Aureobasidium sp. From cardamom plant as a potential biocontrol for Fusarium equiseti infecting tomato plants

Fusarium equiseti is an emerging phytopathogen causing increasing field and postharvest losses, particularly in smallholder farming systems. This study evaluated the biocontrol potential of Aureobasidium sp. BGP-C02, an endophytic isolate obtained from healthy cardamom ( Amomum subulatum Roxb.) leaves in eastern Nepal. Morphological traits and ITS rDNA analysis placed the isolate within the A. pullulans clade; however, due to limited marker resolution, it was conservatively designated as Aureobasidium sp. Antagonistic activity against F. equiseti was assessed using in vitro dual-culture assays, volatile organic compounds (VOCs) mediated inhibition, microscopic examination of hyphal morphology, and enzymatic profiling. Remarkably, BGP-C02 inhibited pathogen growth, induced hyphal abnormalities, and produced amylase and cellulase. Seed germination assays showed that preventive application effectively reduced disease incidence and severity, while curative treatment provided partial protection. Greenhouse experiments confirmed reduced disease incidence in biocontrol-treated plants. Under pathogen-free conditions, biocontrol treatment resulted in a numerical increase in shoot dry weight, although this difference was not statistically significant. Overall, Aureobasidium sp. BGP-C02 suppresses F. equiseti through multiple complementary mechanisms and represents a promising eco-friendly biocontrol candidate from an underexplored crop system.