Plant Growth Promoting Activity of Colletotrichum sp., an Endophyte of Helicteres isora L. and its Growth Optimization using Response Surface Methodology

Abstract

Endophytes are the beneficial group of plant symbionts and are potent sources for producing novel metabolites with biotechnological applications. They are efficient sources for the synthesis of plant growth-promoting substances- Indole acetic acid, ammonia, solubilizing phosphates and thus open up sustainable agricultural opportunities. In the present investigation, twenty-two fungal endophytes were isolated from an ethnomedicinal plant-Helicteres isora L., collected from forests of Singbhum, Jhargram, India, and the isolate-Colletotrichum sp. HelS1, exhibited the most potent in vitro plant growth-promoting activities among all. HelS1 synthesized auxin (111.13 µg ml-1), ammonia, and solubilized phosphate (47.22 µg ml-1) in specific culture conditions. A treatment with fungal extract effectively increases the growth of the experimental plant (tomato seedlings) in terms of improvement in relative water contents, dry weight, nodal length, and pigment profiles compared to the untreated ones. There was an increase in root length by 27% compared to the control group. The isolate produced the maximum IAA after 7 days of incubation on Czepak Dox Broth supplemented with tryptophan (5 mg mL-1), sucrose (30 g L-1), and NaNO3 (2.2 g L-1) at pH 6.2. Fourier Transform Infrared Spectroscopic analysis of the crude fungal extract further confirmed the production of indole-like compounds. This investigation suggested that secondary metabolites of endophytes act as a potent plant growth inducer and can be utilized in bio-based crop management techniques.