Warin Intana, Nakarin Suwannarach, Jaturong Kumla, Prisana Wonglom, Anurag Sunpapao
Several strains of are applied in the field to control plant diseases due to their capacity to suppress fungal pathogens and control plant diseases. Some strains also are able to promote plant growth through the production of indole-3-acetic acid (IAA). In southern Thailand, the local rice variety "Chor Khing" is mainly cultivated in the Songkhla province; it is characterized by slow growth and is susceptible to sheath blight caused by . Therefore, this research aimed to screen species with the ability to promote plant growth in this rice variety and enact biological control against . A total of 21 isolates were screened for indole compound production using the Salkowski reagent. The Z2-03 isolate reacted positively to the Salkowski reagent, indicating the production of the indole compound. High-performance liquid chromatography (HPCL) confirmed that Z2-03 produced IAA at 35.58 ± 7.60 μg/mL. The cell-free culture filtrate of the potato dextrose broth (CF) of Z2-03 induced rice germination in rice seeds, yielding root and shoot lengths in cell-free CF-treated rice that were significantly higher than those of the control (distilled water and culture broth alone). Furthermore, inoculation with conidia promoted rice growth and induced a defense response against during the seedling stage. Z2-03 displayed an antifungal capacity against , achieving 74.17% inhibition (as measured through dual culture assay) and the production of siderophores on the CAS medium. The pot experiment revealed that inoculation with the sp. Z2-03 conidial suspension increased the number of tillers and the plant height in the "Chor Khing" rice variety, and suppressed the percentage of disease incidence (PDI). The isolate Z2-03 was identified, based on the morphology and molecular properties of ITS, translation elongation factor 1-alpha (), and RNA polymerase 2 (), as Z2-03. Our results reveal the ability of Z2-03 to act as a plant growth promoter, enhancing growth and development in the "Chor Khing" rice variety, as well as a biological control agent through its competition and defense induction mechanism in this rice variety.
