Trichoderma drives soil fungal interactions against Fusarium wilt

Wood mold drives soil fungal interactions to resist wilt disease.

Microbial communities are widely present in the environment, covering almost all host surfaces, from the skin, intestines, and mucous membranes of animals to the roots and leaves of plants. These microorganisms form the first line of defense against pathogen invasion. However, outbreaks caused by harmful microorganisms can lead to significant damage to microbial populations, resulting in an increased incidence of diseases. Restoring or enhancing the natural defense provided by host-associated microbial communities can provide effective means for disease control.

The regulation of the microbiome can enhance the functionality of agricultural ecosystems and effectively suppress soil-borne diseases. Numerous studies have shown a direct correlation between the diversity and composition of soil microbiota and the suppression of soil-borne diseases. Rich microbial diversity can enhance the complexity of microbial interactions, thereby improving their resistance to pathogens. Considering the complexity of plant-microbe and microbe-microbe interactions, as well as the dependence of these interactions on environmental factors, optimizing the plant-microbe relationship remains a challenging task. Therefore, a better understanding of the interactions between beneficial microbes, pathogens, and soil microbiota is essential for effective disease control. However, little is currently known about how fungal communities are influenced by beneficial microbes and how fungal population dynamics affect disease control. Recently, there has been increasing interest in the role of fungi in environmental and host-associated microbiomes, but more attention is still needed regarding the impact of fungi on soil ecological functions and their role in disease suppression. The research article "Additive fungal interactions drive biocontrol of Fusarium wilt disease" by the team led by Academician Qi-Rong Shen from Nanjing Agricultural University was published in the internationally renowned academic journal New Phytologist. This study investigated the impact of the Trichoderma guizhouense NJAU4742 (Tg) biofertilizer on disease development in a continuous banana cropping system through a series of experiments.

Research found that after three consecutive seasons of banana cultivation, compared with the control group, the application of organic matter with or without inoculation of Trichoderma asperellum strain Tg (SOF+Tg and SOF) can effectively reduce the incidence of wilt disease and increase the biomass of banana plants. The disease prevention and growth promotion effects of the SOF+Tg treatment group were higher than those of the SOF treatment alone, with an average increase of 59.09% and 60.47%, respectively. In each planting season, compared with the other two treatments, the SOF+Tg treatment had the highest biomass and the lowest disease incidence. In the third growth season, the disease prevention effect of the SOF+Tg treatment reached 72.2±3.9%, and the growth promotion effect was 76.4±8.5%. The dynamic changes in the microbial community composition of the soil continuously planted for three seasons were analyzed. It was found that the fungal abundance in the SOF+Tg treatment group was significantly higher than that in the blank control, and the abundance of Fusarium in the SOF+Tg treatment was significantly lower than that in the SOF and CK treatments. Further analysis showed significant differences in the fungal community composition between the initial soil (before planting), control soil, SOF soil, and SOF+Tg soil. The relative abundance of Zygomycota and Glomeromycota in the initial soil was significantly higher than that in the control, SOF soil, and SOF+Tg soil. Compared with the initial soil and other treatments, CK and SOF significantly increased the relative abundance of Basidiomycota and Ascomycota, respectively. Compared with the initial soil, control soil, and SOF soil, the SOF+Tg treatment significantly reduced the relative abundance of Fusarium, while the relative abundance of Fusarium was highest in the initial soil. There were significant differences in soil microbial carbon metabolism capacity among CK, SOF, and SOF+Tg treatments. The SOF+Tg treatment significantly increased soil microbial carbon metabolism, with an increase of 23.98% and 38.91% compared to CK and SOF treatments, respectively.

Graph 1: Biomass of banana plants and incidence rate of Fusarium wilt disease.

Increasing the vaccination volume of Tg significantly improves the population density of the fungus and the proportion of Tg in the fungal community. Pot experiments have found that the application of Tg significantly affects the composition of the Humicola group in the fungal community. Applying wood mold can reduce the disease incidence of bananas by 72% and increase banana biomass. This effect is attributed to changes in the fungal microbiome, including a decrease in the density of Trichoderma and the enrichment of the antifungal fungus Humicola. The study has demonstrated the role of the wood mold-Humicola complex in disease control, and the overlapping ecological niche with the pathogen and the induction of plant systemic resistance may be one of the main mechanisms driving the biocontrol effect. In addition, Tg and Humicola can significantly increase the content of jasmonic acid and salicylic acid in banana plants. It was also found that the defense system of banana plants is more sensitive to co-inoculation with Tg and Humicola, indicating that these two fungi may jointly induce plant resistance through the JA and SA signaling pathways. Furthermore, the combination of Tg and Humicola has a greater activating effect on ISR-related enzyme activities in banana plants, such as chitinase (CHT), peroxidase (POD), phenylalanine ammonia-lyase (PAL), lipoxygenase (LOX), and polyphenol oxidase (PPO), compared to single fungi. The authors have demonstrated that the interaction with the indigenous microbial community may have a greater impact on disease suppression than the direct antagonistic effect of inoculated biocontrol agents.

Research on the induction of plant systemic resistance by fungal communities (Figure 2).

This study elucidates the inhibitory effect of fungal probiotics on natural diseases in a continuous banana monoculture system. The authors demonstrate the direct inhibitory effect of beneficial fungi on pathogens, as well as the indirect effects of their interaction with indigenous fungi in terms of nutrient competition and induction of plant systemic resistance, highlighting their value in disease control. The research results indicate that the application of fungal probiotics leads to the reshaping of soil fungal communities, recruiting beneficial fungal species to collectively resist pathogen invasion and protect plant health. These findings provide a new perspective for the development of effective and sustainable solutions to improve crop protection.