Microbacterium thalassium VALIDK02: an indole-3-acetic-acid producing endophyte of Capsicum frutescens as a promising biofertilizer for agricultural applications

Abstract This study aims to isolate the bacterial endophytes of Capsicum frutescens (Chilli) and investigate their impact on plant growth, health, and stress resistance via production of Indole-3-Acetic Acid (IAA). The surface sterilized roots of Capsicum frutescens were subjected for spread-plate method on a Luria-Bertani (LB) Agar plate to isolate endophytic bacteria. Obtained pure cultures of endophytic bacteria were screened for their ability to produce IAA using Salkowski’s method. The isolate that was positive for IAA production was subjected for morphological, biochemical and molecular characterization. The IAA producing bacterial endophyte was identified as Gram’s positive bacilli - Microbacterium thalassium. The 16 S rDNA sequence of Microbacterium thalassium VALIDK02 was submitted to GenBank with a GenBank ID PP851914. Further, Liquid Chromatography Mass Spectrometry (LC-MS) analysis of the cell-free-culture-supernatant confirmed the presence of IAA at a significantly high concentration of 6.07%. This ability to produce IAA in large proportion suggests that, the isolate is a strong candidate for biofertilizer applications to improve agricultural productivity. However, further field investigations are in demand to understand the in-situ effect of the isolate on plant growth and agricultural yield. The results of this study concludes that Microbacterium thalassium VALIDK02 an endophytic bacteria of Capsicum frutescens is a promising candidate for biofertilizer applications, based on its ability to produce significant concentration of plant-growth-promoting-hormone IAA.