3-acetyldeoxynivalenol,3-AcDON)化学型。在小麦扬花期,采用单花滴注接种法对29个菌株进行了致病力测定,供试菌株的致病力分化明显。表明在山东省冬小麦产区,产15-AcDON毒素的F.gra-minearum是小麦赤霉病菌的优势种群。     

Nivalenol‐producing Fusarium cerealis associated with fusarium head blight in winter wheat in Manitoba,Canada

Fusarium head blight (FHB) in small grain cereals is primarily caused by the members of the Fusarium graminearum species complex. These produce mycotoxins in infected grains, primarily deoxynivalenol (DON); acetylated derivatives of DON, 3‐acetyl‐DON (3‐ADON) and 15‐acetyl‐DON (15‐ADON); and nivalenol (NIV). This study reports the isolation of Fusarium cerealis in infected winter wheat heads for the first time in Canada. A phylogenetic analysis based on the TRI101 gene and F. graminearum species‐specific primers revealed two species of Fusarium: F. graminearum sensu stricto (127 isolates) and F. cerealis (five isolates). Chemotype determination based on the TRI3 gene revealed that 65% of the isolates were 3‐ADON, 31% were 15‐ADON and 4% were NIV producers. All the F. cerealis isolates were of NIV chemotype. Fusarium cerealis isolates can often be misidentified as F. graminearum as the morphological characteristics are similar. Although the cultural and macroconidial characteristics of F. graminearum and F. cerealis isolates were similar, the aggressiveness of these isolates on susceptible wheat cultivar Roblin and moderately resistant cultivar Carberry differed significantly. The F. graminearum 3‐ADON isolates were most aggressive, followed by F. graminearum 15‐ADON and F. cerealis NIV isolates. The findings from this study confirm the continuous shift of chemotypes from 15‐ADON to 3‐ADON in North America. In Canada, the presence of NIV is limited to barley samples and the discovery of NIV‐producing F. cerealis species in Canadian wheat fields may pose a serious concern to the Canadian wheat industry in the future.     

Genetic Variability of Central European Isolates of the <Emphasis Type="Italic">Fusarium graminearum</Emphasis> Species Complex

The main causative agents of Fusarium head blight in central Europe are Fusarium graminearum and F. culmorum. We examined the mycotoxin producing ability, aggressiveness and molecular variability of F. graminearum isolates. Altogether twenty-six Hungarian, three Austrian isolates and representatives of eight species identified in the F. graminearum species complex were involved in this study. Mycotoxin producing abilities of the isolates were tested by GC-MS and HPLC. The central European isolates were found to belong to chemotype I (producing deoxynivalenol). Most isolates produced more 15-acetyl-deoxynivalenol than 3-acetyl-deoxynivalenol suggesting that they belong to chemotype Ib. All F. graminearum isolates were found to be highly pathogenic in in vitro aggressiveness tests. Phylogenetic analysis of random amplified polymorphic DNA profiles, and restriction profiles of the intergenic spacer region of the ribosomal RNA gene cluster of the isolates allowed clustering of the central European isolates into 17 and 16 haplotypes, respectively. When RAPD and IGS-RFLP data were combined, almost every single central European F. graminearum isolate could be differentiated (27/29 haplotypes). Sequence analysis of a putative reductase gene of some isolates was also performed. Based on molecular data, the majority of the central European isolates belonged to F. graminearum sensu stricto characteristic to the northern hemisphere, with the exception of one Hungarian isolate, which was not related to any known species of the F. graminearum species complex based on sequence data. The taxonomic assignment of two other Hungarian isolates, previously suggested as belonging to F. boothii based on mitochondrial DNA restriction profiles, was supported by sequence analysis.     

A comparison of aggressiveness and deoxynivalenol production between Canadian <Emphasis Type="Italic">Fusarium graminearum</Emphasis> isolates with 3-acetyl and 15-acetyldeoxynivalenol chemotypes in field-grown spring wheat

Twenty four isolates of Fusarium graminearum, half of which were 3-acetyldeoxynivalenol (3-ADON) and half 15-acetyldeoxynivalenol (15-ADON) chemotypes, were tested for their ability to produce deoxynivalenol and to cause Fusarium head blight (FHB) in spring wheat cultivars. The objectives of this study were to determine (1) whether 3-ADON isolates differ in aggressiveness, as measured by the FHB index, and DON production from 15-ADON isolates under field conditions, and (2) whether the performance of resistant host cultivars was stable across isolates. Field tests of all isolates were conducted with three replicates at each of two locations in Canada and Germany in 2008 with three host genotypes differing in FHB resistance level. The resistant host genotype showed resistance regardless of the chemotype or location. The differences between mean FHB indices of 3-ADON and 15-ADON isolates were not significant for any wheat genotype. In contrast, average DON production by the 3-ADON isolates (10.44 mg kg⁻¹) was significantly (P < 0.05) higher than for the 15-ADON isolates (6.95 mg kg⁻¹) at three of the four locations where moderately resistant lines were tested, and at both locations where susceptible lines were evaluated. These results indicate that 3-ADON isolates could pose a greater risk to food safety. However, as the mean aggressiveness and DON production of 3-ADON and 15-ADON chemotypes was similar on highly resistant lines, breeding and use of highly resistant lines is still the most effective measure of reducing the risks associated with DON in wheat.     

Molecular characterization of the Fusarium graminearum species complex in Eastern China

Members of the Fusarium graminearum species complex (FGSC) cause Fusarium head blight in small cereal grains all over the world. To determine the species and trichothecene chemotype composition and population structure of FGSC in Jiangsu and Anhui provinces, an area where epidemics occur regularly, 891 isolates were collected in two consecutive years (2011 and 2012) and characterized with species- and chemotype-specific polymerase chain reaction. Of the 891 isolates typed, 83 were F. graminearum sensu stricto (s. str.) and 808 were F. asiaticum. All 83 F. graminearum s. str. isolates were of a 3ADON (26.51 %) or 15ADON (73.49 %) type, while F. asiaticum isolates included 696 3ADON producers, 46 15ADON producers, and 66 NIV producers. Eight variable number tandem repeat (VNTR) markers were tested on a representative 384 F. asiaticum isolates from 55 sampling sites. VNTR analysis showed high gene diversity and genotypic diversity but low linkage disequilibrium in both populations Fg2011 and Fg2012 grouped based on the year of collection. Low genetic differentiation (F _ST ? =?0.026) and high gene flow (N _m ?=?15.13) was observed between the two populations and among subpopulations within the same population (N _m ?=?3.53 to 48.37), indicating that few influence of temporal and spatial variations on population differentiation in this area. Similar result was obtained from 3ADON, 15ADON and NIV populations or carbendazim resistant and sensitive populations, indicating that chemotype of Fusarium isolates and carbendazim application had minor influence on population subdivision.     

Vegetative Compatibility and Mycotoxin Chemotypes among Fusarium graminearum (Gibberella zeae) Isolates from Wheat in Argentina

Gibberella zeae (anamorph Fusarium graminearum) is the main pathogen causing Fusarium head blight of wheat in Argentina. The objective of this study was to determine the vegetative compatibility groups (VCGs) and mycotoxin production (deoxynivalenol, nivalenol and 3-acetyl deoxynivalenol) by F. graminearum populations isolated from wheat in Argentina. VCGs were determined among 70 strains of F. graminearum isolated from three localities in Argentina, using nitrate non-utilizing (nit) mutants. Out of 367 nit mutants generated, 41% utilized both nitrite and hypoxanthine (nit1), 45% utilized hypoxanthine but not nitrite (nit3), 9% utilized nitrite but not hypoxanthine (NitM) and 5% utilized all the nitrogen sources (crn). The complementations were done by pairing the mutants on nitrate medium. Fifty-five different VCGs were identified and the overall VCG diversity (number of VCGs/number of isolates) averaged over the three locations was 0.78. Forty-eight strains were incompatible with all others, thus each of these strains constituted a unique VCG. Twenty-two strains were compatible with other isolates and were grouped in seven multimembers VCGs. Considering each population separately, the VCG diversity was 0.84, 0.81 and 1.0 for San Antonio de Areco, Alberti and Marcos Juarez, respectively. Toxin analysis revealed that of the 70 strains of F. graminearum tested, only 90% produced deoxynivalenol, 10% were able to produce deoxynivalenol and very low amounts of 3-acetyldeoxynivalenol. No isolate produced nivalenol. The results indicate a high degree of VCG diversity in the F. graminearum populations from wheat in Argentina. This diversity should be considered when screening wheat germplasm for Fusarium head blight resistance.     

Natural occurrence of fusarium head blight,mycotoxins and mycotoxin‐producing isolates of Fusarium in commercial fields of wheat in Hubei

Combined analyses of the natural occurrence of fusarium head blight (FHB), mycotoxins and mycotoxin‐producing isolates of Fusarium spp. in fields of wheat revealed FHB epidemics in 12 of 14 regions in Hubei in 2009. Mycotoxin contamination ranged from 0·59 to 15·28 μg g^?1 in grains. Of the causal agents associated with symptoms of FHB, 84% were Fusarium asiaticum and 9·5% were Fusarium graminearum, while the remaining 6·5% were other Fusarium species. Genetic chemotyping demonstrated that F. asiaticum comprised deoxynivalenol (DON), 3‐acetyldeoxynivalenol (3‐AcDON), 15‐acetyldeoxynivalenol (15‐AcDON) and nivalenol (NIV) producers, whereas F. graminearum only included DON and 15‐AcDON producers. Compared with the chemotype patterns in 1999, there appeared to be a modest shift towards 3‐AcDON chemotypes in field populations during the following decade. However, isolates genetically chemotyped as 3‐AcDON were present in all regions, whereas the chemical 3‐AcDON was only detected in three of the 14 regions where 3‐AcDON accounted for 15–20% of the DON and acetylated forms. NIV mycotoxins were detected in seven regions, six of which also yielded NIV chemotypes. The number of genetic 3‐AcDON producers was positively correlated with amounts of total mycotoxins (DON, NIV and acetylated forms) or DON in wheat grains. Chemical analyses of wheat grains and rice cultures inoculated with different isolates from the fields confirmed their genetic chemotypes and revealed a preferential biosynthesis of 3‐AcDON and 4‐AcNIV in rice. These findings suggest the importance of chemotyping coupled with species identification for improved prediction of mycotoxin contamination in wheat.     

Variation in Pathogenicity Associated with the Genetic Diversity of Fusarium graminearum

We screened 188 isolates of Fusarium graminearum, which originated from northwest Europe, the USA and Nepal, for genetic diversity using a sequence-characterised amplified region polymorphism (SCAR). On the basis of this analysis, 42 of the 118 isolates were selected for random amplified polymorphic DNA (RAPD) analysis. Three groups were identified, two of which, A and B, contained the isolates from Nepal, and a third, group C, contained the isolates from Europe and the USA. In pathogenicity tests on wheat and maize seedlings, group C isolates were more pathogenic than the group A and B isolates. The isolates were assigned chemotypes based on their ability to produce the trichothecene mycotoxins nivalenol (NIV) and deoxynivalenol (DON). Isolates from group A were equally likely to produce NIV or DON while group B isolates produced predominantly NIV, and group C isolates produced predominantly DON. Within group A, isolates of the two chemotypes were equally pathogenic to wheat but isolates with the NIV chemotype were significantly more pathogenic to maize. The results confirm that distinct genetic groups exist within F. graminearum and demonstrate that these groups have different biological properties, especially with respect to their pathogenicity to two of the most economically important hosts of this pathogen.     

Diversity of the Fusarium graminearum species complex on French cereals

Fusarium graminearum is an important pathogen causing Fusarium head blight (FHB) on wheat and barley and Fusarium ear rot (FER) on maize, and harvested grains often are contaminated with trichothecenes such as deoxynivalenol (DON) and nivalenol (NIV) that are a major health and food safety concern due to their toxicity to humans and farm animals. In this study, species identity and trichothecene toxin potential of 294 members of the Fusarium graminearum species complex (FGSC) collected from wheat, barley and maize in France in 2011 was determined using a microsphere-based multilocus genotyping assay. F. graminearum was predominant on all three hosts, but three isolates of F. cortaderiae and two isolates representing F. graminearum × F. boothii hybrids were also identified from maize. The 15-ADON trichothecene chemotype predominated on all three hosts, representing 94.7 %, 87.8 % and 85.4 % of the strains on barley (N?=?19), wheat (N?=?90), and maize (N?=?185), respectively. However, the NIV chemotype was found in 12.2 % of the wheat isolates and in 14.6 % of the maize isolates. Only a single FGSC isolate from this study, originating from barley, was found to have the 3-ADON chemotype. Regional differences could be observed in the distribution of the 15-ADON and NIV chemotypes, with the NIV producing-isolates being present at higher frequency (21.2 %) in the South of France compared to the rest of the country (4.4 %). Such information is critical because of the increased concern associated with NIV contamination of cereals. In addition, these results are needed to develop management strategies for FHB and FER in France and to improve understanding of the distribution and significance of FGSC diversity in Europe and worldwide.     

Genetic variation of aggressiveness in individual field populations ofFusarium graminearum andFusarium culmorum tested on young plants of winter rye

Fusarium graminearum andF. culmorum are capable of infecting winter cereals at all growth stages. From natural field epidemics of wheat head blight and rye foot rot, three fungal populations were collected with 21, 38 and 54 isolates, respectively; their aggressiveness was analyzed in comparison to collections ofF. graminearum (25 isolates) andF. culmorum (70 isolates) that represent a wide range of geographical locations and host species. All isolates were tested for aggressiveness on young plants of winter rye in the greenhouse and scored for disease severity on a 1–9 scale. Disease ratings of individual isolates ranged from 1.5 to 5.7 indicating quantitative variation of aggressiveness. Genotypic variance was highest in the twoFusarium collections. No substantial difference was found in the amount of genotypic variation betweenF. graminearum andF. culmorum. Individual field populations revealed 57–66% of the total genotypic variation of the collections. This implies a high degree of diversity of aggressiveness within single field populations ofF. graminearum andF. culmorum causing natural epidemics.     

Characterization of Fusarium asiaticum and F. graminearum isolates from gramineous weeds in the proximity of rice fields in Korea

Fusarium graminearum species complexes (FGSCs), such as Fusarium asiaticum and F. graminearum, are important pathogens that cause Fusarium head blight (FHB) in several cereal crops worldwide. In this study, we collected 342 gramineous weed samples in the proximity of rice fields from May to June 2018 in Korea. Among the 500 Fusarium isolates from the weed samples, 13 species of Fusarium were identified, and F. asiaticum (41.2%), F. avenaceum (18.0%), F. acuminatum (16.4%) and F. graminearum (14.8%) were the most frequently isolated. The trichothecene genotype analysis showed that 206 F. asiaticum strains consisted of the nivalenol (NIV) genotype (n = 195, 94.7%) and 3-acetyldeoxynivalenol (3ADON) genotype (n = 11, 5.3%), whereas 74 F. graminearum strains consisted of the 15-acetyldeoxynivalenol (15ADON) genotype (n = 58, 78.4%) and 3ADON genotype (n = 16, 21.6%). Geographical differences were observed in the FGSC and trichothecene genotype compositions, which appeared host-dependent between the southern provinces and mid-eastern provinces. The aggressiveness assessment of FHB showed that the 3ADON chemotype was most aggressive followed by the 15ADON and NIV chemotypes in wheat, while the NIV chemotype was most aggressive followed by the 3ADON and 15ADON chemotypes in rice. The F. asiaticum strains grew slowly and produced fewer conidia and perithecia than the F. graminearum strains, regardless of their chemotypes. The results of this study suggest that F. asiaticum with the NIV chemotype has a host preference for rice, and FHB-causing pathogens can be harboured in gramineous weeds, which play a role in the dispersal of FHB pathogens to rice and other cereal crops.     

Comparison of genetic diversity and pathogenicity of fusarium head blight pathogens from China and Europe by SSCP and seedling assays on wheat

The genetic diversity and pathogenicity of isolates of Fusarium graminearum and F. asiaticum isolated from wheat heads in China were examined and compared with those of isolates of F. graminearum , F. asiaticum and F. meridionale from Europe, USA and Nepal. Genetic diversity was assessed by SSCP (single strand conformation polymorphism) and AFLP (amplified fragment length polymorphism) analysis and by molecular chemotyping. SSCP analysis of the Fg16F/Fg16R PCR amplicon differentiated F. graminearum , F. asiaticum and F. meridionale and revealed three haplotypes among sequence-characterized amplified region (SCAR) type 1 F. graminearum isolates. AFLP analysis showed a high level of genetic diversity and clustered the majority of Chinese isolates in one group along with other isolates of Asian origin. The second cluster contained F. graminearum isolates from China, Europe and the USA. Of the Chinese isolates, 79% were F. asiaticum and 81% of these were of the 3-AcDON chemotype, with only 9·5% of either chemotype 15-AcDON or NIV. All the Chinese and USA isolates of F. graminearum were 15-AcDON, whereas among the isolates from Europe, 21% were NIV and 8% were 3-AcDON chemotype. No evidence was found for possible differences in aggressiveness between F. graminearum and F. asiaticum . Highly aggressive isolates were present in each region and no evidence was found for any association between aggressiveness and geographical origin or chemotype among the isolates examined. No difference was observed in pathogenicity towards wheat seedlings between Chinese isolates and those from Europe, the USA or Nepal.     

Trichothecene genotype and genetic variability of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> and <Emphasis Type="Italic">F. cerealis</Emphasis> isolated from durum wheat in Argentina

Fusarium head blight (FHB) is one of the most important fungal diseases affecting wheat worldwide and it is caused mainly by species within the Fusarium graminearum species complex (FGSC). This study evaluated the presence of FGSC in durum wheat from the main growing area in Argentina and analyzed the trichothecene genotype and chemotype of the strains isolated. Also, the genetic variability of the strains was assayed using ISSR markers. Molecular analysis revealed that among the strains isolated and identified morphologically as F. graminearum, there were 14 strains identified as F. cerealis. Also, it revealed that durum wheat grains were mostly contaminated by F. graminearum, being this the only species reported so far, within the FGSC, affecting durum wheat in Argentina. Analysis of molecular variance (AMOVA) indicated a high genetic variability within rather than between F. graminearum populations. All F. graminearum strains presented 15ADON genotype and were able to produce DON while all F. cerealis strains presented the NIV genotype and most of them were able to produce this toxin. The finding of F. cerealis in durum wheat grains indicates the need for investigating if this fungus is the responsible for the NIV contamination found in wheat in Argentina.     

Phenotypic and pathogenic traits of two species of the Fusarium graminearum complex possessing either 15-ADON or NIV genotype

Fusarium head blight (FHB) in Brazil is caused mainly by two members of the Fusarium graminearum species complex, each possessing either a DON/15-ADON chemotype (F. graminearum sensu stricto, Fgss) or a NIV chemotype (F. meridionale, Fmer). In this work, we aimed to characterize and compare isolates belonging to each species, obtained either from wheat or barley, in relation to phenotypic traits (mycelial growth, sporulation and germination) and pathogenicity (in vitro glume infection and in vivo central floret inoculation) to two Brazilian wheat cultivars, Guamirim (moderate susceptible) and BRS 194 (susceptible). Results showed significantly higher growth rates, greater spore production and quicker germination for the Fgss isolates compared to the Fmer isolates, which were also more sensitivity to tebuconazole than the Fgss isolates. All isolates were capable of infecting glume tissues of both varieties, with an overall higher infection frequency for Fgss than Fmer isolates when inoculated in cv. Guamirim than in cv. BRS194, which showed similar infection frequency between the species. Accordingly, in the central-floret inoculation assay, Fgss isolates were also more aggressive than Fmer isolates towards cv. Guamirim, but not towards BRS194, based on the mean area under disease progress curves. It is hypothesized that phenotypic traits and host resistance may play a role in the selection of more aggressive populations under field conditions, thus partially explaining the dominance of Fgss populations associated with FHB of wheat in Brazil.     

Morphological and molecular identification of <Emphasis Type="Italic">Fusarium</Emphasis> species associated with head blight on wheat in East Croatia

Fusarium head blight (FHB) is an important fungal disease of wheat. The aim of this research was to determine the diversity of Fusarium species infecting winter wheat ears in East Croatia. In 2008 wheat kernels were obtained from three locations in the eastern part of Croatia (Tovarnik, Osijek, Pozega), and in 2009 from two additional locations (Slavonski Brod, Nova Gradiska). In total, 498 visually diseased kernels were selected for morphological identification of Fusarium spp. The identity of 226 selected isolates was further investigated by molecular techniques. The predominant species on wheat kernels in East Croatia in 2008 were F. graminearum, isolated and confirmed from more than 80% of sampled wheat kernels, followed by F. avenaceum (8%) and F. culmorum (7%). Incidence of F. poae was less than 2%. The most common species identified in 2009 were F. graminearum (50%), F. culmorum (13%), F. avenaceum (12%) and F. poae (7%). This is the first report on the identification of Fusarium species isolated from naturally infected wheat ears in Croatia.     

Head-blighting populations of Fusarium culmorum from Germany, Russia, and Syria analyzed by microsatellite markers show a recombining structure

Fusarium culmorum is a haploid, worldwide occurring phytopathogenic fungus causing seedling blight, foot rot, and head blight of cereals and producing the mycotoxins deoxynivalenol (DON) and nivalenol (NIV) associated with health hazards in human and animals. The fungus reproduces asexually by conidiospores, a teleomorph is not known. We analyzed for the first time naturally occurring F. culmorum populations collected randomly in the field from infected wheat heads. A total of 186 isolates, from three populations from Germany (GER), Russia (RUS), Syria (SYR), as well as an international collection (INT) for comparison, were genotyped by 10 microsatellite (SSR, single sequence repeat) markers. A high genetic diversity within the three natural populations and the INT population as well was detected. About 90 % of multi-locus haplotypes (MLH) were unique across populations. The largest part of variance (81 %) was found within populations. Accordingly, population subdivision was low, fixation indices were significant only in one out of six comparisons, while estimates of gene flow (N _m ) ranged from 0.8–4.8. Linkage equilibrium was revealed by the index of multi-locus association and the quotient of observed and expected variance when two linked markers were deleted. DON and NIV chemotypes grouped closely together in a principle coordinate analysis. SYR isolates were partly separated from GER and RUS populations. All population-genetic parameters were in a similar range compared to those for the sexually propagating species F. graminearum. In conclusion, results support the hypothesis of a recombining structure in F. culmorum as revealed by the high genetic variation within populations, a low fixation index and low gametic phase disequilibrium within populations.     

Comparative population structure and trichothecene mycotoxin profiling of Fusarium graminearum from corn and wheat in Ontario,central Canada

Fusarium graminearum causes fusarium head blight (FHB) of wheat and gibberella ear rot (GER) of corn in Canada and also contaminates grains with trichothecene mycotoxins. Very little is known about trichothecene diversity and population structure of the fungus from corn in Ontario, central Canada. Trichothecene genotypes of F. graminearum isolated from corn (n = 452) and wheat (n = 110) from 2010 to 2012 were identified. All the isolates were deoxynivalenol (DON) type. About 96% of corn isolates and 98% of wheat isolates were 15‐acetyl deoxynivalenol (15ADON) type. The fungal population structures from corn (n = 313) and wheat (n = 73) were compared using 10 variable number tandem repeat (VNTR) markers. The fungal populations and subpopulations categorized based on host, cultivar groups, years and geography showed high gene (H = 0.818–0.928) and genotypic (GD = 0.999–1.00) diversity. Gene flow was also high between corn and wheat population pairs (Nm = 8.212), and subpopulation pairs within corn (Nm = 7.13–23.614) or wheat (Nm = 19.483) populations. Phylogenetic analysis revealed that isolates from both hosts were F. graminearum clade 7. These findings provide baseline data on 3‐acetyl deoxynivalenol (3ADON) and 15ADON profiles of F. graminearum isolates from corn in Canada and are useful in evaluating mycotoxin contamination risks in corn and wheat grains. Understanding the fungal genetic structure will assist evaluation and development of resistant cultivars/germplasm for FHB on wheat and GER on corn.     

ISSR markers detect high genetic variation among <Emphasis Type="Italic">Fusarium poae</Emphasis> isolates from Argentina and England

Fusarium poae is one of the Fusarium species isolated from cereal grains infected by Fusarium head blight (FHB), and in recent years it has been identified as a major FHB component. In this study, 97 F. poae isolates from Argentina (n = 62) and England (n = 35) were analysed by inter-simple sequence repeats (ISSR) to examine the genetic diversity and to determine whether intraspecific variation could be correlated with geographic and/or host origin. The molecular analysis showed high intraspecific variability within F. poae isolates, but did not reveal a clear relationship between variability and the host/geographic origin. Fusarium poae isolates from the same geographic region or host appeared in different subclusters. Conversely, isolates with the same haplotype were also collected from different geographic regions. However, we did observe subclusters consisting of isolates from Argentina only or from England only. Furthermore, a single seed sample was found to host different haplotypes. Analysis of molecular variance (AMOVA) indicated a high genetic variability in F. poae, with most of the genetic variability explained by differences within, rather than between Argentinean and English populations. This is the first report on genetic diversity of F. poae using ISSR markers. Moreover, ISSR fingerprinting generates highly polymorphic markers for F. poae and proved to be a useful and reliable assay for genetic variability studies.     

Fusarium pseudograminearum as an emerging pathogen of crown rot of wheat in eastern China

Fusarium crown rot of wheat has been spreading in the Huanghuai wheat-growing area in China since 2010, leading to a potential yield loss. To investigate the pathogens associated with this disease in Jiangsu and Shandong provinces in recent years, 617 Fusarium isolates were isolated from nine sites in these two provinces between 2014 and 2016. Of these isolates, 372 were identified as Fusarium pseudograminearum, and the remaining isolates were identified as F. asiaticum and F. graminearum, suggesting that F. pseudograminearum is becoming a predominant causative pathogen of crown rot of wheat in eastern China. Trichothecene gene detection and chemical analyses of trichothecenes indicated that the F. pseudograminearum isolates belonged to the 3-ADON or 15-ADON chemotype, and one isolate had the NIV genotype but produced no detectable NIV. 3-ADON isolates were predominant in Jiangsu, whereas 15-ADON isolates were prevalent in Shandong. The mating type of the F. pseudograminearum isolates were identified. MAT-1 and MAT-2 existed, but in most collections, particularly those in Jiangsu, the ratios of the two mating types deviated significantly from an expected 1:1 ratio. The reason for the occurrence of F. pseudograminearum is hypothesized, and the chemotype and mating type distribution of this species in these two provinces are analysed.     

Genetic Diversity of Fusarium Graminearum in Europe and Asia

The biodiversity and phylogeny of Fusarium graminearum isolates originating from different geographical areas was analyzed using isozyme variation, β-tubulin and IGS sequences. Geographically distinct groups of isolates originating from different areas of the Russian Federation, China, Germany and Finland were studied. The complex enzymes (α- and β-esterases, aspartate aminotransferase and superoxide dismutase) and the IGS sequences demonstrated a high level of genetic diversity in F. graminearum. Diversity in the Asian population was higher than in the European one. There was a correlation between genetic clusters of the IGS sequences and geographical origin in F. graminearum. Knowledge of biodiversity and identification of some phylogenetic lineages in F. graminearum will be useful in defining the risk of pathogen evolution as well as benefiting disease management strategies.