Effects of synthetic and environmentally friendly fungicides on powdery mildew management and the phyllosphere microbiome of cucumber

Abstract

Modern agricultural practices rely on synthetic fungicides to control plant disease, but the application of these fungicides has raised concerns regarding human and environmental health for many years. As a substitute, environmentally friendly fungicides have been increasingly introduced as alternatives to synthetic fungicides. However, the impact of these environmentally friendly fungicides on plant microbiomes has received limited attention. In this study, we used amplicon sequencing to compare the bacterial and fungal microbiomes in the leaves of powdery mildew-infected cucumber after the application of two environmentally friendly fungicides (neutralized phosphorous acid (NPA) and sulfur) and one synthetic fungicide (tebuconazole). The phyllosphere α-diversity of both the bacterial and fungal microbiomes showed no significant differences among the three fungicides. For phyllosphere β-diversity, the bacterial composition exhibited no significant differences among the three fungicides, but fungal composition was altered by the synthetic fungicide tebuconazole. While all three fungicides significantly reduced disease severity and the incidence of powdery mildew, NPA and sulfur had minimal impacts on the phyllosphere fungal microbiome relative to the untreated control. Tebuconazole altered the phyllosphere fungal microbiome by reducing the abundance of fungal OTUs such as Dothideomycetes and Sordariomycetes, which included potentially beneficial endophytic fungi. These results indicated that treatments with the environmentally friendly fungicides NPA and sulfur have fewer impacts on the phyllosphere fungal microbiome while maintaining the same control efficacy as the synthetic fungicide tebuconazole.

Phyllosphere Microbiome in Plant Health and Disease

“…Berg and Koskella (2018) showed that fertilization makes a plant more vulnerable to pathogen attacks [48]. A recent study revealed that the application of tebuconazole altered the fungal microbiome by decreasing the abundant fungal members, including the potentially beneficial endophytic fungi, while NPA (Neutralized Phosphorous Acid) and sulfur had minimal impacts on the phyllosphere fungal microbiome [49]. Urbanization leads to an increase in human activities and has a strong effect on the phyllosphere microbiota [50][51][52].…”

Effect of Bacterial Consortium and Rice Husk Charcoal to Control Downy Mildew in Corn (Zea mays L.)

“…However, the excessive use of synthetic fungicides can result in the emergence of novel strains and outbreaks within agricultural environments, thereby adding complexity to disease control efforts. Consequently, relying on synthetic fungicides over prolonged periods is not environmentally sustainable and may prove ineffective as a long-term strategy for mitigating downy mildew disease (Wu et al, 2023). The continued use of synthetic fungicides is known to have a negative impact on non-target organisms and the soil.…”

Green Biochemical Protection of Postharvest Table Grapes Against Gray Mold (Botrytis Cinerea) Using 7s Proteins

“…However, the long-term and extensive use of these chemicals resulted in myriad problems, such as, increased pathogen resistance, soil contamination, polluted environment, unsafe for health, and deteriorating ecological structures (Kautsky et al, 2000). Furthermore, the growing consumers' interest in organic fruits and their processed products is urging the search for safer alternatives to synthetic fungicides while reducing costs and protecting the environment (Wu et al, 2023).…”