Phosphate solubilizing microbes from tea garden soil exhibit cellulose degrading and caffeine utilizing potential with high plant growth promoting activity

Tea plants thrive in acidic soils that often lead to phosphorus fixation, limiting its availability for plant absorption. Moreover, cellulose and caffeine deposits impair soil fertility by immobilizing nutrients and disrupting microbial activity, reducing yields unless addressed with litter amendments. Our study evaluated five phosphate-solubilizing microbes: PSMR 6.2.9, PSMR 6.4.3, PSMR 2.1, PSMR 5.3, and PSMR 5.7, from tea gardens of the Darjeeling for cellulose degradation, caffeine utilization, and plant growth promotion. The qualitative and quantitative assays demonstrate exceptional PGP traits of isolates with PSI of 2.45 ± 0.11, IAA 64.54 ± 0.21, and ammonia production of 1.226 ± 0.05 µmol/mL. Two isolates, PSMR 5.7 and PSMR 5.3, degrade cellulose with an enzyme activity of 3 ± 0.8. Furthermore, PSMR 6.2.9, PSMR 2.1, and PSMR 5.3 showed caffeine utilization of up to 3%, suggesting their potential in nutrient recycling. The antibiosis test indicates the absence of antagonistic activity, ideal for better performance as consortia. Furthermore, a comparative analysis of individual isolates and their combination (SET I, SET II, and SET III) using pot trials reveals that plants treated with individual isolates outperform those with combined SETs, with an average increase of 87% shoot length, 50% root length, 72% fresh weight, 197% dry weight, and 76% chlorophyll content in Vigna radiata . Similarly, Cicer arietinum showed increases of 87%, 165%, 96%, 51%, and 47% in shoot length, root length, fresh weight, dry weight, and chlorophyll, respectively. These findings strongly indicate that selecting effective individual microbes enhances phosphorus bioavailability and optimizes waste recycling for superior tea productivity and long-term soil sustainability.