Molecular, biochemical, and comparative genome analysis of a rhizobacterial strain Klebsiella Sp. KBG6.2 imparting salt stress tolerance to Oryza sativa L.

Abstract

One-third of global agricultural land is affected by salinity, thereby limiting the, productivity and sustainability of the cropping ecosystem. Rice is a globally important, economical crop but is largely affected by soil salinity , leading to loss of standing crop. Plant growth-promoting rhizobacteria (PGPR) can be a potential solution to this problem by improving soil fertility, tolerance to stress and ultimately enhancing crop yield. However, the usage of PGPR in alleviating stress is limited and requires further investigation. In the current work, a PGPR strain, namely, Klebsiella sp. KBG6.2 was isolated from the rice rhizosphere of salt-affected agricultural fields in Odisha, India., The strain was found to be imparting salt tolerance to rice seedlings grown up to 200 mM of sodium chloride. The rice seedlings when treated with sodium chloride and coinoculated with Klebsiella sp. KBG6.2 showed better germination percentage, biomass, shoot, root length, chlorophyll content, and reducing sugar accumulation. The PGPR treatment also led to a reduction in reactive oxygen species (ROS) production, as evidenced by reduced ROS scavenging enzyme (catalase, superoxide dismutase , and peroxidase) activities and lower accumulation of the corresponding mRNA as, verified by real time PCR analysis. This was further supported by the reduced, accumulation of malondialdehyde which is an indicator of stress-induced oxidative damage. The genome sequence analysis of the Klebsiella sp. KBG6.2 strain revealed, it to contain the required genes responsible for colonization and acclimation during stress conditions. The successful root colonization was further verified by scanning electron microscopy. Further, the obtained PGPR strain could provide saline stress tolerance to rice and serve as bioinoculant for sustainable agriculture in salt-affected areas. • Isolation and characterization of a potential PGPR strain named Klebsiella sp. KBG6.2. • The PGPR strain Klebsiella sp. KBG6.2 could be used to impart saline stress tolerance to rice. • A successful strain in maintaining cellular reactive oxygen species homeostasis.