Abstract
Nowadays, microorganisms that display plant growth promoting properties are significantly interesting for their potential role in reducing the use of chemical fertilizers. This research study proposed the isolation of the actinobacteria associated with arbuscular mycorrhizal fungi (AMF) spores and the investigation of their plant growth promoting properties in the in vitro assay. Three actinobacterial strains were obtained and identified to the genus Streptomyces (GETU-1 and GIG-1) and Amycolatopsis (GLM-2). The results indicated that all actinobacterial strains produced indole-3-acetic acid (IAA) and were positive in terms of siderophore, endoglucanase, and ammonia productions. In the in vitro assay, all strains were grown in the presence of water activity within a range of 0.897 to 0.998, pH values within a range of 5–11, and in the presence of 2.5% NaCl for the investigation of drought, pH, and salt tolerances, respectively. Additionally, all strains were able to tolerate commercial insecticides (propargite and methomyl) and fungicides (captan) at the recommended dosages for field applications. Only, Amycolatopsis sp. GLM-2 showed tolerance to benomyl at the recommended dose. All the obtained actinobacteria were characterized as plant growth promoting strains by improving the growth of chili plants (Capsicum flutescens L.). Moreover, the co-inoculation treatment of the obtained actinobacteria and AMF (Claroideoglomus etunicatum) spores could significantly increase plant growth, contribute to the chlorophyll index, and enhance fruit production in chili plants. Additionally, the highest value of AMF spore production and the greatest percentage of root colonization were observed in the treatment that had been co-inoculated with Streptomyces sp. GETU-1.
Highlights
Three actinobacteria associated with arbuscular mycorrhiza fungal (AMF) spores were isolated and identified
All the obtained actinobacterial strains were characterized as plant growth promoting microorganisms (PGPMs) and were capable of producing indole-3-acetic acid (IAA), siderophores, endoglucanase, and ammonia by the in vitro assay
Our findings indicate that the co-inoculation of Streptomyces sp
Summary
Chili (Capsicum annuum L.) is a commercially important plant that has considerable economic value as an agricultural crop. There has been an increase in demand for this plant in Thailand and throughout the world. Chili fruit contains numerous nutrients, vitamins, and minerals, and possesses a number of other health-promoting bioactive compounds that are known to be beneficial to humans [1,2]. Organization Statistical Database (FAOSTAT) reported that Indonesia was the largest chili producer in Southeast Asia followed by Malaysia, the Philippines, and Thailand. The trend to increase chili production in Thailand is expected to continue to grow in the future. Over a number of years, many chemical fertilizers have been used in the
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