Identification of Seed and Soil-Borne Fungal Disease Agents in Okra Plants (Abelmoschus esculentus L.) and Characterization of Biological Control Possibilities with Antagonist Bacterial Isolates

OpenAlex · İngilizce

The main objectives of this study were to (i) identify the seed- and soil-borne fungal pathogens of okra (Abelmoschus esculentus L.) grown in the Hatay province of Türkiye, (ii) determine the in vitro biocontrol potential of bacterial isolates (BCAs) from healthy okra and closely related plants against common fungal pathogens, and (iii) characterize the antagonistic and plant growth-promoting (PGP) mechanisms involved in pathogen suppression and plant growth. Rhizoctonia solani, Macrophomina phaseolina, Sclerotinia sclerotiorum, and Fusarium oxysporum were determined as the most common soil and seed-borne disease agents on diseased seeds and plants. A total of 36 different endophytic and epiphytic bacterial isolates were selected and identified using MALDI-TOF MS, and their antagonistic potentials to inhibit mycelial growth of R. solani, M. phaseolina, S. sclerotiorum, and F. oxysporum were characterized in dual culture tests. Among BCA bacterial isolates, Bacillus cereus B1ep, B. cereus B2ep, Pseudomonas aeruginosa B3ep, B. cereus B11ep, and B. subtilis B12ep displayed high levels (≥70%) of antagonistic activity against all fungal agents tested. Enterobacter cloacae B10ep was identified as the highest siderophore producer, Microbacterium maritypicum X5 as the highest protease enzyme producer, Pseudomonas aeruginosa B3ep, and different Bacillus spp. as isolates producing hydrogen cyanide (HCN) and ammonia at the highest level. The suppression of mycelial growth was suggested to be associated with one or more antagonistic mechanisms. Enterobacter bugandensis B7ep was identified as the highest Indole-3 Acetic Acid (IAA) producer, and B. cereus P7en was identified as the most efficient phosphate-solubilizing bacterial isolate. In conclusion, BCA isolates belonging to Bacillus and Pseudomonas spp., which demonstrated strong antagonistic and PGP activities, have the potential to be developed as biopreparations against soil and seed-borne disease agents in okra plants.