Abstract

Lactic Acid Bacteria (LAB) are an inhabitant of a diversified environment and plays an important role in the well-being of their habitat. These are the low-cost inputs promoting the health and wellness of humans, animals, aquacultures and crop plants and need special attention and exploration, particularly in financially crunched nations. In developing and underdeveloped countries, the cost of agricultural crop cultivation is increasing day by day, making the farmers debt-ridden to acquire the necessary inputs like crop growth-promoting nutrients and pesticides to be used in agricultural crop production. Different bio-fertilizers and bio-agents are used in the farming system but these are not a part of the human beneficial microbiome. Therefore, a low-cost input for plant growth promotion activity safe for human wellness is a need of the day in the farming system. Lactic Acid Bacteria (LAB), a known human gut microbe consumed in the form of curd, is explored as a low-cost input for plant growth promotion activity for tomato crop in the present investigation.

The LAB curd of the 7^th?-day incubation period was more effective than the curd of other incubation periods to enhance tomato seed germination (up to 100%). The per cent increase in tomato seedling’s radical length was 57.14% while plumule length was 63.63% by the 7^th? day old curd over the untreated control. The seedling root dip treatment with 7^th? days curd was more effective in increasing the plant growth parameters in tomato plants, like root and shoot biomass, and number of leaves, thereby overall increasing plant canopy/plant architecture, and yield contributing parameters like number of flowers (where the increase was in the range of 71.42 to 83.33% over untreated control), and number of tomato fruits (where the increase was double or 100% over untreated control).

Lactic acid was the main metabolic constituent of LAB growth in the curd. The concentration of lactic acid in the curd on the 7^th? day was 70.00μg/10ml curd. The commercial lactic acid concentration of 0.01M was found effective in increasing the tomato seed germination, plant height and number of leaves, thereby indicating that lactic acid was a functional metabolite playing a role in enhancing the plant growth promoting activities. LAB as a gut microbe can be used safely in the agriculture production system as a low-cost input, without threatening the environmental microbial pollution and ecological niches.

Keywords:Lactic acid bacteria; Gut microbe; plant growth promotion; Low-cost input for plant growth; Agriculture; Crop production