First Report of Fusarium pseudograminearum Causing Crown Rot of Wheat in Henan, China

The critical roles of the Zn2Cys6 transcription factor Fp487 in the development and virulence of Fusarium pseudograminearum: A potential target for Fusarium crown rot control

Fusarium crown rot (FCR) caused by Fusarium pseudograminearum poses a significant threat to wheat production in the Huang-Huai-Hai region of China. However, the pathogenic mechanism of F. pseudograminearum is still poorly understood. Zn2Cys6 transcription factors, which are exclusive to fungi, play pivotal roles in regulating fungal development, drug resistance, pathogenicity, and secondary metabolism. In this study, we present the functional characterization of a Zn2Cys6 transcription factor F. pseudograminearum, designated Fp487. In F. pseudograminearum, Fp487 is shown to be required for mycelial growth through gene knockout and phenotypic analyses. Compared with wild-type CF14047, the ∆Fp487 mutant displayed a slight reduction in growth rate but a significant decrease in conidiogenesis, pathogenicity and 3-acetyl-deoxynivalenol (3AcDON) production. Moreover, the mutant exhibited heightened sensitivity to oxidative and cytomembrane stress. Furthermore, we synthesized dsRNA from the Fp487 gene in vitro, resulting in a reduction in the growth rate of F. pseudograminearum and its virulence on barley leaves through spray-induced gene silencing (SIGS). Notably, this study makes the first instance of inducing the expression of abundant dsRNA from F. pseudograminearum by engineering the Escherichia coli strain HT115 (DE3) and utilizing the SIGS technique to evaluate the virulence effect of dsRNA on F. pseudograminearum. In conclusion, our findings revealed the crucial role of Fp487 in regulating pathogenicity, stress responses, DON production, and conidiogenesis in F. pseudograminearum. Furthermore, Fp487 is a potential RNAi-based target for FCR control.

Development and application of multiplex PCR for the rapid identification of four Fusarium spp. associated with Fusarium crown rot in wheat

Fusarium crown rot (FCR), caused by Fusarium spp., is a devastating disease in wheat growing areas. Previous studies have shown that FCR is caused by co-infection of F. graminearum, F. pseudograminearum, F. proliferatum and F. verticillioides in Hubei Province, China. In this study, a method was developed to simultaneously detected DNAs of F. graminearum, F. pseudograminearum, F. proliferatum and F. verticillioides that can efficiently differentiate them. Whole genome sequence comparison of these four Fusarium spp. was performed and a 20 bp sequence was designed as an universal upstream primer. Specific downstream primers of each pathogen was also designed, which resulted in a 206, 482, 680, and 963 bp amplicon for each pathogen, respectively. Multiplex PCR specifically identified F. graminearum, F. pseudograminearum, F. proliferatum and F. verticillioides but not from other 46 pathogens, and the detection limit of target pathogens is about 100 pg/μl. Moreover, we accurately determined the FCR pathogen species in wheat samples using the optimized multiplex PCR method. These results demonstrate that the multiplex PCR method established in this study can efficiently and rapidly identify F. graminearum, F. pseudograminearum, F. proliferatum, and F. verticillioides, which should provide technical support for timely and targeted prevention and control of FCR.

Alternative splicing of the conserved drug-resistant orthologue FpNcb2 is associated with its nuclear accumulation of products and full virulence of Fusarium pseudograminearum

BACKGROUND

Negative cofactor 2 NC2β (Ncb2 or Dr1) is the beta subunit of a conserved heterodimeric regulator of transcription negative cofactor 2 (NC2) complex that has been identified as key regulator of drug resistance in model fungi. However, its role in plant pathogens is still unclear.

RESULTS

We identified an NC2β orthologue, FpNcb2, in Fusarium pseudograminearum, which is not only a significant regulatory function in drug resistance, but also essential for growth, conidiation and penetration. Moreover, FpNcb2 undergoes alternative splicing which creates two mRNA isoforms. As a putative CCAAT binding protein, FpNcb2 concentrates in the nuclei, contributing to the expression of two spliced mRNA of FpNcb2 in hypha, conidiophores and conidia, with exception of FpNcb2ISOA in germlings. Expression of each spliced mRNA of FpNcb2 in Δfpncb2 mutant could full complement the defects on growth, conidiation and fungicides sensitivity to that of wild type. However, FpNcb2ISOA and FpNcb2ISOB have different effects on virulence. FpNcb2 acts as a regulator for the transcription of some genes encoding drug efflux and hydrolases.

CONCLUSION

Our analysis showed the existence of alternative mRNA splicing in the NC2β orthologue, which is associated with protein subcellular localization and fungal virulence. The further elucidation of the target genes of NC2β will provide insights into the potential regulation mechanisms in the antifungal resistance and pathogenesis of F. pseudograminearum. © 2024 Society of Chemical Industry.

The G143S mutation in cytochrome b confers high resistance to pyraclostrobin in Fusarium pseudograminearum

BACKGROUND

Wheat crown rot (WCR), primarily caused by Fusarium pseudograminearum has become more and more prevalent in winter wheat areas in China. However, limited fungicides have been registered for the control of WCR in China so far. Pyraclostrobin is a representative quinone outside inhibitor (QoI) with excellent activity against Fusarium spp. There is currently limited research on the resistance risk and resistance mechanism of F. pseudograminearum to pyraclostrobin.

RESULTS

Here, we determined the activity of pyraclostrobin against F. pseudograminearum. The EC50 values ranged from 0.022 to 0.172 μg mL-1 with an average EC50 value of 0.071 ± 0.030 μg mL-1. Four highly pyraclostrobin-resistant mutants were obtained from two sensitive strains by ultraviolet (UV) mutagenesis in the laboratory. The mutants showed decreased mycelial growth rate and virulence as compared with the corresponding wild-type strains, indicating that pyraclostrobin resistance suffered a fitness penalty in F. pseudograminearum. It was found that the high resistance of four mutants was caused by the G143S mutation in Cytb. Molecular docking analysis also further confirms that the G143S mutation in Cytb decreased the binding affinity between pyraclostrobin and Cytb.

CONCLUSION

The resistance risk of F. pseudograminearum to pyraclostrobin could be low to medium. Although a mutation at the G143S position of Cytb could potentially occur, this mutation decreases the fitness of the mutant, which may reduce its survival in the environment. Therefore, the negative consequences of a possible mutation are lower. This makes pyraclostrobin a good candidate for controlling crown rot in wheat. © 2024 Society of Chemical Industry.

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.

Velvet Family Protein FpVelB Affects Virulence in Association with Secondary Metabolism in Fusarium pseudograminearum

Fusarium pseudograminearum causes destructive crown disease in wheat. The velvet protein family is a crucial regulator in development, virulence, and secondary metabolism of fungi. We conducted a functional analysis of FpVelB using a gene replacement strategy. The deletion of FpVelB decreased radial growth and enhanced conidial production compared to that of wild type. Furthermore, FpVelB modulates the fungal responses to abiotic stress through diverse mechanisms. Significantly, virulence decreased after the deletion of FpVelB in both the stem base and head of wheat. Genome-wide gene expression profiling revealed that the regulation of genes by FpVelB is associated with several processes related to the aforementioned phenotype, including "immune", "membrane", and "antioxidant activity", particularly with regard to secondary metabolites. Most importantly, we demonstrated that FpVelB regulates pathogen virulence by influencing deoxynivalenol production and modulating the expression of the PKS11 gene. In conclusion, FpVelB is crucial for plant growth, asexual development, and abiotic stress response and is essential for full virulence via secondary metabolism in F. pseudograminearum.

Histone H3 N-Terminal Lysine Acetylation Governs Fungal Growth, Conidiation, and Pathogenicity through Regulating Gene Expression in Fusarium pseudograminearum

The acetylation of histone lysine residues regulates multiple life processes, including growth, conidiation, and pathogenicity in filamentous pathogenic fungi. However, the specific function of each lysine residue at the N-terminus of histone H3 in phytopathogenic fungi remains unclear. In this study, we mutated the N-terminal lysine residues of histone H3 in Fusarium pseudograminearum, the main causal agent of Fusarium crown rot of wheat in China, which also produces deoxynivalenol (DON) toxins harmful to humans and animals. Our findings reveal that all the FpH3K9R, FpH3K14R, FpH3K18R, and FpH3K23R mutants are vital for vegetative growth and conidiation. Additionally, FpH3K14 regulates the pathogen's sensitivity to various stresses and fungicides. Despite the slowed growth of the FpH3K9R and FpH3K23R mutants, their pathogenicity towards wheat stems and heads remains unchanged. However, the FpH3K9R mutant produces more DON. Furthermore, the FpH3K14R and FpH3K18R mutants exhibit significantly reduced virulence, with the FpH3K18R mutant producing minimal DON. In the FpH3K9R, FpH3K14R, FpH3K18R, and FpH3K23R mutants, there are 1863, 1400, 1688, and 1806 downregulated genes, respectively, compared to the wild type. These downregulated genes include many that are crucial for growth, conidiation, pathogenicity, and DON production, as well as some essential genes. Gene ontology (GO) enrichment analysis indicates that genes downregulated in the FpH3K14R and FpH3K18R mutants are enriched for ribosome biogenesis, rRNA processing, and rRNA metabolic process. This suggests that the translation machinery is abnormal in the FpH3K14R and FpH3K18R mutants. Overall, our findings suggest that H3 N-terminal lysine residues are involved in regulating the expression of genes with important functions and are critical for fungal development and pathogenicity.

Fusarium pseudograminearum biomass and toxin accumulation in wheat tissues with and without Fusarium crown rot symptoms

Fusarium crown rot (FCR) is an important and devastating disease of wheat (Triticum aestivum) caused by the fungus Fusarium pseudograminearum and related pathogens. Using two distinct susceptible cultivars, we investigated the isolation frequencies of F. pseudograminearum and quantified its biomass accumulation and the levels of the associated toxins deoxynivalenol (DON) and DON-3-glucoside (D3G) in inoculated field-grown wheat plants. We detected F. pseudograminearum in stem, peduncle, rachis, and husk tissues, but not in grains, whereas DON and D3G accumulated in stem, rachis, husk, and grain tissues. Disease severity was positively correlated with the frequency of pathogen isolation, F. pseudograminearum biomass, and mycotoxin levels. The amount of F. pseudograminearum biomass and mycotoxin contents in asymptomatic tissue of diseased plants were associated with the distance of the tissue from the diseased internode and the disease severity of the plant. Thus, apparently healthy tissue may harbor F. pseudograminearum and contain associated mycotoxins. This research helps clarify the relationship between F. pseudograminearum occurrence, F. pseudograminearum biomass, and mycotoxin accumulation in tissues of susceptible wheat cultivars with or without disease symptoms, providing information that can lead to more effective control measures.

Genomics Analysis Reveals the Potential Biocontrol Mechanism of Pseudomonas aeruginosa QY43 against Fusarium pseudograminearum

Fusarium crown rot (FCR) in wheat is a prevalent soil-borne disease worldwide and poses a significant threat to the production of wheat (Triticum aestivum) in China, with F. pseudograminearum being the dominant pathogen. Currently, there is a shortage of biocontrol resources to control FCR induced by F. pseudograminearum, along with biocontrol mechanisms. In this study, we have identified 37 strains of biocontrol bacteria displaying antagonistic effects against F. pseudograminearum from over 8000 single colonies isolated from soil samples with a high incidence of FCR. Among them, QY43 exhibited remarkable efficacy in controlling FCR. Further analysis identified the isolate QY43 as Pseudomonas aeruginosa, based on its colony morphology and molecular biology. In vitro, QY43 significantly inhibited the growth, conidial germination, and the pathogenicity of F. pseudograminearum. In addition, QY43 exhibited a broad spectrum of antagonistic activities against several plant pathogens. The genomics analysis revealed that there are genes encoding potential biocontrol factors in the genome of QY43. The experimental results confirmed that QY43 secretes biocontrol factor siderophores and pyocyanin. In summary, QY43 exhibits a broad spectrum of antagonistic activities and the capacity to produce diverse biocontrol factors, thereby showing substantial potential for biocontrol applications to plant disease.

Development of a PCR-based assay for specific and sensitive detection of Fusarium buharicum from infected okra plant

Fusarium wilt, caused by the fungus Fusarium buharicum, is an emerging disease of okra in Japan. The disease was first reported in Japan in 2015, causing significant damage to okra seedlings. Due to the potential threat in okra cultivation, the development of an accurate detection method for F. buharicum is needed for the surveillance and management of the disease. In this study, we designed a primer set and developed conventional and nested PCR assays for the specific detection of F. buharicum in infected okra plants and contaminated soil, respectively. We compared the diversity of the translation elongation factor 1 alpha (EF-1α) gene of F. buharicum with 103 other fungal species/isolates to design a species-specific primer. This primer pair successfully amplified approximately 400 bp of PCR product that was only detected in the F. buharicum isolate, not in the other fungal isolates. The developed nested PCR method was highly sensitive and could detect the fungus from a 0.01 fg DNA sample. The primer successfully detected the pathogen in artificially infected plants and soil by conventional and nested PCR, respectively. This is the first report of the development of the F. buharicum-specific primer set and detection assays, which can be used for the specific and sensitive detection of F. buharicum in field samples and for taking early control measures.

Inhibitory activity to Fusarium spp. and control potential for wheat Fusarium crown rot of a novel succinate dehydrogenase inhibitor cyclobutrifluram

BACKGROUND

Wheat Fusarium crown rot (FCR) is a serious problem primarily caused by Fusarium pseudograminearum, a pathogenic agent known to produce mycotoxins, including deoxynivalenol (DON). Cyclobutrifluram, a novel succinate dehydrogenase inhibitor devised by Syngenta, has immense potential to control both nematodes and Fusarium diseases. However, its efficacy in combating Fusarium species, its ability to prevent and reverse the detrimental effects of FCR, and its impact on the production of DON by F. pseudograminearum are yet to be fully ascertained.

RESULTS

Cyclobutrifluram exhibited substantial inhibitory activity against Fusarium species, with half-maximal effective concentration values ranging from 0.0021-0.0647 μg mL-1 . It demonstrated significant inhibitory activity toward three developmental stages of F. pseudograminearum, F. graminearum and F. asiaticum. Furthermore, cyclobutrifluram showed both protective and curative activities against FCR and was rapidly absorbed by roots and transported to wheat stems and leaves. Cyclobutrifluram could also decrease DON production by F. pseudograminearum.

CONCLUSION

This investigation has revealed the potential of cyclobutrifluram as a formidable candidate fungicide, particularly in its ability to effectively combat FCR and other Fusarium-related ailments. This novel compound has exceptional pathogen-fighting capabilities, coupled with remarkable systemic translocation properties and a notable ability to reduce the production of DON. © 2023 Society of Chemical Industry.

Population Genetic Analyses and Trichothecene Genotype Profiling of Fusarium pseudograminearum Causing Wheat Crown Rot in Henan, China

In China, Fusarium pseudograminearum has emerged as a major pathogen causing Fusarium crown rot (FCR) and caused significant losses. Studies on the pathogen's properties, especially its mating type and trichothecene chemotypes, are critical with respect to disease epidemiology and food/feed safety. There are currently few available reports on these issues. This study investigated the species composition, mating type idiomorphs, and trichothecene genotypes of Fusarium spp. causing FCR in Henan, China. A significant shift in F. pseudograminearum-induced FCR was found in the present study. Of the 144 purified strains, 143 were F. pseudograminearum, whereas only 1 Fusarium graminearum was identified. Moreover, a significant trichothecene-producing capability of F. pseudograminearum strains from Henan was observed in this work. Among the 143 F. pseudograminearum strains identified, F. pseudograminearum with a 15ADON genotype was found to be predominant (133 isolates), accounting for 92.36% of all strains, followed by F. pseudograminearum with a 3ADON genotype, whereas only one NIV genotype strain was detected. Overall, a relatively well-balanced 1:1 ratio of the F. pseudograminearum population was found in Henan. To the best of our knowledge, this is the first study that has examined the Fusarium populations responsible for FCR across the Henan wheat-growing region.

A critical review on bioaerosols-dispersal of crop pathogenic microorganisms and their impact on crop yield

Bioaerosols are potential sources of pathogenic microorganisms that can cause devastating outbreaks of global crop diseases. Various microorganisms, insects and viroids are known to cause severe crop diseases impeding global agro-economy. Such losses threaten global food security, as it is estimated that almost 821 million people are underfed due to global crisis in food production. It is estimated that global population would reach 10 billion by 2050. Hence, it is imperative to substantially increase global food production to about 60% more than the existing levels. To meet the increasing demand, it is essential to control crop diseases and increase yield. Better understanding of the dispersive nature of bioaerosols, seasonal variations, regional diversity and load would enable in formulating improved strategies to control disease severity, onset and spread. Further, insights on regional and global bioaerosol composition and dissemination would help in predicting and preventing endemic and epidemic outbreaks of crop diseases. Advanced knowledge of the factors influencing disease onset and progress, mechanism of pathogen attachment and penetration, dispersal of pathogens, life cycle and the mode of infection, aid the development and implementation of species-specific and region-specific preventive strategies to control crop diseases. Intriguingly, development of R gene-mediated resistant varieties has shown promising results in controlling crop diseases. Forthcoming studies on the development of an appropriately stacked R gene with a wide range of resistance to crop diseases would enable proper management and yield. The article reviews various aspects of pathogenic bioaerosols, pathogen invasion and infestation, crop diseases and yield.

A novel QTL conferring Fusarium crown rot resistance on chromosome 2A in a wheat EMS mutant

KEY MESSAGE

A novel QTL on chromosome 2A for Fusarium crown rot resistance was identified and validated in wheat. Fusarium crown rot (FCR) is a fungal disease that causes significant yield losses in many cereal growing regions in the world. In this study, genetic analysis was conducted for a wheat EMS mutant C549 which showed stable resistance to FCR at seedling stage. A total of 10 QTL were detected on chromosomes 1A, 2A, 3B, 4A, 6B, and 7B using a population of 138 F7 recombinant inbred lines (RILs) derived from a cross between C549 and a Chinese germplasm 3642. A novel locus Qfcr.cau-2A, which accounted for up to 24.42% of the phenotypic variation with a LOD value of 12.78, was consistently detected across all six trials conducted. Furthermore, possible effects of heading date (HD) and plant height on FCR severity were also investigated in the mapping population. While plant height had no effects on FCR resistance, a weak and negative association between FCR resistance and HD was observed. A QTL for HD (Qhd.cau-2A.2) was coincident with Qfcr.cau-2A. Conditional QTL mapping indicated that although Qfcr.cau-2A and Qhd.cau-2A.2 had significant interactions, Qfcr.cau-2A remained significant after the effects of HD was removed. It is unlikely that genes underlying these two loci are same. Nevertheless, the stable expression of Qfcr.cau-2A in the validation population of 148 F7 RILs developed between C549 and its wild parent Chuannong 16 demonstrated the potential value of this locus in FCR resistance breeding programs.

Screening and Resistance Locus Identification of the Mutant fcrZ22 Resistant to Crown Rot Caused by Fusarium pseudograminearum

Crown rot caused by Fusarium pseudograminearum is a devastating wheat disease worldwide. In addition to yield losses, the fungi causing Fusarium crown rot (FCR) also deteriorate the quality and safety of food because of the production of mycotoxins. Planting resistant cultivars is an effective way to control FCR. However, most wheat cultivars are susceptible to FCR. Therefore, development of new sources and detection of loci for FCR resistance are necessary. In the present study, a resistant mutant, fcrZ22, was identified from an ethyl methane sulfonate (EMS)-mutagenized population of the cultivar Zhoumai 22, and then fcrZ22 was crossed with the wild type to produce an F2 population. Genetic analysis of the F2 population was carried out by the mixed inheritance model of major genes plus polygenes, and 20 resistant and 20 susceptible plants were selected to assemble mixed pools. Combining 660K SNP arrays, the resistance loci were detected by bulked segregant analysis. The resistance to FCR caused by F. pseudograminearum in the F2 population was in accordance with the "mixed model with two major genes of additive-epistasis effect + additive-dominant polygenes," and the heritability of the major gene was 0.92. Twenty-one loci were detected, which were located on 10 chromosomes, namely, 1B (1), 1D (1), 2A (3), 1B (1), 3A (3), 3B (3), 4A (2), 5A (2), 7A (3), and 7B (2). Among the 21 loci, eight were new loci for FCR resistance. This is the first report of detecting loci for FCR resistance from a mutant. The results of the present study provided excellent germplasm resources for breeding wheat cultivars with FCR resistance and laid the foundation for fine mapping of FCR resistance loci.

Mefentrifluconazole-Resistant Risk and Resistance-Related Point Mutation in FpCYP51B of Fusarium pseudograminearum

Mefentrifluconazole, a triazole fungicide, exhibits remarkable efficacy in combating Fusarium spp. The mean EC50 value of mefentrifluconazole against 124 isolates of Fusarium pseudograminearum was determined to be 1.06 μg/mL in this study. Fungicide taming produced five mefentrifluconazole-resistant mutants with resistance factors ranging from 19.21 to 111.34. Compared to the original parental isolates, the fitness of three resistant mutants was much lower, while the remaining two mutants displayed enhanced survival fitness. There was evidence of positive cross-resistance between tebuconazole and mefentrifluconazole. Mefentrifluconazole resistance in F. pseudograminearum can be conferred by FpCYP51BL144F, which was identified in four mutants according to molecular docking and site-directed transformation experiments. Overexpression of FpCYP51s was also detected in the resistant mutants. In conclusion, mefentrifluconazole has a low-to-medium resistance risk in F. pseudograminearum, and the L144F mutation in FpCYP51B and the increased expression level of FpCYP51s may be responsible for mefentrifluconazole resistance in F. pseudograminearum.

Antagonistic effects of Talaromyces muroii TM28 against Fusarium crown rot of wheat caused by Fusarium pseudograminearum

Fusarium crown rot (FCR) caused by Fusarium pseudograminearum is a serious threat to wheat production worldwide. This study aimed to assess the effects of Talaromyces muroii strain TM28 isolated from root of Panax quinquefolius against F. pseudograminearum. The strain of TM28 inhibited mycelial growth of F. pseudograminearum by 87.8% at 72 h, its cell free fermentation filtrate had a strong antagonistic effect on mycelial growth and conidial germination of F. pseudograminearum by destroying the integrity of the cell membrane. In the greenhouse, TM28 significantly increased wheat fresh weight and height in the presence of pathogen Fp, it enhanced the antioxidant defense activity and ameliorated the negative effects of F. pseudograminearum, including disease severity and pathogen abundance in the rhizosphere soil, root and stem base of wheat. RNA-seq of F. pseudograminearum under TM28 antagonistic revealed 2,823 differentially expressed genes (DEGs). Most DEGs related to cell wall and cell membrane synthesis were significantly downregulated, the culture filtrate of TM28 affected the pathways of fatty acid synthesis, steroid synthesis, glycolysis, and the citrate acid cycle. T. muroii TM28 appears to have significant potential in controlling wheat Fusarium crown rot caused by F. pseudograminearum.

Efficacy of cyclobutrifluram in controlling Fusarium crown rot of wheat and resistance risk of three Fusarium species to cyclobutrifluram

Cyclobutrifluram (TYMIRIUM® technology), a new succinate dehydrogenase inhibitor (SDHI) fungicide, is currently being registered by SYNGENTA for controlling Fusarium crown rot (FCR) of wheat in China. The application of 15 or 30 g of active ingredient/100 kg seed of cyclobutrifluram significantly reduced pre-emergence damping-off, discoloration on the stem base and formation of whiteheads caused by FCR. The EC50 values of cyclobutrifluram for 60 isolates of F. pseudograminearum, 30 isolates of F. asiaticum and 30 isolates of F. graminearum ranged from 0.016 to 0.142 mg L-1, 0.010 to 0.041 mg L-1 and 0.012 to 0.059 mg L-1, respectively. One hundred and seven cyclobutrifluram-resistant (CR) mutants were obtained from three Fusarium species isolates, with ten types of mutations identified in Sdh genes. Three Fusarium species isolates exhibited similar resistance mechanisms, with the most prevalent mutations, SdhC1A83V and SdhC1R86K, accounting for 61.68% of mutants. The CR mutants possessed comparable or slightly impaired fitness compared to the corresponding parental isolates. The CR mutants carrying FpSdhBH248Y/Q/D exhibited increased sensitivity to fluopyram. An overall moderate risk of resistance development in three Fusarium species was recommended for cyclobutrifluram.

Impact of Phenamacril on the Growth and Development of Fusarium pseudograminearum and Control of Crown Rot of Wheat

Fusarium pseudograminearum is the dominant pathogen causing Fusarium crown rot (FCR) of wheat. Phenamacril is a 2-cyanoacrylate fungicide, having a control effect on diseases caused by Fusarium spp. The objective of this study was to investigate the inhibitory effect of phenamacril on F. pseudograminearum and its control efficacy against FCR. The results showed that phenamacril had a strong inhibitory effect on the mycelial growth of F. pseudograminearum, EC50 values of phenamacril to 63 tested strains were in the range of 0.0998 to 0.5672 μg/ml, and the average EC50 value was 0.3403 ± 0.0872 μg/ml and could be used as the baseline sensitivity of F. pseudograminearum to phenamacril. Phenamacril reduced the germination rate of conidia of F. pseudograminearum, and the EC50 value was 5.0273 to 26.4814 μg/ml. In addition, we found that phenamacril had a teratogenic effect on conidia and blastotubules, which increased the ratio of conidial germination from the middle cells and showed high efficacy on the sporulation quantity of F. pseudograminearum with an EC50 value in the range of 0.0770 to 0.1064 μg/ml. There was no significant correlation between the sensitivity of F. pseudograminearum to phenamacril and its sensitivity to fludioxonil, carbendazim, tebuconazole, and kresoxim-methyl. In vitro and greenhouse assays showed that the treatment with 0.125 μl of active ingredient per gram recorded the best control effect on wheat crown rot, reaching 87.8 and 77.3%, respectively. In two experimental sites in Luoyang, phenamacril also had great control effect against FCR, reaching 83.9%. It was proven that phenamacril has a superior control effect against FCR. This study has laid a foundation for the study of the mechanism of action of phenamacril against F. pseudograminearum and provided a theoretical basis for the application of phenamacril to control FCR.

Resistant risk and resistance-related point mutation in SdhC1 of pydiflumetofen in Fusarium pseudograminearum

BACKGROUND

Fusarium pseudograminearum is one of the dominant pathogens of Fusarium crown rot (FCR) worldwide. Unfortunately, no fungicides have yet been registered for the control of FCR in wheat in China. Pydiflumetofen, a new-generation succinate dehydrogenase inhibitor, exhibits excellent inhibitory activity to Fusarium spp. A resistance risk assessment of F. pseudograminearum to pydiflumetofen and the resistance mechanism involved have not yet been investigated.

RESULTS

The median effective concentration (EC50 ) value of 103 F. pseudograminearum isolates to pydiflumetofen was 0.0162 μg mL-1 , and the sensitivity exhibited a unimodal distribution. Four resistant mutants were generated by fungicide adaption, which possessed similar or impaired fitness compared to corresponding parental isolates based on the results of mycelial growth, conidiation, conidium germination rate, and virulence determination. Pydiflumetofen showed strong positive cross-resistance with cyclobutrifluram and fluopyram but no cross-resistance with carbendazim, phenamacril, tebuconazole, fludioxonil, or pyraclostrobin. Sequence alignment revealed that pydiflumetofen-resistant F. pseudograminearum mutants had two single-point mutations of A83V or R86K in FpSdhC1 . Molecular docking further confirmed that point mutation of A83V or R86K in FpSdhC1 could confer resistance of F. pseudograminearum to pydiflumetofen.

CONCLUSION

Fusarium pseudograminearum shows an overall moderate risk of developing resistance to pydiflumetofen, and point mutation FpSdhC1 A83V or FpSdhC1 R86K could confer pydiflumetofen resistance in F. pseudograminearum. This study provided vital data for monitoring the emergence of resistance and developing resistance management strategies for pydiflumetofen. © 2023 Society of Chemical Industry.

Baseline Pydiflumetofen Sensitivity of Fusarium pseudograminearum Isolates Collected from Henan, China, and Potential Resistance Mechanisms

Fusarium crown rot (FCR), caused by Fusarium pseudograminearum, is one of the most important diseases impacting wheat production in the Huanghuai region, the most important wheat-growing region of China. The current study found that the SDHI fungicide pydiflumetofen, which was recently developed by Syngenta Crop Protection, provided effective control of 67 wild-type F. pseudograminearum isolates in potato dextrose agar, with an average EC50 value of 0.060 ± 0.0098 μg/ml (SE). Further investigation revealed that the risk of fungicide resistance in pydiflumetofen was medium to high. Four F. pseudograminearum mutants generated by repeated exposure to pydiflumetofen under laboratory conditions indicated that pydiflumetofen resistance was associated with fitness penalties. Mutants exhibited significantly (P < 0.05) reduced sporulation in mung bean broth and significantly (P < 0.05) reduced pathogenicity in wheat seedlings. Sequence analysis indicated that the observed pydiflumetofen resistance of the mutants was likely associated with amino acid changes in the different subunits of the succinate dehydrogenase target protein, including R18L and V160M substitutions in the FpSdhA sequence; D69V, D147G, and C257R in FpSdhB; and W78R in FpSdhC. This study found no evidence of cross-resistance between pydiflumetofen and the alternative fungicides tebuconazole, fludioxonil, carbendazim, or fluazinam, which all have distinct modes of action and could therefore be used in combination or rotation with pydiflumetofen to reduce the risk of resistance emerging in the field. Taken together, these results indicate that pydiflumetofen has potential as a novel fungicide for the control of FCR caused by F. pseudograminearum and could therefore be of great significance in ensuring high and stable wheat yields in China.

A Putative Zn(II)2Cys6-Type Transcription Factor FpUme18 Is Required for Development, Conidiation, Cell Wall Integrity, Endocytosis and Full Virulence in Fusarium pseudograminearum

Fusarium pseudograminearum is one of the major fungal pathogens that cause Fusarium crown rot (FCR) worldwide and can lead to a substantially reduced grain yield and quality. Transcription factors play an important role in regulating growth and pathogenicity in plant pathogens. In this study, we identified a putative Zn(II)2Cys6 fungal-type domain-containing transcription factor and named it FpUme18. The expression of FpUME18 was induced during the infection of wheat by F. pseudograminearum. The ΔFpume18 deletion mutant showed defects in growth, conidial production, and conidial germination. In the responses to the cell wall, salt and oxidative stresses, the ΔFpume18 mutant inhibited the rate of mycelial growth at a higher rate compared with the wild type. The staining of conidia and mycelia with lipophilic dye FM4-64 revealed a delay in endocytosis when FpUME18 was deleted. FpUME18 also positively regulated the expression of phospholipid-related synthesis genes. The deletion of FpUME18 attenuated the pathogenicity of wheat coleoptiles. FpUME18 also participated in the production of the DON toxin by regulating the expression of TRI genes. Collectively, FpUme18 is required for vegetative growth, conidiation, stress response, endocytosis, and full virulence in F. pseudograminearum.

Genome-wide association analysis of Fusarium crown rot resistance in Chinese wheat landraces

KEY MESSAGE

A novel locus for Fusarium crown rot (FCR) resistance was identified on chromosome 1B at 641.36-645.13 Mb using GWAS and could averagely increase 39.66% of FCR resistance in a biparental population. Fusarium crown rot can cause considerable yield losses. Developing and growing resistance cultivars is one of the most effective approaches for controlling this disease. In this study, 361 Chinese wheat landraces were evaluated for FCR resistance, and 27 with the disease index lower than 30.00 showed potential in wheat breeding programs. Using a genome-wide association study approach, putative quantitative trait loci (QTL) for FCR resistance was identified. A total of 21 putative loci on chromosomes 1A, 1B, 2B, 2D, 3B, 3D, 4B, 5A, 5B, 7A, and 7B were significantly associated with FCR resistance. Among these, a major locus Qfcr.sicau.1B-4 was consistently identified among all the trials on chromosome 1B with the physical regions from 641.36 to 645.13 Mb. A polymorphism kompetitive allele-specific polymerase (KASP) marker was developed and used to validate its effect in an F_2:3 population consisting of 136 lines. The results showed the presence of this resistance allele could explain up to 39.66% of phenotypic variance compared to its counterparts. In addition, quantitative real-time polymerase chain reaction showed that two candidate genes of Qfcr.sicau.1B-4 were differently expressed after inoculation. Our study provided useful information for improving FCR resistance in wheat.

Resistance risk assessment of Fusarium pseudograminearum from wheat to prothioconazole

Fusarium crown rot (FCR), primarily caused by Fusarium pseudograminearum, poses significant threats to cereal crops worldwide. Prothioconazole is a demethylation inhibitor (DMI) fungicide used to control FCR. However, the risk of resistance in F. pseudograminearum to prothioconazole has not yet been evaluated. In this study, the sensitivity of a total of 255 F. pseudograminearum strains obtained from Henan Province, China to prothioconazole were determined by the mycelial growth inhibition. The results showed that the effective concentration to 50% growth inhibition (EC₅₀) of these strains ranged from 0.4228 μg/mL to 2.5284 μg/mL, with a mean EC₅₀ value of 1.0692 ± 0.4527 μg/mL (mean ± SD). Thirty prothioconazole-resistant mutants were obtained out of six selected sensitive parental strains by means of fungicide taming. The resistant mutants exhibited defects in vegetative growth, conidia production, and pathogenicity on wheat seedlings compared to their parental strains. Under ion, cell wall, and temperature stress conditions but not osmotic stress, all the mutants exhibited decreased growth rates compared with their parental strains, which was consistent with the control treatment. Cross-resistance test showed that there was a cross-resistance relationship between prothioconazole and four DMI fungicides, including prochloraz, metconazole, tebuconazole and hexaconazole, but no cross-resistance was observed between prothioconazole and carbendazim, phenamacril, fludioxonil, or azoxystrobin. Although no site mutation occurred on Cyp51a and Cyp51b genes, the constitutive expression level of the Cyp51a gene was significantly increased in all mutants. After being treated with prothioconazole, the Cyp51a and Cyp51b genes were significantly increased in both the resistant mutants and their parents. These results suggested that the resistance to prothioconazole of the mutants may be attributed to the changes of the relative expression level of Cyp51a and Cyp51b genes. Taken together, these results could provide a theoretical basis for the scientific use of prothioconazole in the field and fungicide resistance management strategies.

Transcriptomic Profiling of Fusarium pseudograminearum in Response to Carbendazim, Pyraclostrobin, Tebuconazole, and Phenamacril

Fusarium pseudograminearum has been identified as a significant pathogen. It causes Fusarium crown rot (FCR), which occurs in several major wheat-producing areas in China. Chemical control is the primary measure with which to control this disease. In this study, transcriptome sequencing (RNA-Seq) was used to determine the different mechanisms of action of four frequently used fungicides including carbendazim, pyraclostrobin, tebuconazole, and phenamacril on F. pseudograminearum. In brief, 381, 1896, 842, and 814 differentially expressed genes (DEGs) were identified under the carbendazim, pyraclostrobin, tebuconazole, and phenamacril treatments, respectively. After the joint analysis, 67 common DEGs were obtained, and further functional analysis showed that the ABC transported pathway was significantly enriched. Moreover, FPSE_04130 (FER6) and FPSE_11895 (MDR1), two important ABC multidrug transporter genes whose expression levels simultaneously increased, were mined under the different treatments, which unambiguously demonstrated the common effects. In addition, Mfuzz clustering analysis and WGCNA analysis revealed that the core DEGs are involved in several critical pathways in each of the four treatment groups. Taken together, these genes may play a crucial function in the mechanisms of F. pseudograminearum's response to the fungicides stress.

A Novel Wall-Associated Kinase TaWAK-5D600 Positively Participates in Defense against Sharp Eyespot and Fusarium Crown Rot in Wheat

Sharp eyespot and Fusarium crown rot, mainly caused by soil-borne fungi Rhizoctonia cerealis and Fusarium pseudograminearum, are destructive diseases of major cereal crops including wheat (Triticum aestivum). However, the mechanisms underlying wheat-resistant responses to the two pathogens are largely elusive. In this study, we performed a genome-wide analysis of wall-associated kinase (WAK) family in wheat. As a result, a total of 140 TaWAK (not TaWAKL) candidate genes were identified from the wheat genome, each of which contains an N-terminal signal peptide, a galacturonan binding domain, an EGF-like domain, a calcium binding EGF domain (EGF-Ca), a transmembrane domain, and an intracellular Serine/Threonine protein kinase domain. By analyzing the RNA-sequencing data of wheat inoculated with R. cerealis and F. pseudograminearum, we found that transcript abundance of TaWAK-5D600 (TraesCS5D02G268600) on chromosome 5D was significantly upregulated, and that its upregulated transcript levels in response to both pathogens were higher compared with other TaWAK genes. Importantly, knock-down of TaWAK-5D600 transcript impaired wheat resistance against the fungal pathogens R. cerealis and F. pseudograminearum, and significantly repressed expression of defense-related genes in wheat, TaSERK1, TaMPK3, TaPR1, TaChitinase3, and TaChitinase4. Thus, this study proposes TaWAK-5D600 as a promising gene for improving wheat broad resistance to sharp eyespot and Fusarium crown rot (FCR) in wheat.

The global regulator FpLaeB is required for the regulation of growth, development, and virulence in Fusarium pseudograminearum

Fusarium pseudograminearum is a soil-borne pathogen that is capable of causing a highly destructive crown disease in wheat. Secondary metabolites (SMs), especially deoxynivalenol (DON), are the primary virulence factors during infection. Here, we characterised the global regulator FpLaeB, an orthologue of LaeB protein function, to regulate the SM in Aspergillus nidulans. Through the utility of the gene targeting approach, we found that the vegetative growth of the FpLaeB deletion mutant was drastically reduced compared to that of the wild type. FpLaeB was also important for conidiation because the FpLaeB deletion mutant formed fewer conidia in induced medium. In addition, the sensitivity of the FpLaeB deletion mutant to the cell wall integrity inhibitor was decreased, while its growth was more severely inhibited by the cell membrane inhibitor sodium dodecyl sulfate (SDS) than that of the wild type. More importantly, the virulence was decreased when the FpLaeB deletion mutant was inoculated onto the wheat stem base or head. Through genome-wide gene expression profiling, FpLaeB was found to regulate several processes related to the above phenotypes such as the carbohydrate metabolic process, which is an integral and intrinsic component of membranes, especially SMs. Furthermore, the generation of DON was impaired in the FpLaeB deletion mutant via ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay. These results showed that FpLaeB plays an important role in the growth, development, and maintenance of the cell wall, and in membrane integrity. More importantly, FpLaeB is required for SMs and full virulence in F. pseudograminearum.

Antifungal activities of metconazole against the emerging wheat pathogen Fusarium pseudograminearum

Fusarium crown rot of wheat is a serious fungal disease that occurs worldwide. The disease has been emerging in the major wheat-growing areas in China since 2010. Fusarium pseudogramineaum is the predominant causative pathogen of crown rot of wheat in China. The 14α-demethylation inhibitor (DMI) fungicide metconazole has been shown to be effective against Fusarium spp., but little is known about its specific activity against F. pseudogramineaum. Metconazole exhibited strong antifungal activities against all thirty-nine F. pseudogramineaum strains collected from the major wheat-growing areas in China. Metconazole inhibited mycelial growth and conidial germ tube elongation of F. pseudograminearum. Metconazole treatment significantly reduced the production of major toxins and the expression levels of toxin biosynthesis genes. Genome-wide transcriptional profiling of F. pseudograminearum in response to metconazole indicated that the expression of genes involved in ergosterol biosynthesis, including fungicide target genes (cyp51 genes), was significantly induced by metconazole. Nine ATP-binding cassette (ABC) transporter-encoding genes were significantly expressed in response to metconazole treatment. Reduced ergosterol production and antioxidant enzyme activities were observed after metconazole treatment. Greenhouse experiments indicated a significant reduction in crown rot occurrence in wheat after seed treatment with metconazole. This study evaluated the potential of metconazole to manage wheat crown rot and provides information to understand its antifungal activities and mechanism of action against F. pseudograminearum.

Resistance Risk and Resistance-Related Point Mutation in SdhB and SdhC1 of Cyclobutrifluram in Fusarium pseudograminearum

Cyclobutrifluram is a novel succinate dehydrogenase inhibitor (SDHI) developed by Syngenta and helps to inhibit Fusarium pseudograminearum. Here, the potential for cyclobutrifluram resistance in F. pseudograminearum and the resistance mechanism involved were evaluated. Baseline sensitivity of F. pseudograminearum to cyclobutrifluram was determined with a mean EC₅₀ value of 0.0248 μg/mL. Fungicide adaption generated five resistant mutants, which possess a comparable or a slightly impaired fitness compared to corresponding parental isolates. This indicates that the resistance risk of F. pseudograminearum to cyclobutrifluram might be moderate. Cyclobutrifluram-resistant isolates also demonstrated resistance to pydiflumetofen but sensitivity to carbendazim, phenamacril, tebuconazole, fludioxonil, or pyraclostrobin. Additionally, point mutations H248Y in FpSdhB and A83V or R86K in FpSdhC₁ were found in cyclobutrifluram-resistant F. pseudograminearum mutants. Molecular docking and overexpression transformation assay revealed that FpSdhB^H248Y and FpSdhC₁^A83V or FpSdhC₁^R86K confer the resistance of F. pseudograminearum to cyclobutrifluram.

Detection of fungicide resistance to fludioxonil and tebuconazole in Fusarium pseudograminearum, the causal agent of Fusarium crown rot in wheat

Fusarium crown rot (FCR) on wheat is a soil-borne disease that affects the yield and quality of the produce. In 2020, 297 Fusarium pseudograminearum isolates were isolated from diseased FCR wheat samples from eight regional areas across Hebei Province in China. Baseline sensitivity of F. pseudograminearum to fludioxonil (0.0613 ± 0.0347 μg/mL) and tebuconazole (0.2328 ± 0.0840 μg/mL) were constructed based on the in vitro tests of 71 and 83 isolates, respectively. The resistance index analysis showed no resistance isolate to fludioxonil but two low-resistance isolates to tebuconazole in 2020. There was an increased frequency of resistant isolates from 2021 to 2022 based on the baseline sensitivity for tebuconazole. There was no cross-resistance between fludioxonil and tebuconazole. This study provides a significant theoretical and practical basis for monitoring the resistance of F. pseudograminearum to fungicides, especially the control of FCR.

Genome sequence resource of Pectobacterium polaris QK413-1 that causes blackleg on potato in Fujian Province, China

The Pectobacterium pathogens cause soft rot and blackleg diseases on many plants and crops, including potatoes. Here we first report a high-quality genome assembly and announcement of the P. polaris strain QK413-1, which causes blackleg disease in potatoes in China. The QK413-1 genome was sequenced and assembled using the PacBio Sequel II and Illumina sequencing platform. The assembled genome has a total size of 5,005,507bp with a GC content of 51.81%, encoding 4782 open reading frames, including 639 virulence genes, 273 drug resistance genes, and 416 secreted proteins. The QK413-1 genome sequence provides a valuable resource for the control of potato blackleg and research into its mechanism.

Baseline Sensitivity and Potential Resistance Mechanisms for Fusarium pseudograminearum to Fludioxonil

Fusarium crown rot (FCR), which is caused by Fusarium pseudograminearum, is one of the most important diseases affecting wheat production in the Huanghuai wheat-growing region of China. Although the phenylpyrrole fungicide fludioxonil is known to have a broad-spectrum activity against a wide range of plant pathogens, including F. pseudograminearum, it has not yet been registered for the control of FCR in China, and further research is needed to assess the biological characteristics and molecular mechanisms associated with fludioxonil resistance, and especially the potential for highly resistant isolates to emerge. The current study demonstrated that the baseline fludioxonil sensitivity of 61 F. pseudograminearum isolates collected from the Henan province of China during the summers of 2019 to 2021 conformed to a unimodal distribution with a mean effective concentration for 50% inhibition (EC₅₀) value of 0.021 ± 0.003 μg/ml, which indicated that none of the isolates exhibited natural resistance to fludioxonil. Nevertheless, four fludioxonil-resistant mutants were attained after repeated exposure to fludioxonil under laboratory conditions. All resistant mutants exhibited significantly lower growth rates on potato dextrose agar (PDA) and lower levels of sporulation and pathogenicity in wheat seedlings. In addition, the resistant mutants also exhibited less growth on PDA amended with either 0.5 M mannitol, 0.5 M glucose, 0.5 M MgCl₂, or 0.5 M NaCl, which indicated that they had greater sensitivity to osmotic stress. Molecular analysis of the proposed fludioxonil target protein FpOs1 indicated that the predicted sequences of the resistant mutants contained none of the characteristic amino acid changes previously associated with fludioxonil resistance in other species. Further investigation via quantitative real-time PCR analysis revealed that expression of the FpOs1 gene was significantly altered in the resistant mutants in both the absence and presence of fludioxonil. Meanwhile, plate assays found evidence of cross-resistance between fludioxonil and cyprodinil, as well as with the triazole fungicides tebuconazole and difenoconazole, but not with other commonly used fungicides including prochloraz, fluazinam, and carbendazim. Taken together, these results provide new insights into the mechanism and biological characteristics associated with fludioxonil resistance in F. pseudograminearum and indicate that fludioxonil could provide effective and sustained control of FCR during wheat production.

Source Identification and Genome-Wide Association Analysis of Crown Rot Resistance in Wheat

Crown rot (CR) is a soil-borne disease of wheat in arid and semiarid areas of the world. The incidence rate and severity of CR are increasing with each passing year, which seriously threatens the safety of world wheat production. Here, 522 wheat varieties/lines representing genetic diversity were used to identify and evaluate the resistance source to CR disease. Six varieties, including Zimai 12, Xinong 509, Mazhamai, Sifangmai, and Dawson, were classified as resistant ® to CR. Seventy-nine varieties were classified as moderately resistant (MR) to CR, accounting for 15.13% of the tested varieties. The wheat 660 K SNP array was used to identify resistance loci by genome-wide association analysis (GWAS). A total of 33 SNPs, located on chromosomes 1A, 1B, 1D, 4A, and 4D, were significantly correlated with seedling resistance to CR in two years. Among them, one SNP on chromosome 1A and nine SNPs on chromosome 1B showed most significant resistance to disease, phenotypic variance explained (PVE) by these SNPs were more than 8.45%. Except that significant locus AX-110436287 and AX109621209 on chromosome 1B and AX-94692276 on 1D are close to the already reported QTL, other SNPs are newly discovered resistance loci. These results could lay a strong theoretical foundation for the genetic improvement and breeding for CR resistance in wheat.

Response of Fusarium pseudograminearum to Biocontrol Agent Bacillus velezensis YB-185 by Phenotypic and Transcriptome Analysis

The use of biological control agents (BCAs) is a promising alternative control measure for Fusarium crown rot (FCR) of wheat caused by Fusarium pseudograminearum. A bacterial strain, YB-185, was isolated from the soil of wheat plants with FCR and identified as Bacillus velezensis. YB-185 exhibited strong inhibition of F. pseudograminearum mycelial growth and conidial germination in culture. Seed treatment with YB-185 in greenhouse and field resulted in reductions in disease by 66.1% and 57.6%, respectively, along with increased grain yield. Microscopy of infected root tissues confirmed that YB-185 reduced root invasion by F. pseudograminearum. RNA-seq of F. pseudograminearum during co-cultivation with B. velezensis YB-185 revealed 5086 differentially expressed genes (DEGs) compared to the control. Down-regulated DEGs included genes for glucan synthesis, fatty acid synthesis, mechanosensitive ion channels, superoxide dismutase, peroxiredoxin, thioredoxin, and plant-cell-wall-degrading enzymes, whereas up-regulated DEGs included genes for chitin synthesis, ergosterol synthesis, glutathione S-transferase, catalase, and ABC transporters. In addition, fungal cell apoptosis increased significantly, as indicated by TUNEL staining, and the scavenging rate of 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS·+) in the fungus significantly decreased. Thus, F. pseudograminearum may be trying to maintain normal cell functions by increasing cell wall and membrane synthesis, antioxidant and anti-stress responses, detoxification of bacterial antimicrobial compounds, and transportation of damaging compounds from its cells. However, cell death and free radical accumulation still occurred, indicating that the responses were insufficient to prevent cell damage. Bacillus velezensis YB-185 is a promising BCA against FCR that acts by directly damaging F. pseudograminearum, thus reducing its ability to colonize roots and produce symptoms.

Deoxynivalenol Biosynthesis in Fusarium pseudograminearum Significantly Repressed by a Megabirnavirus

Deoxynivalenol (DON) is a mycotoxin widely detected in cereal products contaminated by Fusarium. Fusarium pseudograminearum megabirnavirus 1 (FpgMBV1) is a double-stranded RNA virus infecting Fusarium pseudograminearum. In this study, it was revealed that the amount of DON in F. pseudograminearum was significantly suppressed by FpgMBV1 through a high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS) assay. A total of 2564 differentially expressed genes were identified by comparative transcriptomic analysis between the FpgMBV1-containing F. pseudograminearum strain FC136-2A and the virus-free strain FC136-2A-V^-. Among them, 1585 genes were up-regulated and 979 genes were down-regulated. Particularly, the expression of 12 genes (FpTRI1, FpTRI3, FpTRI4, FpTRI5, FpTRI6, FpTRI8, FpTRI10, FpTRI11, FpTRI12, FpTRI14, FpTRI15, and FpTRI101) in the trichothecene biosynthetic (TRI) gene cluster was significantly down-regulated. Specific metabolic and transport processes and pathways including amino acid and lipid metabolism, ergosterol metabolic and biosynthetic processes, carbohydrate metabolism, and biosynthesis were regulated. These results suggest an unrevealing mechanism underlying the repression of DON and TRI gene expression by the mycovirus FpgMBV1, which would provide new methods in the detoxification of DON and reducing the yield loss in wheat.

Mode of action of nanochitin whisker against Fusarium pseudograminearum

Nanochitin whisker (NC) is an advanced nanobiomaterial with novel physicochemical and biological properties. Fusarium pseudograminearum (Fpg) is an important pathogenic fungus causing wheat crown rot disease. This study explored the mode of action of NC against Fpg as a target microorganism. The effects of different treatments and concentrations of NC on the fungal growth and conidial germination were investigated by in vitro bioassay. The impacts of NC on cell structure integrity, membrane permeability, pathogenesis related key enzymes activity, and the mycotoxin production were examined by electron microscopy, fluorescence spectroscopy, IR spectroscopy, conductometry, and spectrophotometry, respectively. The results showed that NC significantly reduced hyphal growth, and the spore germination rate of Fpg declined by 33.0 % and 23.2 % when Fpg was treated with 30 and 300 μg/mL of NC, respectively. NC vigorously influenced structural stability of cell wall by destroying dextran structure, and strongly stimulated ergosterol production altering membrane integrity of the fungus. It reduced the activities of enzymes related to energy-supply like nicotinamide adenine dinucleotide oxidase and succinate dehydrogenase remarkably. The production of fungal mycotoxin deoxynivalenol was also decreased by NC. These findings provide an important basis for fully understanding the mechanism of nanobiomaterial in plant fungal disease control.

Pest categorisation of Fusarium pseudograminearum

The EFSA Plant Health Panel performed a pest categorisation of Fusarium pseudograminearum O'Donnell & T. Aoki. F. pseudograminearum is a soil-borne fungal pathogen, able to cause a disease known as Fusarium crown rot (FCR, also known as foot and root rot) and occasionally Fusarium head blight on small grain cereals, particularly Triticum aestivum L., Triticum turgidum L. spp. durum (Dest.), Hordeum vulgare L. and triticale (xTriticosecale). In addition, F. pseudograminearum has been isolated from soybean (Glycine max L.) and from some grass genera, such as Phalaris, Agropyron and Bromus, which represent potentially important inoculum reservoirs. This pathogen has been reported in arid and semi-arid cropping regions in Australia, New Zealand, North and South America, northern Africa and South Africa, the Middle East and Asia. In the EU, it has been reported in Italy since 1994 and later in Spain on field-grown durum wheat, but uncertainty remains regarding the actual distribution of the pathogen in the EU. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. Seeds of host plants and soil and other substrates are the main pathways for the entry and spread of the pathogen into the EU. There are no reports of interceptions of F. pseudograminearum in the EU. Host availability and climate suitability occurring in the EU favour establishment of the pathogen and allow it to establish in areas from which it has not been reported. Phytosanitary measures are available to prevent the introduction of the pathogen into the EU, and additional measures are available to mitigate the risk of spread. In the non-EU areas of its present distribution, the pathogen has a direct impact on cultivated hosts (e.g. wheat, barley, triticale and soybean) that are also relevant for the EU. However, no crop losses have been reported so far in the EU. The Panel concludes that F. pseudograminearum satisfies all the criteria to be regarded as a potential Union quarantine pest.

Biocontrol of Wheat Crown Rot Using Bacillus halotolerans QTH8

Fusarium pseudograminearum causes crown rot in wheat. This study aimed to assess the effects of the bacterial strain QTH8 isolated from Cotinus coggygria rhizosphere soil against F. pseudograminearum. Bacterial strain QTH8 was identified as Bacillus halotolerans in accordance with the phenotypic traits and the phylogenetic analysis of 16S rDNA and gyrB gene sequence. Culture filtrates of bacterial strain QTH8 inhibited the mycelial growth of F. pseudograminearum and resulted in mycelial malformation such as tumor formation, protoplast condensation, and mycelial fracture. In addition, bacterial strain QTH8 also inhibited the mycelial growth of Hainesia lythri, Pestalotiopsis sp., Botrytis cinerea, Curvularia lunata, Phyllosticta theaefolia, Fusarium graminearum, Phytophthora nicotianae, and Sclerotinia sclerotiorum. The active compounds produced by bacterial strain QTH8 were resistant to pH, ultraviolet irradiation, and low temperature, and were relatively sensitive to high temperature. After 4 h exposure, culture filtrates of bacterial strain QTH8—when applied at 5%, 10%, 15%, 20%, 25%, and 30%—significantly reduced conidial germination of F. pseudograminearum. The coleoptile infection assay proved that bacterial strain QTH8 reduced the disease index of wheat crown rot. In vivo application of QTH8 to wheat seedlings decreased the disease index of wheat crown rot and increased root length, plant height, and fresh weight. Iturin, surfactin, and fengycin were detected in the culture extract of bacterial strain QTH8 by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Bacterial strain QTH8 was identified for the presence of the ituC, bacA, bmyB, spaS, srfAB, fend, and srfAA genes using the specific polymerase chain reaction primers. B. halotolerans QTH8 has a vital potential for the sustainable biocontrol of wheat crown rot.

An Improved Inoculation Method to Detect Wheat and Barley Genotypes for Resistance to Fusarium Crown Rot

Fusarium crown rot (FCR), caused by Fusarium species, is a serious soilborne fungal disease in many wheat growing regions in the world. A reliable FCR assessment method is essential for germplasm screening and host resistance studies. Here, we report a new assay in which we inoculated wheat seedlings grown in a glasshouse for FCR by injecting spore suspensions into the seedling stems. The effects of inoculum concentration and injection time points on disease severity were investigated. Of different treatments, the injection of 10⁷ macroconidia/ml suspension at one leaf and one heart stage gave best results. A collection of 92 emmer-derived hexaploid bread wheats, 43 barley germplasms, and four wheat genotypes with known resistance levels to FCR was used to validate this new method. Repeatability of the two trials in the validation experiments was high (r = 0.97, P < 0.01). Two emmer-derived hexaploid bread wheat and three Chinese barley germplasms showed consistent resistance to FCR in multiple rounds of selection. The short timeframe of this assay for phenotypic screening makes it a valuable tool to eliminate germplasms with undesirable susceptibility to FCR at seedling stage before costly field assays.

Antagonistic Activity of Fungal Strains against Fusarium Crown Rot

The crown rot of wheat is a destructive soil-borne pathogen that severely reduces the yield and quality of wheat. This study aimed to screen and identify the antagonistic strains against Fusarium pseudograminearum (Fp), which is the dominant pathogen associated with the crown rot of wheat in China, and evaluate their biosynthetic potential. The antagonistic strains were screened via a dual-culture antagonism assay, and then identified by combining the morphological characteristics and internal transcribed spacer gene sequencing. The polyketide synthases (PKS-I and PKS-II) and non-ribosomal peptide synthetase (NRPS) genes in the antagonistic strains were detected via specific amplification of chromosomal DNA. Eleven out of 157 fungal strains, including six strains with matrix competition and five strains with antibiosis, were obtained. The eleven antagonistic strains belonged to the following four genera: Alternaria, Botryosphaeria, Phoma and Talaromyces. The inhibition rate of six strains with matrix competition was greater than 50%, with B. dothidea S2-22 demonstrating the highest at 80.3%. The width of the inhibition zone of T. trachyspermus R-17 among the five strains with antibiosis was the widest at 11 mm. Among the eleven antagonistic strains, three strains of A. alternata and the strain P. moricola only contained the PKS-II gene, the strain A. tenuissima contained PKS-I and PKS-II genes, three strains of B. dothidea contained PKS-II and NRPS genes, while three strains of T. trachyspermus did not contain any genes. These results demonstrated potential strains for the biocontrol of the crown rot of wheat. In particular, T. trachyspermus R-17 can be investigated further as a promising agent, and the active substances secreted by antagonistic strains may be synthesized by other pathways.

Genome-wide association mapping of Fusarium crown rot resistance in Aegilops tauschii

Fusarium crown rot (FCR), caused by various Fusarium species, is a primary fungal disease in most wheat-growing regions worldwide. A. tauschii, the diploid wild progenitor of the D-genome of common wheat, is a reservoir of genetic diversity for improving bread wheat biotic and abiotic resistance/tolerance. A worldwide collection of 286 A. tauschii accessions was used to evaluate FCR resistance. Population structure analysis revealed that 115 belonged to the A. tauschii ssp. strangulata subspecies, and 171 belonged to the A. tauschii ssp. tauschii subspecies. Five accessions with disease index values lower than 20 showed moderate resistance to FCR. These five originated from Afghanistan, China, Iran, Uzbekistan, and Turkey, all belonging to the tauschii subspecies. Genome-wide association mapping using 6,739 single nucleotide polymorphisms (SNPs) revealed that two SNPs on chromosome 2D and four SNPs on chromosome 7D were significantly associated with FCR resistance. Almost all FCR resistance alleles were presented in accessions from the tauschii subspecies, and only 4, 11, and 19 resistance alleles were presented in accessions from the strangulata subspecies. Combining phenotypic correlation analysis and genome-wide association mapping confirmed that FCR resistance loci were independent of flowering time, heading date, and plant height in this association panel. Six genes encoding disease resistance-related proteins were selected as candidates for further validation. The identified resistant A. tauschii accessions will provide robust resistance gene sources for breeding FCR-resistant cultivars. The associated loci/genes will accelerate and improve FCR in breeding programs by deploying marker-assisted selection.

Contamination and Translocation of Deoxynivalenol and Its Derivatives Associated with Fusarium Crown Rot of Wheat in Northern China

Fusarium crown rot (FCR) is one of the most important wheat diseases in northern China. The main causal agent of FCR, Fusarium pseudograminearum, can produce mycotoxins such as type B trichothecenes. Therefore, FCR could be an additional source of mycotoxin contamination during wheat production. Field inoculation experiments demonstrated that FCR disease severity strongly impacts the distribution pattern of trichothecenes in different wheat tissues. Mycotoxins were mainly observed in lower internodes, and a low amount was detected in the upper parts above the fourth internode. However, high levels of trichothecene accumulation were detected in the upper segments of wheat plants under field conditions, which would threaten the feed production. The variation of mycotoxin content among sampling sites indicated that besides disease severity, other factors like climate, irrigation, and fungicide application may influence the mycotoxin accumulation in wheat. A comprehensive survey of deoxynivalenol (DON) and its derivatives in wheat heads with FCR symptoms in natural fields was conducted at 80 sites in seven provinces in northern China. Much higher levels of mycotoxin were observed compared with inoculation experiments. The mycotoxin content varied greatly among sampling sites, but no significant differences were observed if compared at province level, which indicated the variation is mainly caused by local conditions. Trace amounts of mycotoxin appeared to be translocated to grains, which revealed that FCR infection in natural fields poses a relatively small threat to contamination of grains but a larger one to plant parts that may be used as animal feed. To our knowledge, this is the first report of trichothecene accumulation in wheat stems and heads, as well as grains after FCR infection in natural field conditions. These investigations provide novel insights into food and feed safety risk caused by FCR in northern China.

Effects of Long-Term Bare Fallow During the Winter-Wheat Growth Season on the Soil Chemical Properties, Fungal Community Composition, and the Occurrence of Maize Fungal Diseases in North China

On the North China Plain, one of the most water-deficient regions in China, bare fallow has been implemented over a large-scale area to conserve water during the growth season of water-intensive winter wheat since 2015. However, the effects of this bare fallow on fungal community and the occurrence of crop diseases are poorly understood. Here we measured soil chemical properties, fungal community composition, and the occurrence of crop diseases after 15 years of long-term fallow (continuous maize or soybean) and non-fallow (maize-wheat rotation; soybean-wheat rotation) cropping systems. Bare fallow during the winter-wheat growth season significantly decreased soil organic matter, available nitrogen, and phosphorus. It also changed the composition of soil fungal communities, i.e., increased relative abundances of some potentially pathogenic species of Lectera, Fusarium, and Volutella but decreased beneficial Cladorrhium and Schizothecium. Meanwhile, the epidemic tendency of maize diseases changed correspondingly: the disease index of southern corn leaf blight and maize brown spot increased, but the incidence of stalk rot decreased compared with the non-fallow system. Soybean diseases were very mild regardless of the cropping system during the total experimental period. Network analysis demonstrated that the soil fungal diversity associated with maize diseases was affected by the decreased soil organic matter and available nitrogen and phosphorus. Our results suggest that bare fallow in the winter-wheat season affected the soil chemical properties, fungal community, and the occurrence of maize fungal diseases.

Heat Stress Tolerance Gene FpHsp104 Affects Conidiation and Pathogenicity of Fusarium pseudograminearum

Heat shock protein Hsp104, a homolog of the bacterial chaperone ClpB and plant Hsp100, plays an essential part in the response to heat and various chemical agents in Saccharomyces cerevisiae. However, their functions remain largely unknown in plant fungal pathogens. Here, we report the identification and functional characterization of a plausible ortholog of yeast Hsp104 in Fusarium pseudograminearum, which we termed FpHsp104. Deletion mutant of FpHsp104 displayed severe defects in the resistance of heat shock during F. pseudograminearum mycelia and conidia when exposed to extreme heat. We also found that the protein showed dynamic localization to small particles under high temperature. However, no significant differences were detected in osmotic, oxidative, or cell wall stress responses between the wild-type and Δfphsp104 strains. Quantitative real-time PCR analysis showed that FpHsp104 was upregulated in the conidia, and disruption of FpHsp104 gene resulted in defects in conidia production, morphology, and germination. The transcript levels of conidiation-related genes of FpFluG, FpVosA, FpWetA, and FpAbaA were reduced in the Δfphsp104 mutant vs. the wild-type strain, but heat-shocked mRNA splicing repair was not affected in Δfphsp104. Moreover, Δfphsp104 mutant also showed attenuated virulence, but its DON synthesis was normal. These data from the first study of Hsp104 in F. pseudograminearum strongly suggest that FpHsp104 gene is an important element in the heat tolerance, development, and pathogenicity processes of F. pseudograminearum.

TMT-based quantitative proteomic analysis reveals defense mechanism of wheat against the crown rot pathogen Fusarium pseudograminearum

BACKGROUND

Fusarium crown rot is major disease in wheat. However, the wheat defense mechanisms against this disease remain poorly understood.

RESULTS

Using tandem mass tag (TMT) quantitative proteomics, we evaluated a disease-susceptible (UC1110) and a disease-tolerant (PI610750) wheat cultivar inoculated with Fusarium pseudograminearum WZ-8A. The morphological and physiological results showed that the average root diameter and malondialdehyde content in the roots of PI610750 decreased 3 days post-inoculation (dpi), while the average number of root tips increased. Root vigor was significantly increased in both cultivars, indicating that the morphological, physiological, and biochemical responses of the roots to disease differed between the two cultivars. TMT analysis showed that 366 differentially expressed proteins (DEPs) were identified by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment in the two comparison groups, UC1110_3dpi/UC1110_0dpi (163) and PI610750_3dpi/PI610750_0dpi (203). It may be concluded that phenylpropanoid biosynthesis (8), secondary metabolite biosynthesis (12), linolenic acid metabolites (5), glutathione metabolism (8), plant hormone signal transduction (3), MAPK signaling pathway-plant (4), and photosynthesis (12) contributed to the defense mechanisms in wheat. Protein-protein interaction network analysis showed that the DEPs interacted in both sugar metabolism and photosynthesis pathways. Sixteen genes were validated by real-time quantitative polymerase chain reaction and were found to be consistent with the proteomics data.

CONCLUSION

The results provided insight into the molecular mechanisms of the interaction between wheat and F. pseudograminearum.

Analysis of Apoptosis-Related Genes Reveals that Apoptosis Functions in Conidiation and Pathogenesis of Fusarium pseudograminearum

The plant-pathogenic fungus F. pseudograminearum is the causal agent of Fusarium crown rot (FCR) in wheat and barley, resulting in substantial yield losses worldwide. Particularly, in the Huanghuai wheat-growing region of China, F. pseudograminearum was reported as the dominant Fusarium species in FCR infections.

Apoptosis, a type of programmed cell death, plays crucial roles in various physiological processes, from development to adaptive responses. Key features of apoptosis have been verified in various fungal microbes but not yet in Fusarium species. Here, we identified 19 apoptosis-related genes in Fusarium pseudograminearum using a genome-wide survey. Expression profile analysis revealed that several apoptosis-related genes were significantly increased during conidiation and infection stages. Among these is FpBIR1, with two BIR (baculovirus inhibitor-of-apoptosis protein repeat) domains at the N-terminal end of the protein, a homolog of Saccharomyces cerevisiae BIR1, which is a unique apoptosis inhibitor. FpNUC1 is the ortholog of S. cerevisiae NUC1, which triggers AIF1- or YCA1-independent apoptosis. The functions of these two proteins were assessed by creating Δfpbir1 and Δfpnuc1 mutants via targeted gene deletion. The Δfpbir1 mutant had more cells with nuclear fragmentation and exhibited reduced conidiation, conidial formation, and infectivity. Correspondingly, the Δfpnuc1 mutant contained multiple nuclei, produced thicker and more branched hyphae, was reduced in conidiation, and exhibited faster conidial formation and higher infection rates. Taken together, our results indicate that the apoptosis-related genes FpBIR1 and FpNUC1 function in conidiation, conidial germination, and infection by F. pseudograminearum.

IMPORTANCE The plant-pathogenic fungus F. pseudograminearum is the causal agent of Fusarium crown rot (FCR) in wheat and barley, resulting in substantial yield losses worldwide. Particularly, in the Huanghuai wheat-growing region of China, F. pseudograminearum was reported as the dominant Fusarium species in FCR infections. Apoptosis is an evolutionarily conserved mechanism in eukaryotes, playing crucial roles in development and cell responses to biotic and abiotic stresses. However, few reports on apoptosis in plant fungal pathogens have been published. In this study, we identified 19 conserved apoptosis-related genes in F. pseudograminearum, several of which were significantly increased during conidiation and infection stages. Potential apoptosis functions were assessed by deletion of the putative apoptosis inhibitor gene FpBIR1 and apoptosis trigger gene FpNUC1 in F. pseudograminearum. The FpBIR1 deletion mutant exhibited defects in conidial germination and pathogenicity, whereas the FpNUC1 deletion mutant experienced faster conidial formation and higher infection rates. Apoptosis appears to negatively regulate the conidial germination and pathogenicity of F. pseudograminearum. To our knowledge, this study is the first report of apoptosis contributing to infection-related morphogenesis and pathogenesis in F. pseudograminearum.

The Wheat Wall-Associated Receptor-Like Kinase TaWAK-6D Mediates Broad Resistance to Two Fungal Pathogens Fusarium pseudograminearum and Rhizoctonia cerealis

The soil-borne fungi Fusarium pseudograminearum and Rhizoctonia cerealis are the major pathogens for the economically important diseases Fusarium crown rot (FCR) and sharp eyespot of common wheat (Triticum aestivum), respectively. However, there has been no report on the broad resistance of wheat genes against both F. pseudograminearum and R. cerealis. In the current study, we identified TaWAK-6D, a wall-associated kinase (WAK) which is an encoding gene located on chromosome 6D, and demonstrated its broad resistance role in the wheat responses to both F. pseudograminearum and R. cerealis infection. TaWAK-6D transcript induction by F. pseudograminearum and R. cerealis was related to the resistance degree of wheat and the gene expression was significantly induced by exogenous pectin treatment. Silencing of TaWAK-6D compromised wheat resistance to F. pseudograminearum and R. cerealis, and repressed the expression of a serial of wheat defense-related genes. Ectopic expression of TaWAK-6D in Nicotiana benthamiana positively modulated the expression of several defense-related genes. TaWAK-6D protein was determined to localize to the plasma membrane in wheat and N. benthamiana. Collectively, the TaWAK-6D at the plasma membrane mediated the broad resistance responses to both F. pseudograminearum and R. cerealis in wheat at the seedling stage. This study, therefore, concludes that TaWAK-6D is a promising gene for improving wheat broad resistance to FCR and sharp eyespot.

Fusaristatin A production negatively affects the growth and aggressiveness of the wheat pathogen Fusarium pseudograminearum

Fusarium pseudograminearum (Fp), the causative fungal pathogen of the diseases Fusarium crown rot, is an important constraint to cereals production in many countries including Australia. Fp produces a number of secondary metabolites throughout its life cycle. One of these metabolites, the cyclic lipopeptide fusaristatin A, is encoded by a specific gene cluster containing a polyketide synthase and a three-module non-ribosomal peptide synthetase. However, a recent survey of Fp populations across Australia suggests that this cluster may only be present in a subset of isolates from Western Australia (WA). In this study, we screened 319 Fp isolates from WA and 110 Fp isolates from the Australian eastern states of New South Wales, Victoria, Queensland and South Australia to examine the distribution of this gene cluster among Australian Fp populations. The fusaristatin A gene cluster was found to be present in ~50% of Fp isolates from WA but completely absent in Fp isolates from eastern states. To determine its potential function, mutants of the fusaristatin A gene cluster were generated by disrupting the non-ribosomal peptide synthetase and polyketide synthase genes simultaneously in two different parental backgrounds. The mutants showed increased growth rates and were significantly more aggressive than their respective parental strains on wheat in crown rot pathogenicity assays. This suggested that fusaristatin A has a negative effect on fungal development and aggressiveness. The possible reasons for the geographically restricted presence of the fusaristatin A gene cluster and its role in fungal biology are discussed.

FpDep1, a component of Rpd3L histone deacetylase complex, is important for vegetative development, ROS accumulation, and pathogenesis in Fusarium pseudograminearum

Histone deacetylases (HDACs) play essential roles in modulating chromatin structure to provide accessibility to gene regulators. Increasing evidence has linked HADCs to pathogenesis control in the filamentous plant fungi. However, its function remains unclear in Fusarium pseudograminearum, which has led to the emergence of the disease Fusarium crown rot in China. Here we identified the FpDEP1 gene, an orthologue of Saccharomyces cerevisiae DEP1 encoding a component of the Rpd3 histone deacetylase complex in F. pseudograminearum. The gene deletion mutant, ΔFpdep1, showed significantly retarded growth on PDA plates with reduced aerial hyphae formation. Pathogenicity tests displayed no typical leaf lesions and limited expansion capability of coleoptiles. Histopathological analysis indicated the ΔFpdep1 deletion mutant differentiated infectious hyphae and triggered massive reactive oxygen species (ROS) accumulation during the early infection stage, resulting in limited expansion to neighbor cells which was concurring with sensitivity to H₂O₂ and SDS tests in vitro. FM4-64 staining revealed that the ΔFpdep1 deletion mutant was delayed in endocytosis. The FpDEP1-GFP transgene complemented the mutant phenotypes and the fusion protein co-localized with DAPI staining, indicating that the FpDEP1 gene product is localized to the nucleus in spores and mycelia. Immunoprecipitation coupled with LC-MS/MS and yeast two-hybrid screening identified the Rpd3L-like HDAC complex containing at least FpDep1, FpSds3, FpSin3, FpRpd3, FpRxt3, FpCti6, FpRho23, and FpUme6. These results suggest that FpDep1 is involved in a HDAC complex functioning on fungal development and pathogenesis in F. pseudograminearum.