Sabiha Ramadani, Douglas J. H. Shyu, Endrika Widyastuti, Christoper Caesar Yudho Sutopo, Jue-Liang Hsu
Latex-producing plants harbor unique microbial communities that may play important roles in host defense; however, their diversity and biocontrol potential remain largely unexplored. Characterizing these communities provides opportunities to identify novel microbial-derived antifungal agents for sustainable crop protection. Bacterial strains were isolated from the latex of Alstonia scholaris (L.) R. Br. and identified using 16S rRNA gene sequencing. Antifungal activity was evaluated against four phytopathogens: Fusarium graminearum, Colletotrichum musae, Colletotrichum gloeosporioides, and Glomerella cingulata. Bioassay-guided fractionation, size-exclusion chromatography, SDS-PAGE, and LC-MS/MS were used to characterize antifungal proteins. Nine bacterial strains were isolated, including eight Bacillus spp. and one Enterococcus faecalis. Among them, Bacillus sp. AsL-2 exhibited the strongest broad-spectrum antifungal activity, inhibiting fungal growth by up to 80%. The antifungal activity of its crude extract remained stable over a wide temperature range. Further characterization identified a novel endo-β-1,3-1,4-glucanase enzyme (~23 kDa) as the major antifungal protein. This study reveals A. scholaris latex as an underexplored microbial niche and identifies Bacillus sp. AsL-2, affiliated with the B. velezensis–B. amyloliquefaciens species complex, as a promising biocontrol candidate. The identified antifungal enzyme represents a potential natural alternative to synthetic fungicides for sustainable agricultural disease management. © 2026 by the authors.
Department of Agriculture and International Cooperation, National Pingtung University of Science and Technology, Pingtung, 91201, Taiwan; Department of Biological Science and Technology, National Pingtung University of Science and Technology, Pingtung, 91201, Taiwan; Department of Food Science and Biotechnology, Faculty of Agricultural Technology, Universitas Brawijaya, Malang, 65145, Indonesia; Department of Animal Science and Technology, National Taiwan University, Taipei, 106037, Taiwan
