Development of a liquid bioformulation using salt-tolerant plant growth-promoting Bacillus spp. from fermented panchagavya for salt stress mitigation

Abstract

Soil salinity is a major abiotic constraint limiting crop productivity, particularly in arid and semi-arid regions. Although plant growth-promoting bacteria (PGPB) are widely explored for salinity stress mitigation, the development of functionally compatible microbial consortia with stable formulations remains a key challenge. In this study, fermented panchagavya, a traditional cow-based organic formulation, was investigated as a novel microbial resource for developing a robust Bacillus-based consortium. Bacterial isolates were screened for salinity tolerance and plant growth-promoting traits, including indole-3-acetic acid, gibberellic acid, ammonia production, phosphate solubilization, and exopolysaccharide production. Based on functional complementarity and compatibility, five potent isolates Bacillus halotolerans PG-1, Bacillus rugosus PG-12, Bacillus australimaris PG-33, Bacillus aerophilus PG-35, and Bacillus safensis PG-54 were selected and identified through 16S rDNA sequencing. To enhance applicability, different liquid bioformulations were developed using thickeners and protective agents. The optimized formulation A₃ [Arabic gum (1.5%) + PEG (2.0%) + glycerol (1%)] showed maximum viability (7.94 × 10¹⁰ CFU/mL) after 120 days at room temperature. Pot experiments under 250 mmol/L NaCl stress in mungbean, mustard, sorghum, and fenugreek revealed significant improvements in plant growth. Bioformulation-treated plants showed up to 2.10-fold higher root length, 2.55-fold higher shoot length, and 3.74-fold higher dry weight compared to salt-stressed controls. These results highlight the potential of functionally compatible Bacillus bioformulation from fermented panchagavya as stable and effective bioinoculants for sustainable agriculture in salt-affected soils.

Graphical abstract

Keywords

Salinity / Fermented panchagavya / Plant growth promoting bacteria / Bacillus consortium / Bioinoculant / Sustainable organic agriculture

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Funding

Gujarat State Biotechnology Mission (GSBTM)(GSBTM/JD(R&D)/661/2022-23/00172557)

RIGHTS & PERMISSIONS

Jiangnan University