Real-time PCR Quantification and Mycotoxin Production of Fusarium graminearum in Wheat Inoculated with Isolates Collected from Potato, Sugar Beet, and Wheat

ABSTRACT Fusarium graminearum causes Fusarium head blight (FHB) in small grains worldwide. Although primarily a pathogen of cereals, it also can infect noncereal crops such as potato and sugar beet in the United States. We used a real-time polymerase chain reaction (PCR) method based on intergenic sequences specific to the trichodiene synthase gene (Tri5) from F. graminearum. TaqMan probe and primers were designed and used to estimate DNA content of the pathogen (FgDNA) in the susceptible wheat cv. Grandin after inoculation with the 21 isolates of F. graminearum collected from potato, sugar beet, and wheat. The presence of nine mycotoxins was analyzed in the inoculated wheat heads by gas chromatography and mass spectrometry. All isolates contained the Tri5 gene and were virulent to cv. Grandin. Isolates of F. graminearum differed significantly in virulence (expressed as disease severity), FgDNA content, and mycotoxin accumulation. Potato isolates showed greater variability in producing different mycotoxins than sugar beet and wheat isolates. Correlation analysis showed a significant (P < 0.001) positive relationship between FgDNA content and FHB severity or deoxynivalenol (DON) production. Moreover, a significant (P < 0.001) positive correlation between FHB severity and DON content was observed. Our findings revealed that F. graminearum causing potato dry rot and sugar beet decay could be potential sources of inoculum for FHB epidemics in wheat. Real-time PCR assay provides sensitive and accurate quantification of F. graminearum in wheat and can be useful for monitoring the colonization of wheat grains by F. graminearum in controlled environments, and evaluating wheat germplasms for resistance to FHB.     

脱氧雪腐镰刀菌烯醇( DON) 在小麦籽粒中的积累分析

 镰刀菌产生的脱氧雪腐镰刀菌烯醇(deoxynivalenol,DON)污染小麦后对人畜具有较大的毒害作用。为明确DON毒素在小麦籽粒中的积累数量及其与镰刀菌菌株、接菌数量、小麦品种和病害严重度的关系,试验采用单花滴注方法在5个抗病性不同的小麦品种上分别接种9 个禾谷镰刀菌菌株,每个菌株接种1 × 106 、1 × 105 和1 × 104 个/ mL 3 个分生孢子浓度,并利用ELISA 法测定收获麦粒中DON 毒素含量。结果表明,麦粒中DON 毒素含量差异主要是由于不同禾谷镰刀菌菌株产生毒素能力不同所致。接种菌株8003、4020 的所有麦粒中DON 毒素含量均显著高于相同条件下接种其他7 个菌株的小麦。当接种产毒素能力强的菌株时,小麦抗病品种表现出在一定程度上降低DON 毒素积累的能力。不同接菌浓度对小麦赤霉病的发病程度和麦粒中DON 毒素含量有显著影响,在相同条件下,接菌浓度越高,病害严重度越高,DON 毒素含量也越高;反之,接菌浓度越低,病害严重度越低,DON 毒素含量也越低。     

Geographic distribution and genetic diversity of Fusarium graminearum and F. asiaticum on wheat spikes throughout China

A large number of Fusarium graminearum and F. asiaticum isolates were collected from wheat spikes from all regions in China with a history of fusarium head blight (FHB) epidemics. Isolates were analysed to investigate their genetic diversity and geographic distribution. Sequence characterized amplified region (SCAR) analyses of 437 isolates resolved both species, with 21% being F. graminearum (SCAR type 1) and 79% being F. asiaticum (SCAR type 5). AFLP profiles clearly resolved two groups, A and B, that were completely congruent with both species. However, more diversity was detected by AFLP, revealing several subgroups within each group. In many cases, even for isolates from the same district, AFLP haplotypes differed markedly. Phylogenetic analyses of multilocus DNA sequence data indicated that all isolates of SCAR type 1, AFLP group A were F. graminearum , whilst isolates of SCAR type 5, AFLP group B were F. asiaticum , demonstrating that it is an efficient method for differentiating these two species. Both species seem to have different geographic distributions within China. Fusarium graminearum was mainly obtained from wheat growing in the cooler regions where the annual average temperature was 15°C or lower. In contrast, the vast majority of F. asiaticum isolates were collected from wheat growing in the warmer regions where the annual average temperature is above 15°C and where FHB epidemics occur most frequently. This is the first report of the distribution of, and genetic diversity within, F. graminearum and F. asiaticum on wheat spikes throughout China.     

Evaluation of type I fusarium head blight resistance of wheat using non-deoxynivalenol-producing fungi

A series of experiments was conducted to determine whether type I resistance (resistance to initial infection) to fusarium head blight (FHB) in wheat could be assessed using fungal species/isolates that do not produce deoxynivalenol (DON), a mycotoxin critical to the spread of Fusarium graminearum in the wheat spike. It was shown that, while the non-toxin-producing species Microdochium nivale and M. majus could infect following spray inoculation of wheat spikes, they were unable to spread within the spike following point inoculation. However, although these species might reveal type I resistance, they are not highly pathogenic towards wheat. A nivalenol (NIV)-producing isolate of F. graminearum caused high levels of disease following spray inoculation, but spread only very slowly within the spike and rarely induced bleaching above the point of inoculation. It is proposed that spray inoculation with an appropriate, aggressive, non-DON-producing FHB pathogen may be used to characterize type I resistance to complement point inoculation with a DON-producing isolate to assess type II resistance (resistance to spread within the spike).     

长江中下游地区亚洲镰刀菌NX-2毒素群体的检测

由禾谷镰刀菌复合种(Fusarium graminearum species complex,FGSC)引起的麦类赤霉病,是农业生产上的重要病害。为明确中国长江中下游冬小麦主产区小麦赤霉病菌种的构成及其地理分布,对2008年从江苏、浙江和湖北3省采集的656株小麦赤霉病菌株进行了分类鉴定。结果显示,其中558个菌株为亚洲镰刀菌(Fusarium asiaticum),98个菌株为禾谷镰刀菌(Fusarium graminearum sensu stricto),表明中国长江中下游冬小麦主产区小麦赤霉病的主要致病菌是亚洲镰刀菌。选择亚洲镰刀菌(F.asiaticum)为研究对象,通过PCR-RFLP的方法对其进行产NX-2毒素菌株的检测。结果没有检测到产NX-2毒素菌株,表明中国长江中下游冬小麦主产区并未出现NX-2毒素群体。本研究旨在了解NX-2毒素群体在中国长江中下游地区的地理分布,为进一步研究麦类赤霉病菌群体遗传多样性和演化趋势奠定基础,为麦类赤霉病的防治和毒素污染的控制提供理论依据。     

Diversity of Epidemic Populations of Gibberella zeae from Small Quadrats in Kansas and North Dakota

ABSTRACT Gibberella zeae (anamorph Fusarium graminearum) causes Fusarium head blight (FHB) of wheat and barley and has been responsible for several billion dollars of losses in the United States since the early 1990s. We isolated G. zeae from the top, middle, and bottom positions of wheat spikes collected from 0.25-m(2) quadrats during severe FHB epidemics in a single Kansas (KS) field (1993) and in a single North Dakota (ND) field (1994). Three amplified fragment length polymorphism (AFLP) primer pairs were used to resolve 94 polymorphic loci from 253 isolates. Members of a subset of 26 isolates also were tested for vegetative compatibility groups (VCGs). Both methods indicated high levels of genotypic variability and identified the same sets of isolates as probable clones. The mean number of AFLP multilocus haplotypes per head was approximately 1.8 in each population, but this value probably underestimates the true mean due to the small number of samples taken from each head. Isolates with the same AFLP haplotype often were recovered from different positions in a single head, but only rarely were such apparently clonal isolates recovered from more than one head within a quadrat, a pattern that is consistent with a genetically diverse initial inoculum and limited secondary spread. The KS and ND samples had no common AFLP haplotypes. All G. zeae isolates had high AFLP fingerprint similarity (>70%, unweighted pair group method with arithmetic means similarity) to reference isolates of G. zeae lineage 7. The genetic identity between the KS and ND populations was >99% and the estimated effective migration rate was high (Nm approximately 70). Tests for linkage disequilibrium provide little evidence for nonrandom associations between loci. Our results suggest that these populations are parts of a single, panmictic population that experiences frequent recombination. Our results also suggest that a variety of population sampling designs may be satisfactory for assessing diversity in this fungus.     

Fusarium populations on Chinese barley show a dramatic gradient in mycotoxin profiles

We report on a large gene bank of Fusarium isolates established by a broad survey conducted in 2005 in which infected barley ears were collected in 23 counties of seven provinces and two municipalities along the Yangtze River in China. In total, 1,894 single spore isolates were obtained. The isolates were characterized at the species level by a newly developed and robust set of diagnostic primers based on single nucleotide polymorphisms (SNPs) among members of the F. graminearum clade. In addition, we determined their chemotype using previously described polymerase chain reaction (PCR) primers. The results showed that in all regions F. asiaticum was the predominant species causing Fusarium head blight (FHB) on barley in China (N = 1,706), while in the upper valleys of the Yangtze River also F. graminearum sensu stricto, F. meridionale, and F. proliferatum were found. Major differences in the chemotypes were found in the F. asiaticum populations, from very high to exclusive nivalenol (NIV) chemotypes in the mountainous upper valleys of the Yangtze River to predominantly deoxynivalenol (DON) chemotypes in the middle and lower valleys. In contrast to the F. asiaticum isolates from three counties in Sichuan province, which were largely NIV producers (278 of 291), F. graminearum isolates from these sampling sites were for the vast majority (27 of 28) DON producers, indicating that despite sharing the same habitat, these sympatric species apparently have unique mycotoxin chemotypes.     

Comparison of commercial European wheat cultivars to Fusarium infection of head and seedling tissue

Susceptibility of eight commercial European wheat cultivars to fusarium head blight (FHB) disease caused by Fusarium graminearum , F. culmorum , F. poae and Microdochium nivale (formerly known as Fusarium nivale ) was compared under controlled environment conditions (16°C). FHB did not differentially affect cultivars in terms of disease symptoms, fungal DNA content of grain or deoxynivalenol (DON) contamination. However, the Hungarian-grown cultivars GK-Othalom and Fatima 2 (of Romanian origin) showed greater type V resistance (yield tolerance) to FHB than did the others. Also, nivalenol was produced by F. poae in these two cultivars and in Italian cultivar Norba, but not in other cultivars. Overall, significant relationships were found between the FHB and seedling blight resistance in vitro of these eight cultivars, but such relationships were generally highly dependent on cultivar, and therefore it is likely that the in vitro test is at best measuring components of FHB resistance and/or genotype-specific resistance components.     

Trichothecene mycotoxin genotypes of Fusarium graminearum sensu stricto and Fusarium meridionale in wheat from southern Brazil

A total of 82 fungal isolates was obtained from wheat kernel samples affected by fusarium head blight collected from 20 locations in southern Brazil. Polymerase chain reaction (PCR) assays were used to characterize trichothecene mycotoxin genotypes [deoxynivalenol (DON), nivalenol (NIV) and two acetylated derivatives of DON]. To identify isolates that producing DON and NIV, portions of the Tri13 gene were amplified. To identify 3-acetyl-deoxynivalenol (3-ADON) and 15-acetyl-deoxynivalenol (15-ADON) genotypes, portions of Tri3 and Tri12 were amplified. Nearly all of the isolates studied (76/82) were of the DON/15-ADON genotype. Six of the isolates were of the NIV genotype. The DON/3-ADON genotype was not observed. Portions of three genes were sequenced from representative isolates of the NIV and DON/15-ADON genotypes and compared with sequences from curated reference isolates of Fusarium in GenBank. blast queries for individual gene sequences and pairwise comparisons of percentage identity and percentage divergence based on 1676 bp of concatenated DNA sequence suggested that the isolates representing the DON/15-ADON genotype were Fusarium graminearum sensu stricto and the isolates representing the NIV genotype were Fusarium meridionale . This is the first detailed report of trichothecene mycotoxin genotypes of F. graminearum and F. meridionale in Brazil.     

不同杀菌剂对小麦赤霉病及籽粒DON毒素的控制效果

为探明不同杀菌剂对小麦赤霉病和小麦籽粒DON毒素(包括DON、3-ADON和15-ADON)的控制效果, 采用菌丝生长速率法测定了12种药剂对禾谷镰刀菌野生型菌株PH-1的室内活性, 同时采用液相色谱-串联质谱法(LC-MS)测定了这些药剂对DON毒素的抑制效果, 并开展了小麦赤霉病及籽粒DON毒素的田间防治试验。结果表明, 12种原药对菌丝生长抑制活性强弱依次为氟唑菌酰羟胺>咪鲜胺>戊唑醇>丙硫菌唑>叶菌唑>氰烯菌酯>氟环唑>多菌灵>甲基硫菌灵>吡唑醚菌酯>嘧菌酯>井冈霉素A。氟环唑EC50和EC90离体胁迫均刺激DON毒素产生, 其他杀菌剂EC50和EC90胁迫均抑制DON毒素产生。田间试验结果表明, 200 g/L氟唑菌酰羟胺SC、30%丙硫菌唑OD和20%叶菌唑WP病指防效和DON防效为87.68%~94.77%; 430 g/L戊唑醇SC、25%氰烯菌酯SC、45%咪鲜胺EW、25%氟环唑SC、50%多菌灵WP和70%甲基硫菌灵WP病指防效和DON防效为57.63%%~85.49%; 250 g/L吡唑醚菌酯EC和250 g/L嘧菌酯SC病指防效分别为72.18%和51.98%, DON防效分别为43.06%和-7.96%; 24%井冈霉素A AS病指防效和DON防效分别为42.37%和62.87%。药剂离体和田间控毒效果不完全一致, 赤霉病有效防控是DON防控的前提, 病害防效与DON防效不完全一致, 本研究为小麦赤霉病及籽粒DON毒素防控提供了科学依据。     

北京市及河北省小麦赤霉病菌群体遗传结构及生物学特性

本文分析了北京市与河北省小麦赤霉病菌群体遗传结构以及基础生物学特性。结果表明所有菌株均为禾谷镰刀菌(Fusarium graminearum),属于一个大的单一群体,群体内具有较高的遗传多样性。毒素化学型测定表明,北京与河北地区小麦真菌毒素污染的主要风险为DON与15ADON毒素。表型测定显示,与F.asiaticum群体相比,F.graminearum具有较高的产孢能力,而生长速率和产毒能力较低。该群体对主要杀菌剂多菌灵、戊唑醇和氰烯菌酯均无抗药性。     

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.     

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.     

Mapping of quantitative trait Loci for fusarium head blight resistance in barley

ABSTRACT Fusarium head blight (FHB) is a devastating disease that causes significant reductions in yield and quality in wheat and barley. Barley grains infected with deoxynivalenol (DON), a vomitoxin produced by Fusarium graminearum, are rejected for malting and brewing. Among six-rowed barley cultivars tested thus far, only cv. Chevron exhibited resistance. This study was conducted to map genes and to identify DNA markers for marker-assisted breeding for FHB resistance in cv. Chevron with restriction fragment length polymorphism (RFLP) markers. A doubled haploid (DH) population was created from a cross between cv. Chevron and susceptible cv. Stander. Seven field experiments were conducted in four different locations in 2 years. A RFLP map containing 211 loci and covering over 1,000 centimorgans (cM) of the genome was used to map quantitative trait loci (QTL) associated with relatively low FHB severity and DON concentration. Morphological traits differing between the parents were also measured: heading date, plant height, spike angle, number of nodes per cm of rachis in the spike, and kernel plumpness. Many of the QTL for FHB and DON coincided with QTLs for these morphological traits. The "fix-QTL" algorithm in Mapmaker QTL was used to remove the part of the variance for FHB resistance that may be explained by heading date or plant height. Results from this study suggest that QTLs with major effects for FHB resistance probably do not exist in cv. Chevron. Three QTL intervals, Xcmwg706-Xbcd441 on chromosome 1H, Xbcd307b-Xcdo684b on chromosome 2H, and Xcdo959b-Xabg472 on chromosome 4H, that are not associated with late heading or height may be useful for marker-assisted selection.     

Barley traits associated with resistance to fusarium head blight and deoxynivalenol accumulation

ABSTRACT Fusarium head blight (FHB) or scab is a destructive disease of barley in many countries. A better understanding of the interrelationships between plant traits and FHB resistance should help in the development of effective and efficient breeding strategies for FHB-resistant cultivars. Recent mapping studies indicate that many of the quantitative trait loci (QTL) for FHB resistance coincide with the QTL for plant height, heading date, and spike characteristics. Therefore, a study was conducted to investigate the relationship of morphological and physiological traits to FHB infection and deoxynivalenol (DON) accumulation in a barley doubled-haploid (DH) population derived from a Léger x CI9831 cross. Approximately 190 DH lines were grown at Ottawa (Ontario) for 2 years, Charlottetown (Prince Edward Island) for 1 year, and Hangzhou (Zhejiang) for 2 years. The field plots were inoculated with Fusarium graminearum at each location. FHB incidence was positively correlated with DON content. Resistance to FHB was associated with two-row spike, purple lemma, long glume awn, tall stature, and resistance to lodging, but it was not associated with long rachilla hairs, rough lemma awn, or heading date. Two-row spike was associated with tall stature and resistance to lodging. These associations as well as its spike characteristics helped reduce FHB infection and DON accumulation in two-row lines compared with six-row lines. The association between long glume awn and FHB resistance could be due to genetic linkages. Therefore, trait associations should be taken into consideration when breeding for FHB resistance and interpreting data from FHB experiments.     

Diversity in genetic structure and chemotype composition of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> sensu stricto populations causing wheat head blight in individual fields in Germany

Fusarium head blight (FHB) is one of the most destructive diseases of wheat. Twelve small commercial wheat fields (size 1–3 hectares) were sampled in Germany for Fusarium populations at three spots per field with 10 heads each. PCR assays using generic primers confirmed 338 isolates as F.graminearum sensu stricto (s.s.) (64.9%) out of 521 Fusarium spp. that were further analyzed. Populations of F. graminearum s.s. in Germany contain three types of trichothecenes with a dominancy of 15-acetyldeoxynivalenol chemotype (92%) followed by 3-acetyldeoxynivalenol chemotype (6.8%) and a few isolates of nivalenol chemotype (1.2%). All these isolates were genotyped using 19 microsatellite loci. The 12 populations showed a high genetic diversity within the small scale sampling areas resulting in 300 different haplotypes. Genetic diversity within populations (71.2%) was considerably higher than among populations (28.8%) as shown by analysis of molecular variance. Gene flow (Nm) between populations ranged from 0.76–3.16. Composition of haplotypes of one population followed over 2 years changed considerably. No correlation between genetic and geographical distance was found. In conclusion, populations of F. graminearum s.s. in Germany display a tremendous genetic variation on a local scale with a restricted diversity among populations.     

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.     

Trichothecene genotypes of Gibberella zeae from winter wheat fields in the eastern USA

Fusarium head blight (FHB), caused principally by Gibberella zeae (Fusarium graminearum), is a devastating disease of small grains such as wheat and barley worldwide. Grain infected with G. zeae may be contaminated with trichothecene mycotoxins such as deoxynivalenol (DON) and nivalenol (NIV). Strains of G. zeae that produce DON may also produce acetylated derivatives of DON: 3‐acetyl‐DON (3‐ADON) and 15‐acetyl‐DON (15‐ADON). Gradients (clines) of 3‐ADON genotypes in Canada have raised questions about the distribution of G. zeae trichothecene genotypes in wheat fields in the eastern USA. Tri3 and Tri12 genotypes were evaluated in 998 isolates of G. zeae collected from 39 winter wheat fields in New York (NY), Pennsylvania (PA), Maryland (MD), Virginia (VA), Kentucky (KY) and North Carolina (NC). Ninety‐two percent (919/998) of the isolates were 15‐ADON, 7% (69/998) were 3‐ADON, and 1% (10/998) was NIV. A phylogenetic analysis based on portions of three genes (PHO, RED and URA) from 23 isolates revealed two species of Fusarium (F. graminearum sensu stricto and one isolate of F. cerealis (synonym F. crookwellense)). An increasing trend of 3‐ADON genotypes was observed from NC (south) to NY (north). Punctuated episodes of atmospheric transport may favour a higher frequency of 3‐ADON genotypes in the northeastern USA, near Canada, compared with the mid‐Atlantic states. Discoveries of the NIV genotype in NY and NC indicate the need for more intensive sampling in the surrounding regions.     

不同小麦品种(系)对赤霉病的抗性和麦穗组织中DON毒素积累分析

 为明确不同小麦品种(系)对赤霉病的抗性和麦穗组织中DON毒素积累水平,培育和利用抗赤霉病和DON毒素积累的品种提供资源和依据,本研究采用单小花滴注接种法对河南省的106个小麦品种(系)抗赤霉病性进行鉴定分析,并用ELISA测定了病穗组织中DON毒素水平。结果表明不同小麦品种(系)对赤霉病的抗性有显著差异,106个小麦品种(系)中未发现抗病和中抗材料,中感品种(系)有华育198、郑麦103和春丰0021等14个,占13.2%;感病的有曌式2010-06、百农898和中麦63等92个,占86.8%。不同小麦品种(系)籽粒、颖壳和穗轴中DON毒素积累水平有显著差异,籽粒中DON毒素水平在(0.70~287.63)mg/kg之间,其中郑03876、豫保1号和中麦63 的DON毒素水平在2 mg/kg 以下,为抗毒素材料;其他的103个品种DON毒素水平大于2 mg/kg;颖壳和穗轴中的DON毒素水平在(51.03~392.87)mg/kg之间,普遍比籽粒中DON毒素含量高。籽粒中DON毒素水平与小麦品种(系)的平均病害严重度间呈极显著正相关。     

禾谷镰刀菌对苯基吡咯类杀菌剂咯菌腈的抗性机制

由禾谷镰刀菌引起的小麦赤霉病是世界小麦生产上的重要真菌病害。为了进一步明确禾谷镰刀菌对苯基吡咯类杀菌剂咯菌腈产生抗性的机制,本文以前期室内通过药剂驯化方式得到的4株禾谷镰刀菌对咯菌腈的高水平抗性突变体(其抗性倍数在318.2～782.9之间)为主要研究材料,采用生物测定及分子生物学等方法开展了禾谷镰刀菌对咯菌腈的抗性机制研究。结果表明：供试禾谷镰刀菌抗咯菌腈突变体对小麦幼穗的致病力降低了约50%,部分菌株(2XZ-4R)甚至完全丧失了对小麦的致病能力;抗性突变体对渗透胁迫(0.5 mol/L NaCl,1.0 mol/L MgCl₂, 1.0 mol/L葡萄糖或1.0 mol/L甘露醇)高度敏感,且菌丝生长抑制率较敏感菌株降低约50%以上,表明其环境适合度显著下降。同时,抗性突变体中苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和多酚氧化酶(PPO)活性较敏感菌株均升高2倍以上。分子生物学分析发现,供试抗性突变体中候选靶标基因(FgOs1和FgOs5)的表达量显著下调(P<0.05),推测FgOs1和FgOs5可能参与了禾谷镰刀菌对咯菌腈抗性的形成过程。总之...