Abstract

Drought stress poses a significant challenge to sustainable agriculture, especially in regions with limited water availability. This study aimed to evaluate the effects of two native probiotic strains, Enterococcus sp. BB3 and Lactobacillus sp. BB6, on the physiological, biochemical, and yield parameters of tomato plants (Solanum lycopersicum L.) under both optimal (100% field capacity) and drought induced (60% field capacity) conditions. The research focused on the strains' potential as plant growth promoting agents and their ability to mitigate drought stress impacts. Greenhouse experiments were conducted to assess the plant growth promoting properties of the two probiotic strains, including auxin production. Key parameters measured included chlorophyll content, chlorophyll fluorescence (Fv'/Fm'), quantum efficiency (Phi PSII), and electron transport rate (ETR), as well as antioxidant activity and lipid peroxidation. Plants treated with the probiotic strains were compared against untreated controls to evaluate their effectiveness under drought conditions. The BB3 strain significantly reduced lipid peroxidation levels by 15% and increased antioxidant activity and total phenols by 20% compared to the drought stressed control, enhancing plant resilience. The BB6 strain improved photosynthetic efficiency, showing a 10% increase in quantum efficiency and electron transport rates relative to controls. Both BB3 and BB6 also promoted auxin production, stimulating root and shoot growth. Under drought conditions, BB3 treated plants showed an 18% increase in fruit weight and a 10% increase in diameter compared to controls, while BB6 improved chlorophyll a and b concentrations by 12% and 15%, respectively, under optimal irrigation. The native probiotic strains Enterococcus sp. BB3 and Lactobacillus sp. BB6 shows promise as bioinoculants for mitigating drought stress in tomato plants. Their application enhanced physiological performance, improved antioxidant and photosynthetic responses, and increased crop yield under water limited conditions. These findings support the integration of lactic acid bacteria into sustainable agricultural practices as a strategy to improve resilience and productivity in water scarce environments.