Biostimulant effect of green soil microalgae Chlorella vulgaris suspensions on germination and growth of wheat (Triticum aestivum var. Achtar) and soil fertility

Microalgae-derived biostimulants are increasingly used as viable tools to improve growth, yield of crops, and reduce agricultural environmental footprint. However, microalgae isolated from aquatic environments are the main strains used in the production of biostimulants. This study aims to evaluate the biostimulant effect of a terrestrial Chlorella vulgaris strain isolated from arid soil on germination and growth of wheat (Triticum aestivum, var. Achtar). Different concentrations 0.2 %, 0.5 %, 25 % and 50 % (v/v) of four C. vulgaris treatments (aqueous extract, filtered culture, crude culture and sonified culture) were investigated by measuring several biometric parameters to assess wheat germination and growth performance. All C. vulgaris treatments significantly enhanced wheat germination and growth with concentration dependent effect. The crude culture and filtrate at 25 % were the most effective compared to untreated plants. They significantly improved wheat germination index by 16.86 %, germination rate coefficient by 7.87 %, germination energy by 20.40 % as well as growth parameters such as root length (62.82 % and 52.84 %), stem length (71.36 % and 59.19 %), and root (662.5 % and 391.67 %) and stem dry biomass (675 % and 370.83 %), respectively. Principal Component Analysis (PCA) revealed that crude culture and filtrate at the lowest doses of 0.5 and 25 % were closely correlated to enhanced wheat root and shoot length and dry weight. The plant nutrients, mineral elements, chlorophyll a, total proteins and carbohydrates contents were positively correlated with enhanced shoot length and dry weight. The soil physicochemical properties were significantly increased under all C. vulgaris treatments at higher dose (50 %) whereas plants N and P contents enhancement was correlated to the soil nutrients increase. Thus, the results highlighted the potential of soil microalgae as an eco-friendly biostimulant for promoting sustainable agriculture.