Gibberellin-producing Serratia nematodiphila PEJ1011 ameliorates low temperature stress in Capsicum annuum L.

We studied the effects of plant growth-promoting rhizobacteria (PGPR) on the physio-hormonal attributes of pepper (Capsicum annuum L.) plants grown under low-temperature stress. After initial screening for growth promoting effect on gibberellin (GA) mutant Waito-C rice seeds, the PGPRs were analysed for gibberellins (GA) production through advanced chromatographic and spectroscopic techniques. Among 17 bacterial isolates, a novel isolate PEJ1011 produced bioactive GA₄ (8.65ngml^-1) and physiologically inactive GA₂₀ (6.21ngml^-1) and GA₉ (1.64ngml^-1). The isolate PEJ1011 was identified as Serratia nematodiphila PEJ1011 using molecular techniques. To further assess it growth promoting effects, S.nematodiphila PEJ1011 was inoculated to pepper plant, where it significantly improved the growth attributes of pepper plants, while mitigated the deleterious effects of low temperature on pepper exposed to low temperature stress of 5°C. It was observed that the inoculated plants grown under normal and low temperature stress contained higher endogenous GA₄ contents. To modulate cold stress, the beneficial association of PGPR up-regulated the endogenous ABA levels in pepper plants, while reduced the endogenous jasmonic acid and salicylic acid contents. This up and down regulation of stress hormones contribute to the immediate adaptation of plants exposed to low temperature stress. Current study showed the significance of S.nematodiphila PEJ1011 association to crops grown under adverse climatic conditions, and also reports the GA producing capacity of genus Serratia for the first time.