S. indica has been found to be a prime beneficial microorganism that improved the growth and development of various plant species under normal and stress conditions [3,28] (Figure 4). This endophytic fungus improved the germination rate in various plant species, such as chilli, cabbage, cucumber, eggplant, maize, okra, spinach, rice, and tobacco [11,34,35,36]. Improved seed germination under intense cold conditions in beetroot, carrot, cauliflower, onion, and radish has also been reported [17]. The application of S. indica has been reported to promote seedling growth and development by enhancing root and shoot growth, biomass, photosynthetic pigment production, and seedling vigour. [36,37,38]. Sheramati et al. [39] reported that S. indica improved the growth of Arabidopsis and tobacco seedlings by enhancing the nitrogen accumulation and expression of genes governing nitrogen reductase and the starch degrading enzyme glucan-water dikinase in their roots. These enzymes are responsible for nitrogen and starch metabolism in seedlings, which is essential for their growth and development.

This fungus is reported to promote the plant vegetative development in terms of height, leaf number, shoot and root growth, fresh weight, dry weight, as well as photosynthetic pigment and phytohormone synthesis [3,22,25,34,40,41]. Stimulation of nutrient uptake and their efficiency is also reported due to S. indica colonisation leading to improved plant growth, quality, and yield [25,42]. Improvement in other plant physiological attributes, such as inflorescence development, duration of flowering, flower size and number of flowers, have been reported with the application of the endophytic fungus S. indica [25,30,34,43]. Therefore, S. indica promotes plant growth and development by inducing earliness of host plant reproduction [44]. Furthermore, S. indica improved crop yields by elevating chlorophyll content, flower setting, grain yield, and pod number and size in crops, such as black pepper [43], fennel [45], rice [44,46], rapeseed [25], sweet potato [47], sunflower [48], and tomato [49,50].

In addition to improving the growth and production of crops, S. indica has improved the quality of the products. This impact may be attributable to increased root growth and root hair formation in plants treated with S. indica, which results in improved mineral nutrition acquisition and water uptake [9,45,51]. Singhal et al. [24] further proposed that nutrient uptake promoted by this endophytic fungus could be attributable to fungal hyphae penetrating deeper into the soil than root hair and thus absorbing more nutrients from the soil. Assimilation of macronutrients, such as nitrogen, phosphorus, potassium, sulphur, and magnesium is improved in crops, such as Poncirus trifoliata, Triticum aestivum, Brassica napus, Oryza sativa, Panicum miliaceum, Arabidopsis thaliana, etc. [7,25,46,52,53,54].

S. indica improves the availability of nitrogen by transforming the unavailable form into nitrate, which is taken up by plants [9]. Moreover, it stimulates the expression of the gene governing NADH-dependent nitrate reductase, which is responsible for nitrate assimilation in crops [9,55,56]. S. indica is able to convert organic phosphorus into plant-available form, thus improving the phosphorus uptake by plants under normal as well as under phosphorus-deficient conditions [17,57,58]. It also improves the acid phosphatase and alkaline phosphatase activities, leading to an improvement in phosphorus uptake in rice and rapeseed [58,59]. In addition to promoting soil phosphatase activities, S. indica upregulated the expression of the phosphate transporter genes (PT3, PT5, and PT6) in Poncirus trifoliata and thereby enhanced the phosphorus absorption by the plant [7]. S. indica colonisation improved the potassium concentration in tomatoes, resulting in higher levels of lycopene and ascorbic acid and therefore improving the quality of tomatoes [60]. Several studies have reported a significant increase in absorption of other macronutrients, such as calcium, magnesium, and sulphur [7,25,61,62,63]. An increase in the absorption of magnesium and sulphur is suggested due to the enhanced expression of transporters PiMgT1 and PiSulT, respectively, in plants treated with S. indica [62,63]. Moreover, the application of S. indica improved the acquisition of iron and zinc in rapeseed [25] and zinc in lettuce and Brassica napus [64,65]. Furthermore, inoculation with S. indica increased iron content in sugarcane plants by enhancing iron transportation [33,66]. Therefore, the application of S. indica has proven to enhance nutrient uptake in plants, and thus is considered as an emerging plant growth promoter. Table 1 summarises the effects of S. indica on the growth and quality of different host plants.