Inoculation of halotolerant plant-growth-promoting bacteria improved the growth of chia (Salvia hispanica L.) in saline and nonsaline soils

Context Chia (Salvia hispanica L.), a nutrient-rich crop with potential application in different industries, is sensitive to salinity. Halotolerant plant-growth promoting bacteria could be a biotechnological strategy to increase chia's salinity tolerance. Aims The aim of this study was to determine the morphological and physiological response of chia plants inoculated with free-living halotolerant plant-growth promoting bacteria and grown in saline soils under greenhouse conditions. Methods A total of 15 bacterial treatments were inoculated to plants potted in soils with three electrical conductivity levels: 0.5, 4, and 6 dS m(-1). Mortality and morphological and physiological parameters were evaluated. The measured variables were used to calculate a relative growth index. Key results Bacterial inoculation had a positive effect on plants at 4 dS m(-1). Plants inoculated with Pseudomonas sp. AN23, Kushneria sp. T3.7, and C6 (Halomonas sp. 3R12 + Micrococcus luteus SA211) exhibited the best morphological and physiological performance (51% longer shoots, up to 90% heavier roots and up to 400% higher photosynthetic rate than control plants). Moreover, plants inoculated with Kushneria sp. T3.7 and C5 (Halomonas sp. 3R12 + Pseudomonas sp. AN23) showed significant increase in stomatal conductance and transpiration rate (up to 12 times) and in proline production (up to 345 mu g g(-1) leaf fresh weight) with respect to control plants (8 mu g g(-1) leaf fresh weight) under saline conditions. Conclusions The analysed extremophilic plant-growth promoting bacteria enhanced growth and stress tolerance in chia, a salt-sensitive crop. Implications Free-living plant-growth promoting bacteria isolated from hypersaline environments have potential for bioinoculant formulation for salinity-sensitive crops.