Ocimum sanctum grown as rain-fed crop, is known to be poorly adapted to waterlogged conditions. Many
a times the crop suffers extreme damages because of anoxia and excessive ethylene generation due to
waterlogging conditions present under heavy rain. The usefulness of 1-aminocyclopropane-1-carboxylic
acid (ACC) deaminase-containing plant growth promoting rhizobacteria was investigated under waterlogging
stress. The comparison of herb yield and stress induced biochemical changes of waterlogged and
non-waterlogged plants with and without ACC deaminase-containing microbiological treatments were
monitored in this study. Ten plant growth promoting rhizobacteria strains containing ACC-deaminase
were isolated and characterized. Four selected isolates Fd2 (Achromobacter xylosoxidans), Bac5 (Serratia
ureilytica), Oci9 (Herbaspirillum seropedicae) and Oci13 (Ochrobactrum rhizosphaerae) had the potential to
protect Ocimum plants from flood induced damage under waterlogged glass house conditions. Pot
experiments were conducted to evaluate the potential of these ACC deaminase-containing selected
strains for reducing the yield losses caused by waterlogging conditions. Bacterial treatments protected
plants from waterlogging induced detrimental changes like stress ethylene production, reduced chlorophyll
concentration, higher lipid peroxidation, proline concentration and reduced foliar nutrient
uptake. Fd2 (A. xylosoxidans) induced maximum waterlogging tolerance as treated waterlogged plants
recorded maximum growth and herb yield (46.5% higher than uninoculated waterlogged plants) with
minimum stress ethylene levels (53% lower ACC concentration as compared to waterlogged plants
without bacterial inoculation) whereas under normal non-waterlogged conditions O. rhizosphaerae was
most effective in plant growth promotion.