Improved heat stress tolerance of wheat seedlings by bacterial seed treatment

To investigate if rhizosphere bacteria can improve heat tolerance of wheat. Wheat (Triticum aestivum) seeds of the cultivars Olivin and Sids1 were treated with Bacillus amyloliquefaciens UCMB5113 or Azospirillum brasilense NO40 and young seedlings tested for management of short term heat stress. Bacterial treatment improved heat stress management of wheat. Olivin showed higher heat tolerance than Sids1 both with non-inoculated and inoculated seeds. Heat increased transcript levels of several stress related genes in the leaves, while expression was lower in inoculated plants but elevated compared with the control. Enzymes of the ascorbate-glutathione redox cycle were activated in leaves after heat challenge but showed a lower response in inoculated plants. Metabolite profiling distinguished different treatments dependent on analysis technique with respect to primary and secondary metabolites. Analysis of some plant stress regulatory genes showed that bacterial treatment increased transcript levels while effects of heat treatment varied. The improvement of heat tolerance by bacteria seems associated with reduced generation of reactive oxygen species (and consequently less cell damage), small changes in the metabolome while preactivation of certain heat shock transcription factors seems important. Seed inoculation with beneficial bacteria seems a promising strategy to improve heat tolerance of wheat.