Endophytic diazotrophic bacteria mitigate water deprivation effects in pineapple explants during acclimatization

We examined physiological and growth promotion traits in water-deprived pineapple explants inoculated with two endophytic diazotrophic bacteria. The following questions were addressed: (i) Is the root inoculation efficient to increase bacteria population associated to pineapple explants? (ii) Are nutrient concentrations improved in pineapple explants in response to endophytic bacteria inoculation? (iii) Can endophytic bacteria improve pineapple explants’ growth and photosynthesis? (iv) Is it possible to mitigate water deprivation negative effects and facilitate pineapple explants’ acclimatization using endophytic diazotrophic bacteria? Pineapple ‘Vitoria’ explants grown in vitro were inoculated with two different bacteria species. Therefore, 10 mL of bacteria suspension (108 cells mL−1) of either Burkholderia silvatlantica strain UENF 117111 or Herbaspirillum seropedicae strain HRC54 were applied in the substrate after transplantation. Uninoculated explants received 10 mL of autoclaved DYGS liquid medium (Control treatment). These treatments were subdivided in two water regimes, so that explants were either full-irrigated (FI) or non-irrigated (NI) for 24 days. Thereafter, NI explants were re-irrigated to saturation for two days. We found that: (i) The inoculation was efficient to increase bacteria associated to the plantlets; (ii) Nutrient concentrations were not improved in pineapple explants inoculated with both bacteria species; (iii) B. silvatlantica did not change both growth and photosynthetic capacity of the explants. Nonetheless, H. seropedicae inoculation caused negative effects on growth, whereas Anet was increased; (iv) The use of both bacteria delayed water deprivation effects and maintained the photosynthetic capacity through C3 metabolism intact for longer periods under water deprivation, as well as by recovering Anet after re-irrigation.