Fostering climate-resilient agriculture with ACC-deaminase producing rhizobacterial biostimulants from the cold deserts of the Indian Himalayas

Climate change is one of the most significant threats to agricultural productivity, which necessitates a need for more resilient and sustainable farming practices. Rhizobacterial biostimulants that secrete 1-aminocyclopropane1-carboxylate (ACC) deaminase and enhance crop resilience and yield can serve as a potential sustainable solution. The present study provides a comprehensive analysis of ACC-deaminase producing rhizobacteria (ACCD) isolated from cold deserts of the Indian trans-Himalayas and their efficacy to improve crop resilience and productivity under diverse climatic conditions. Thirty four efficient ACCD showed ACC deaminase activity ranging from 4.9 to 24484.3 nM alpha-ketobutyrate/h/mg/protein. These strains also exhibited broad-spectrum plant growth promotion (PGP) attributes, including tri-calcium phosphate (TCP) solubilization ranging from 2.4 to 687.5 mu g/ ml, siderophore production ranging from 62 to 224% and indole-3-acetic acid (IAA)-like auxin production ranging from 0.9 to 88.2 mu g/ml. 16S rRNA gene sequencing of efficient strains showed their belonging to 10 genera, including Acinetobacter, Agrobacterium, Arthrobacter, Cellulomonas, Enterobacter, Microbacterium, Neomicrococcus, Priestia, Pseudomonas, and Rhizobium. Among these, Pseudomonas was the dominant genus with high ACC-deaminase activity and multiple PGP traits. These strains also showed growth under various stressed culture conditions, including acidity/alkalinity, different temperatures, desiccation, and salinity. Field applications of 4 efficient and stress-tolerant ACCD, including Pseudomonas geniculata, P. migulae, Priestia aryabhattai, and Rhizobium nepotum with reduced NPK dose under two different temperate climate conditions showed a significant improvement in growth and productivity of crops such as garlic, pea, potato, and wheat in slightly acidic soils and maize in saline-sodic alkaline soils. These findings indicated the broad-spectrum potential of these efficient and stress-tolerant ACCD strains to improve plant growth and productivity across diverse soil types and climatic conditions.