Abstract
Endophytic entities are ubiquitous in nature with all-square bioactivity ranging from therapeutic effects toward animals to growth promoting attributes and stress tolerance activities in case of green plants. In the present study, the club moss Lycopodium clavatum for the first time has been subjected for the isolation of endophytic fungi. An exopolysaccharide (EPS) extracted from Colletotrichum alatae LCS1, an endophytic fungi isolated from L. clavatum Linn., was characterized as a β-glucan heteropolymer (composed of mannose, rhamnose, arabinose, glucose, galactose, and fucose) which plays a pivotal role in obliterating the drought stress in rice seedlings (Oryza sativa) when applied at an amount of 20, 50, and 100 ppm. The fresh weight contents of rice tissue (39%), total chlorophyll (33%), proline (41%), soluble sugar content (26%) along with antioxidant enzymes such as catalase, peroxidase, and super-oxide dismutase increased (in comparison to control of non-EPS treated seedlings) while malondialdehyde content had reduced markedly after 30 days of regular treatment. The drought resistance of rice seedling was observed at peak when applied at 50 ppm dosage. Vital parameters for EPS production like fermentation duration (5 days), medium pH (6), nutrient (carbon (glucose-7 g%/l), nitrogen (yeast extract-0.4 g%/l), and mineral (NaCl-0.10 g%/l) sources, oxygen requirements (O2 vector or liquid alkane-n-hexane, n-heptane, n-hexadecane), and headspace volume (250 ml Erlenmeyer flask- 50 ml medium, 200 ml-headspace volume) were optimized to obtain an enhanced EPS yield of 17.38 g/L-59% higher than the preoptimized one. The present study, for the first time, reported the β-glucan rich heteropolysaccharide from Colletotrichum origin which is unique in structure and potent in its function of drought stress tolerance and could enhance the sustainable yield of rice cultivation in areas facing severe drought stress.
Highlights
Endophytes are the hidden microbial entities that reside within the different parts of host tissues as a symbiotic partner of the plant taxa
Isolation of Endophyte From Tapobon Forest Patches Healthy plants of Lycopodium clavatum L. were collected from Tapobon forest of Paschim Medinipur district, West Bengal, India (Latitude 22◦25/ to 22◦57/N, longitude 87◦11/E, altitude 23 m above sea level) and endophytic fungi were isolated from stem portion of this pteridophytic plant
In total six endophytic fungi were isolated from the explants, but only one isolate was selected for this study due to its supremacy in exopolysaccharide production
Summary
Endophytes are the hidden microbial entities that reside within the different parts of host tissues as a symbiotic partner of the plant taxa. Secondary metabolites from endophytes of fungal and bacterial origin possess wide spectrum of biological activity They can act as antimicrobial agents and antioxidative therapeutics that can promote plant growth and development under abiotic stress conditions like high salinity, drought, and heavy metal toxicity (Santra and Banerjee, 2020a,b). The overexploitation of natural resources, global warming, and water scarcity is posing a serious threat to the existence of the valuable plant species on earth and affects overall agricultural production. To cope with this adverse situation, sustainable agricultural approaches are found to be the best figured solution. Polymers of biological origin can play a crucial role as they can modify the soil texture and form viscous film to retain soil moisture and can provide a positive change on the physical, bio-chemical, and genetic aspects of the plant treated with them
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