Development of a Rapid Sporulation Method of Fusarium graminearum Using Liquid Cultivation

Evaluation of Resistance Resources and Analysis of Resistance Mechanisms of Maize to Stalk Rot Caused by Fusarium graminearum

Stalk rot is one of the most destructive and widely distributed diseases in maize plants worldwide. Research on the performance and resistance mechanisms of maize against stem rot is constantly improving. In this study, among 120 inbred maize lines infected by Fusarium graminearum using the injection method, 4 lines (3.33%) were highly resistant to stalk rot, 28 lines (23.33%) were resistant, 57 lines (47.50%) were susceptible, and 31 lines (25.84%) were highly susceptible. The inbred lines 18N10118 and 18N10370 were the most resistant and susceptible with disease indices of 7.5 and 75.6, respectively. Treatment of resistant and susceptible maize inbred seedlings with F. graminearum showed that root hair growth of the susceptible inbred lines was significantly inhibited, and a large number of hyphae attached and adsorbed multiple conidia near the root system. However, the resistant inbred lines were delayed and inconspicuous, with only a few hyphae and spores appearing near the root system. Compared with susceptible inbred lines, resistant maize inbred line seedlings treated with F. graminearum exhibited elevated activities of catalase, phenylalanine ammonia-lyase, polyphenol oxidase, and superoxide dismutase. We identified 153 genes related to disease resistance by transcriptome analysis. The mitogen-activated protein kinase signaling and peroxisome pathways mainly regulated the resistance mechanism of maize inbred lines to F. graminearum infection. These two pathways might play an important role in the disease resistance mechanism, and the function of genes in the two pathways must be further studied, which might provide a theoretical basis for further understanding the molecular resistance mechanism of stalk rot and resistance gene mining.

Diverse mycotoxin threats to safe food and feed cereals

Toxigenic fungi, including Aspergillus and Fusarium species, contaminate our major cereal crops with an array of harmful mycotoxins, which threaten the health of humans and farmed animals. Despite our best efforts to prevent crop diseases, or postharvest spoilage, our cereals are consistently contaminated with aflatoxins and deoxynivalenol, and while established monitoring systems effectively prevent acute exposure, Aspergillus and Fusarium mycotoxins still threaten our food security. This is through the understudied impacts of: (i) our chronic exposure to these mycotoxins, (ii) the underestimated dietary intake of masked mycotoxins, and (iii) the synergistic threat of cocontaminations by multiple mycotoxins. Mycotoxins also have profound economic consequences for cereal and farmed-animal producers, plus their associated food and feed industries, which results in higher food prices for consumers. Climate change and altering agronomic practices are predicted to exacerbate the extent and intensity of mycotoxin contaminations of cereals. Collectively, this review of the diverse threats from Aspergillus and Fusarium mycotoxins highlights the need for renewed and concerted efforts to understand, and mitigate, the increased risks they pose to our food and feed cereals.

Synergy of cystamine and pyraclostrobin against Fusarium graminearum involves membrane permeability mitigation and autophagy enhancement

The application of fungicide mixture is one of the most important measures to extend the service life of highly selective fungicides. Pyraclostrobin (PYR), which has been extensively used to control plant diseases by inhibiting mitochondrial respiration of pathogenic fungi, is at a high risk of resistance development. In this study, the potential of PYR alone or in combination with cystamine, an inhibitor of microbial transglutaminase, to suppress Fusarium graminearum was tested in vitro and in vivo. A synergistic effect of PYR/CYS mixture was observed both in vitro and when applied to etiolated wheat coleoptile. The control effect of PYR/CYS mixture on F. graminearum was better than that of PYR alone, which was reflected by the increased protection effect. The discrepancies of membrane permeability and the redox-physiological state were observed between PYR and PYR/CYS treatments, suggesting that an increased PYR availability in F. graminearum mycelia could be related with the observed synergistic action. Moreover, a synergistic profile was observed between PYR and CYS in regard of massive autophagosomes in mycelia, indicating that enhanced autophagy could be involved in the mode of action of PYR/CYS mixture. The differential content of mitochondrial metabolites between PYR and PYR/CYS treatments also provided evidence for CYS contribution to the fungicidal action of PYR/CYS mixture. The results provide insight into the synergistic mechanism of action of PYR/CYS mixture and an effective way to enhance the efficiency of PYR to combat F. graminearum.