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Exploring Microbiome of Medicinal Plants as Biocontrol Agents

Gul Shad Ali: University of Florida

<div>Plant microbiome plays an important role in plant health and plant-environment interactions, but the microbiome of medicinal plant is less explored. In this report, endophytic bacteria were isolated from five different medicinal plants:<em>Cannabis sativa, Dodonaea viscosa, Fagonia indica, Caralluma tuberculata</em> and <em>Calendula arvensis. </em>On the basis of initial antimicrobial screening, 12 bacterial species that based on 16S rRNA gene sequencing belonged to nine different genera (<em>Serratia</em>, <em>Enterobacter</em>, <em>Paenibacillus</em>, <em>Streptomyces, Pseudomonas, Bacillus, Pantoea, Pseudarthrobacter </em>and <em>Delftia</em>) were selected for further analyses. Antimicrobial assays revealed that <em>E. cloacae, Paenibaillus </em>sp. and<em> P. taiwanensis</em> have strong anti-<em>Phytophthora </em>activity<em>. </em>Volatiles produced by<em> P. taiwanensis </em>inhibited growth of <em>P. parasitica </em>by more than 80%. Ethyl acetate extracts of <em>S. marcescens</em>, <em>E. cloacae</em>, <em>Paenibacillus</em> sp., <em>S. alboniger</em>, <em>P. taiwanensis</em><em>, E. hormaechei </em>and <em>B. tequilensis </em>and <em>D. lacustris</em> also displayed high potency against <em>P. </em><em>parasitica</em> at different concentrations (4 µg/mL – 400 µg/mL). Bacterial extracts showing with high bioactivity (>80% inhibition <em>in vitro</em>) were selected for detached-leaf assay against <em>P. parasitica</em>. In detached-leaf assay, application of 1% ethyl acetate bacterial extract of reduced lesion sizes and lesion frequencies caused by <em>P. parasitica </em>by 68 to 81%. Over all <em>P. taiwenensis</em> showed positive activities for all the assays. Analysing the potential of bacterial endophytes as biological control agents can potentially lead to the formulation of broad-spectrum biopesticides for agriculturally important crops.</div>