Fusarium pseudograminearum is a devastating pathogen that causes Fusarium crown rot (FCR) in wheat and poses a significant threat to wheat production in terms of grain yield and quality. However, the mechanism by which F. pseudograminearum infects wheat remains unclear. In this study, we aimed to elucidate these mechanisms by constructing a T-DNA insertion mutant library for the highly virulent strain WZ-8A of F. pseudograminearum. By screening this mutant library, we identified nine independent mutants that displayed impaired pathogenesis in barley leaves. Among these mutants, one possessed a disruption in the gene FpRCO1 that is an ortholog of Saccharomyces cerevisiae RCO1, encoding essential component of the Rpd3S histone deacetylase complex in F. pseudograminearum. To further investigate the role of FpRCO1 in F. pseudograminearum, we employed a splitmarker approach to knock out FpRCO1 in F. pseudograminearum WZ-8A. FpRCO1 deletion mutants exhibit reduced vegetative growth, conidium production, and virulence in wheat coleoptiles and barley leaves, whereas the complementary strain restores these phenotypes. Moreover, under stress conditions, the FpRCO1 deletion mutants exhibited increased sensitivity to NaCl, sorbitol, and SDS, but possessed reduced sensitivity to H2O2 compared to these characteristics in the wild-type strain. RNA-seq analysis revealed that deletion of FpRCO1 affected gene expression (particularly the downregulation of TRI gene expression), thus resulting in significantly reduced deoxynivalenol (DON) production. In summary, our findings highlight the pivotal role of FpRCO1 in regulating vegetative growth and development, asexual reproduction, DON production, and pathogenicity of F . pseudograminearum. . This study provides valuable insights into the molecular mechanisms underlying F . pseudograminearum infection in wheat and may pave the way for the development of novel strategies to combat this devastating disease.

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.

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.