Biosynthesis of auxin and other plant growth-promoting traits from novel endophyte Fusarium incarnatum SELC2 and its in vitro plant growth-promoting efficacy on rice (Oryza sativa L.).

Endophytic fungi in symbiotic relationships with their host plants are recognized for promoting plant growth and mitigating the detrimental impacts of both abiotic and biotic challenges. However, due to limited knowledge of plant growth-promoting microorganisms coupled with Pteridophytes, the objective of this investigation was to identify and characterize the fungal endophytes from Selaginella ciliaris (Retz.) Spring. The endophytic fungus Fusarium incarnatum SELC2 was isolated and identified via the 18S rDNA sequencing. The isolates exhibited phosphate solubilization, ammonia production, and extracellular enzyme production activities, and had the capacity to generate indole acetic acid (IAA) whether L-tryptophan was present or not. This research explores the optimization of a number of environmental and nutritional aspects for IAA production using Central Composite Design (CCD) with Response Surface Methodology (RSM). The ambient temperature for incubation was 34℃, pH of 6.5, incubation time of 6 days, 0.35 g/L tryptophan, and 30 g/L sucrose were identified as the ideal parameters for achieving the highest IAA production. The refined IAA was analyzed using HPTLC and HPLC, showing a pink band with an Rf value of 0.92 and a peak at 2.5 min, consistent with standard IAA. Furthermore, the impact of endophyte on the initial growth parameters of Oryza sativa L. was assessed using three rice varieties, confirming that SELC2 is a significant isolate for promoting rice vegetative growth parameters, and notable changes have been observed in the photosynthetic pigments, sugar, protein, and antioxidative enzymes across both fungal extract treatments, as well as in co-inoculation.