IAA and ACC deaminase producing-bacteria isolated from the rhizosphere of pineapple plants grown under different abiotic and biotic stresses

The roles of plant growth-promoting rhizobacteria in promoting plant growth and soil health, including alteration in plant metabolism and production of phytohormones such as indole-3acetic acid (IAA) and the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, are indisputable. This study aimed to isolate and characterize beneficial bacteria isolated from the rhizosphere of pineapple from distinct stress-inducing habitats, including water excess-, herbicide-over-treated-, and pathogen-infected areas at PT Great Giant Foods located in Lampung, Indonesia. The isolated bacteria were screened based on IAA production and ACC deaminase activities. Six selected isolates produced IAA with concentrations of up to 36.93 mgL-1. The highest value belongs to Bacillus sp. NCTB5I, followed by Brevundimonas sp. CHTB 2C (13.13 mgL-1) and Pseudomonas sp. CHTB 5B (6.65 mgL-1). All isolates were detected with ACC deaminase activities with Brevundimonas sp. CHTJ 5H consuming 88% of ACC over 24 h, the highest among all. Brevundimonas sp. CHTB 2C was detected with the highest ACC deaminase activity with the value of 13,370 nm & alpha;-ketobutyrate mg- 1h- 1. In another experiment, it was revealed that all selected isolates promote soybean growth. These bacteria are potential to be developed in the future as bioagents to promote plant growth, especially under stressful environmental conditions.