Figure 2 from the authors’ study, depicting Fusarium head blight (FHB) symptoms in wheat heads point inoculated with Fusarium graminearum ∆tri5 mutants and their respective parent strains. Spikelets of wheat cv. Norm were point-inoculated with a conidia suspension. Photographs were taken at 21 days postinoculation.
Newswise — Despite being one of the earliest cultivated food crops, wheat remains a significant staple in the global diet even after many millennia. Found on all continents except Antarctica, wheat ranks as the second most abundantly produced grain worldwide, yielding almost 800,000 metric tons annually (Food and Agriculture Organization). Nonetheless, Fusarium graminearum, a fungal pathogen, poses a severe threat by causing Fusarium head blight (FHB) on wheat, contaminating grains with harmful trichothecene toxins. One specific trichothecene, known as deoxynivalenol (DON), serves as a crucial virulence factor produced by the majority of F. graminearum strains in the United States. It amplifies the pathogen's propagation within a wheat head, endangering the economic stability of millions and the food security/safety of billions.
At present, there exists a lack of wheat (or barley) varieties that possess complete resistance against Fusarium infection, necessitating ongoing research on the virulence factors of Fusarium head blight (FHB). Recent scientific investigations have unveiled a population of F. graminearum that produces a novel trichothecene called NX, exhibiting a slightly distinct chemical composition compared to DON. Dr. Guixia Hao and colleagues from the USDA-Agricultural Research Service conducted a study aiming to elucidate the involvement of NX trichothecenes in FHB development in wheat, paralleling the role of DON. Published in the journal Molecular Plant-Microbe Interactions (MPMI), their findings demonstrate the significant contribution of NX trichothecenes in the initial infection of F. graminearum, as well as the subsequent spread of Fusarium head blight.
Through the deletion of the first gene involved in trichothecene biosynthesis, known as TRI5, from strains producing both DON trichothecenes and NX trichothecenes, the scientists were able to examine the severity of Fusarium head blight (FHB) on susceptible wheat heads. They inoculated these parent strains as well as the resulting genetic mutants lacking the TRI5 gene, and then assessed the outcomes. Subsequent evaluation and testing indicated that the NX-producing strain exhibited a higher level of toxin production compared to the DON-producing strain. These findings confirm that the deletion of the TRI5 gene eliminates the production of NX toxins and reduces both fungal infection and the spread of disease in wheat. Thus, it is established that NX, akin to DON, fulfills a similar role in the aggression of the pathogen, while uniquely intensifying the infection caused by the pathogen.
Dr. Hao's comment highlights the significance of the research findings, emphasizing the novelty of discovering a mycotoxin's role in enhancing both pathogen infection and disease spread in wheat heads. According to Dr. Hao, this study represents the first instance where a mycotoxin, which refers to any toxic substance produced by a fungus, has been identified to play such a pivotal role in wheat. This underscores the importance of the research and its contribution to advancing our understanding of the intricate dynamics between fungi, mycotoxins, and plant diseases.
The groundbreaking nature of this discovery holds particular excitement as it presents potential applications for safeguarding cereal grain crops in terms of both quantity and quality. Dr. Hao expresses the significance of the findings, stating that the newfound information offers a fresh approach to potentially controlling not just the symptoms but also the infection and spread of Fusarium head blight (FHB), as well as mycotoxin contamination. By targeting the fungus's ability to produce NX, it may be possible to simultaneously mitigate FHB infection, curb its spread, and prevent mycotoxin poisoning. Dr. Hao further explains that this study enhances our comprehension of how the fungus employs toxins as a novel weapon in its assault on plants. Ultimately, this research provides valuable insights for devising strategies to combat FHB and protect cereal grain crops.
The knowledge gained from this study serves as inspiration for future investigations into NX trichothecenes. Dr. Hao and her colleagues are currently engaged in a follow-up study aimed at creating transgenic plants. These plants will utilize a technique called ribonucleic acid interference (RNAi) to specifically target the biosynthesis gene responsible for NX production. By employing RNAi, the objective is to reduce both disease severity and mycotoxin production associated with Fusarium head blight (FHB). This follow-up research has the potential to contribute further to the development of innovative strategies for combating FHB and minimizing the harmful effects of mycotoxins in crops.
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