Unveiling novel Neocosmospora species from Thai mangroves as potent biocontrol agents against Colletotrichum species.

AIMS: Neocosmospora species are saprobes, endophytes, and pathogens belonging to the family Nectriaceae. This study aims to investigate the taxonomy, biosynthetic potential, and application of three newly isolated Neocosmospora species from mangrove habitats in the southern part of Thailand using phylogeny, bioactivity screening, genome sequencing, and bioinformatics analysis. METHODS AND RESULTS: Detailed descriptions, illustrations, and a multi-locus phylogenetic tree with large subunit ribosomal DNA (LSU), internal transcribed spacer (ITS), translation elongation factor 1-alpha (ef1-α), and RNA polymerase II second largest subunit (RPB2) regions showing the placement of three fungal strains, MFLUCC 17-0253, MFLUCC 17-0257, and MFLUCC 17-0259 clustered within the Neocosmospora clade with strong statistical support. Fungal crude extracts of the new species N. mangrovei MFLUCC 17-0253 exhibited strong antifungal activity to control Colletotrichum truncatum CG-0064, while N. ferruginea MFLUCC 17-0259 exhibited only moderate antifungal activity toward C. acutatum CC-0036. Thus, N. mangrovei MFLUCC 17-0253 was sequenced by Oxford nanopore technology. The bioinformatics analysis revealed that 49.17 Mb genome of this fungus harbors 41 potential biosynthetic gene clusters. CONCLUSION: Two fungal isolates of Neocosmospora and a new species of N. mangrovei were reported in this study. These fungal strains showed activity against pathogenic fungi causing anthracnose in chili. In addition, full genome sequencing and bioinformatics analysis of N. mangrovei MFLUCC 17-0253 were obtained.

Xylaria feejeensis, SRNE2BP a Fungal Endophyte with Biocontrol Properties to Control Early Blight and Fusarium Wilt Disease in Tomato and Plant Growth Promotion Activity.

Over the past decade endophytic fungi have been known as a source of secondary metabolites with the ability to act as a biocontrol agents. Xylaria feejeensis, SRNE2BP a fungal endophyte isolated from a mangrove tree exhibited antagonistic activity against two fungal pathogens of tomato. Crude extract of X. feejeensis SRNE2BP significantly inhibited Fusarium oxysporum MFLUCC 19-0157 growth as shown approximately 60-75% in in vitro and in situ assays. Both assays showed that the endophyte also inhibited mycelium formation of Alternaria solani MFLUCC 19-0093 by 56% and 87%, respectively. The half maximal inhibitory concentration of X. feejeensis SRNE2BP crude extract against A. solani and F. oxysporum was approximately 7 mg/l. Crude extract and mycelium of X. feejeensis SRNE2BP showed potential in controlling early blight and fusarium wilt disease in tomato, respectively. Seedlings from seeds coated with crude extract of X. feejeensis SRNE2BP had lower disease severity (31.71%) of early blight disease compared to un-treated seeds (57.13%). Soil treated with 10% endophytic mycelium not only reduced fusarium wilt in tomato plant (55.55% severity compared with 91.66% in un-treated soil) but also promoted seed emergence and growth of tomato. Structure analysis revealed that 12 secondary metabolites, especially mellein derivatives, are major components of the crude extract of X. feejeensis SRNE2BP. These compounds could be responsible for antifungal activities; however, further study is required. Our findings strongly suggest that colonization with this fungal endophyte can be beneficial to the host plant especially with regards to plant growth promotion and broad antagonistic activity.

Napthoquinones from Neocosmospora sp.-Antibiotic Activity against Acidovorax citrulli, the Causative Agent of Bacterial Fruit Blotch in Watermelon and Melon.

Bacterial fruit blotch (BFB) is a bacterial disease that devastates Cucurbitaceae crops worldwide, causing significant economic losses. Currently, there is no means to treat or control the disease. This study focused on exploring the antibacterial properties of endophytic fungi against Acidovorax citrulli (Aac), the causative agent of BFB. Based on disc diffusion, time kill and MIC microdilution broth assays, four endophytes showed promise in controlling Aac. Nonetheless, only one strain, Neocosmospora sp. MFLUCC 17-0253, reduced the severity of disease on watermelon and melon seedlings up to 80%. Structure analysis revealed production of several compounds by the fungus. Three of these secondary metabolites, including mixture of 2-methoxy-6-methyl-7-acetonyl-8-hydroxy-1,4-maphthalenedione and 5,8-dihydroxy-7-acetonyl-1,4-naphthalenedione, anhydrojavanicin, and fusarnaphthoquinones B exhibited antagonistic activity against Aac. The chemical profile data in planta experiment analyzed by LC-Q/TOF-MS suggested successful colonization of endophytic fungi in their host plant and different metabolic profiles between treated and untreated seedling. Biofilm assay also demonstrated that secondary metabolites of Neocosmospora sp. MFLUCC 17-0253 significantly inhibited biofilm development of Aac. To the best of our knowledge, secondary metabolites that provide significant growth inhibition of Aac are reported for the first time. Thus, Neocosmospora sp. MFLUCC 17-0253 possesses high potential as a biocontrol agent for BFB disease.