Culturable endophytic bacteria of Camellia species endowed with plant growth promoting characteristics

Tea (Camellia sinensis (L.) O. Kuntze) is an economically important caffeine-containing beverage crop with massive plantation in the Northeast corner of the agroclimatic belt of India. The main aim of the work was to isolate, identify and characterize the native plant growth promoting endophytes associated with tea for future microbe based bioformulation.

A total of 129 endophytic bacteria were isolated and characterized for plant growth promoting traits such as indole-3-acetic acid (IAA), phosphate solubilization, ammonia production, biocontrol traits like siderophore and extracellular enzyme production. BOX-PCR fingerprinting was used to differentiate the various bacterial isolates obtained from six different tea species. 16S rRNA sequencing and blast analysis showed that these isolates belonged to different genera, that is, Bacillus, Brevibacterium, Paenibacillus and Lysinibacillus. Lysinibacillus sp. S24 showed the highest phosphate solubilization and IAA acid production efficiency of 268·4 ± 14·3 and 13·5 ± 0·5 µg ml^-1 , respectively. Brevibacterium sp. S91 showed the highest ammonia production of 6·2 ± 0·5 µmol ml^-1 . Chitinase, cellulase, protease and pectinase activities were shown by 4·6, 34·1, 27·13 and 13·14% of the total isolates, respectively. Similarly, 41% of the total isolates were positive for 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Further, the potent PGP isolates, S24 and S91 were able to enhance the vegetative parameters such as dry/fresh weight of root and shoot of tea plants in nursery conditions.

Our findings corroborate that tea endophytic bacteria possess the potential to demonstrate multiple PGP traits both, in vivo and in vitro and have the potential for further large-scale trials.

The exploration of tea endophytic bacterial community is suitable for the development of bioformulations for an integrated nutrient management and thus sustainable crop production and decreasing the hazardous effects of chemical fertilizers on the environment and human health.