Isolation and in vitro Evaluation of Antagonistic Bacterial Endophytes from Eleusine coracana (L.) Gaertn. against Magnaporthe oryzae

Biocontrol potential of endophytic bacteria against a collection of Leptosphaeria maculans isolates causing blackleg in oilseed rape

Isolation and Characterization of Endophytic bacteria from Wedelia chinensis with Potent Biocontrol and Plant Growth-Promoting Activities

Endophytic bacteria represent a promising, sustainable alternative to synthetic agrochemicals for plant disease management by actively antagonizing phytopathogens and stimulating host immune responses. Despite its traditional use as an antimicrobial remedy, Wedelia chinensis remains underexplored as a source of beneficial endophytes. This study aimed to isolate and screen endophytic bacteria from W. chinensis for their antifungal activity against Fusarium oxysporum. Among 14 endophytic isolates, Bacillus subtilis LS1-5 showed the strongest antifungal activity by dual culture assay. Its cell-free culture filtrate effectively inhibited fungal spore germination by 91.3% at a 20% concentration. Crucially, B. subtilis LS1-5 produced several extracellular enzymes, including cellulase, amylase, chitinase, pectinase, gelatinase, lipase, and protease. Furthermore, the LS1-5 strain exhibited a broad array of plant growth-promoting and environmental resilience traits. Notably, it synthesized indole-3-acetic acid (IAA) at 2.11 ± 0.27 µg/mL in an LB medium without L-tryptophan, significantly promoted a 34.19% increase in root elongation, and demonstrated remarkable tolerance to extreme conditions, including high salinity (11% NaCl) and broad pH levels ranging from 6 to 12. Additionally, volatile organic compounds (VOCs) emitted by LS1-5 significantly inhibited the severe bacterial pathogens Xanthomonas oryzae (45.83%) and Xanthomonas citri (47.99%). These findings highlight B. subtilis LS1-5 as a highly effective candidate for biological control and sustainable agricultural applications.

Antagonistic and Plant Growth-Promoting Potential of Endophytic Trichoderma Against Fusarium Root Rot in Loquat (Eriobotrya japonica)

Loquat (Eriobotrya japonica) is highly susceptible to destructive soil-borne Fusarium pathogens, which cause severe vascular wilt and root rot. While Trichoderma species are widely applied as biocontrol agents, the potential of endophytic Trichoderma strains from loquat remains largely unexplored. This study aimed to isolate and evaluate loquat endophytic Trichoderma strains for their antifungal and plant growth-promoting capabilities. Ten isolates were identified through morphological and phylogenetic analyses as belonging to T. asperellum, T. virens and T. hamatum. Antagonistic activity was initially screened in vitro via dual-culture assays, followed by in vivo greenhouse pot experiments. In vitro results revealed that T. asperellum strains (B077R1 and B077B3) and T. virens GFR9 strongly inhibited the mycelial growth of both F. oxysporum and F. solani (inhibition rates > 50.65%), whereas T. hamatum isolates exhibited weaker antagonism (<35.18%). Moreover, T. asperellum B077R1 demonstrated the highest biocontrol efficacy in the greenhouse pot assay, significantly reducing disease severity caused by F. oxysporum and F. solani by 45.99% and 55.50%, respectively. This strain also significantly enhanced plant height, total biomass (fresh and dry weight) and photosynthetic pigment content (p < 0.05). These findings suggest that newly isolated endophytic Trichoderma strains from loquat exhibit robust host compatibility, offering a promising sustainable strategy for managing root rot in perennial fruit crops.

In vitro Antagonistic Efficacy of Trichoderma viride Culture Filtrates Against Sclerotium rolfsii Sacc., the Causal Agent of Groundnut Stem Rot

Groundnut (Arachis hypogaea L.) is an important oilseed crop, but its productivity is affected by stem rot caused by Sclerotium rolfsii Sacc. Biological control using antagonistic fungi offers a potential approach for reducing dependence on chemical disease management. The present study evaluated the in vitro inhibitory activity of cell-free culture filtrates from ten native isolates of Trichoderma viride against S. rolfsii. The pathogen was isolated from infected groundnut stem tissues and identified based on colony morphology and sclerotial characteristics. T. viride isolates were obtained from rhizosphere soil samples and maintained as Tv1 to Tv10. Culture filtrates were prepared from 10-day-old potato dextrose broth cultures and incorporated into potato dextrose agar at 10%, 20%, 30% and 40% concentrations using the poisoned food technique. All isolates reduced radial mycelial growth of S. rolfsii compared with the control and inhibition generally increased with filtrate concentration. Among the isolates tested, Tv4 showed the greatest inhibitory effect, restricting pathogen growth to 27.79 mm, 19.56 mm, 12.26 mm and 0.00 mm at 10%, 20%, 30% and 40% concentrations, respectively. Complete inhibition was observed with Tv4 at a 40% concentration. Tv6, Tv7 and Tv8 also showed high inhibition at the highest concentration. These results indicate that T. viride culture filtrates can suppress S. rolfsii growth under in vitro conditions.

Comparative Insights into Bacterial Endophytome and Antifungal Metabolites in Fusarium Wilt-Resistant and -Susceptible Banana Cultivars Unveil the Resistance Toward Fusarium oxysporum f. sp. cubense

India contributes 26% of global banana production, yet cultivation is severely threatened by Fusarium wilt (Fusarium oxysporum f. sp. cubense, Foc), necessitating sustainable, eco-friendly management strategies. This study evaluated the biocontrol potential of endophytic bacteria isolated from Foc-resistant and -susceptible banana cultivars. Isolates from the pseudostem, corm, and root of the resistant cultivar showed significantly greater inhibitory activity than those from the susceptible cultivar, underscoring the role of host genotype in shaping functionally competent endophytic communities. Among all isolates, Bacillus sp. from the corm of cv. Rose (AB) showed the highest mycelial inhibition of Foc (70.37–76.54%) in vitro. GC-MS-based metabolite profiling revealed a chemically diverse array of secondary metabolites, fatty acid esters, steroids, terpenoids, siloxanes, and nitrogenous compounds. Corm-associated endophytes exhibited membrane-disruptive and cytotoxic activity, while root-associated endophytes contributed protective, defense-modulatory effects. Halomonas sp. RoRo2 and B. subtilis RoC1 showed the highest inhibition in both agar-well and in planta assays, with unsaturated fatty acids and organic acid derivatives implicated as key antifungal effectors acting through multiple biochemical pathways. These findings identify metabolically versatile endophytes as promising candidates for developing efficient, environmentally compatible bioinoculants as sustainable alternatives to chemical control of Fusarium wilt in banana.

Screening and Characterization of Native Microbial Antagonists for the Development of a Multi-Strain Biocontrol Consortium against Ralstonia solanacearum

Bacterial wilt caused by Ralstonia solanacearum remains difficult to manage sustainably, creating a need for compatible native microbial antagonists with complementary biocontrol traits. This study isolated four rhizosphere microorganisms—Trichoderma viride (Tv), Pseudomonas fluorescens (Pf), Bacillus subtilis (Bs) and Azotobacter chroococcum (Ac)—from healthy eggplant plants surviving in bacterial-wilt-affected fields and assessed their antagonistic, biochemical, plant-growth-associated and compatibility characteristics. In dual-culture assays, Pf showed the highest inhibition of R. solanacearum (68.50%; 18.40 mm inhibition zone), followed by Bs (55.40%; 15.60 mm). Hydrolytic enzyme screening indicated overlapping amylase, protease and lipase activities among the antagonists, with Bs showing a 16.5 mm protease clearance zone and Pf a 14.2 mm zone. Siderophore screening showed the largest CAS halo for Pf (22.40 mm), which also exhibited a strong positive reaction for HCN production. Ac produced the highest indole-3-acetic acid concentration (32.60 µg/ml), followed by Pf (28.40 µg/ml). Cross-streak assays showed no visible inter-strain inhibition among Tv, Pf, Bs and Ac under the tested conditions. These findings indicate complementary in vitro functional traits and preliminary mutual compatibility among the four isolates, supporting their further evaluation as candidate components of a multi-strain biocontrol consortium. Molecular identification, formulation assessment and greenhouse and field validation remain necessary before practical application.