Evaluation of an endophytic plant growth-promoting bacterium, Klebsiella variicola, in mitigation of salt stress in tuberose (Polianthes tuberosa L.)

The information about the use of plant growth-promoting endophytic bacteria (PGPEB) with ornamental plants is still scarce. This study was designed to isolate and characterize PGPEB from different plants (Gossypium, Cyperus, Corchorus olitorius and Oryza sativa) and to evaluate their potential in plant growth promotion in tuberose (Polianthes tuberosa L.). A total of 25 isolates were obtained from the surface-disinfected plant parts. Five isolates were initially selected for their ability to produce indole-3-acetic acid and phosphate-solubilization activity in addition to the ability to form a biofilm. The most potent isolate was selected and identified as Klebsiella variicola RS-1. A pot experiment was designed to examine the ability of the selected isolate to aid tuberose withstanding different concentration of irrigation water salinity with EC values of 1.2 (control), 4.5, 6, and 7.5 ds m-1 during two successive growing seasons. At higher salinity levels (7.5 ds m-1), both inoculated and sprayed plants recorded high levels of catalase and peroxidase activities 3 and 1.5 times over untreated plants respectively. Also, leaf length was increased about 46% and 37% in inoculated and sprayed plants respectively over untreated ones. The same trend was observed in most other vegetative parameters.