Will the beneficial properties of plant-growth promoting bacteria be affected by waterlogging predicted in the wake of climate change: A model study

Abstract

The agricultural sector today is faced with climate change that amplifies extreme climatic events. The use of plant growth promoting bacteria (PGPB) could provide a new approach to increase crop production under these new conditions. In this study, PGPB were isolated from a 5-week pot experiment conducted under greenhouse conditions using cabbage (Brassica oleracea L. var. capitata f. alba) as a model plant. Plants were exposed to either one or two long-term waterlogging events at two different stages of plant development. The results clearly showed that waterlogging leads to changes in the soil microbial community affecting both its overall structure (culturable bacterial fraction) as well as the plant growth promotion (PGP) function provided by the beneficial bacteria to the plant. In general, “the core” of the bacterial community (Bacillus, Pseudomonas, Stenotrophomonas and Peribacillus populations) remained preserved under waterlogged conditions, but shifts in their abundance were observed, with Bacillus, and Pseudomonas proliferating under these conditions. The key to adaptation to waterlogging may lie in “rare” bacterial populations isolated only under certain waterlogging conditions. In our study we identified 11 different genera that can be termed as waterlogging-tolerant. Waterlogging was also shown to induce shifts in the PGP potential, as well as on the structure of a population exhibiting a particular trait, which could eventually lead to either promotion or reduction of plant growth. While the abundances of populations promoting nutrient availability to plants were found to increase after waterlogging, biocontrol protease activity proved to be the trait most sensitive to waterlogging. Enterobacter and Pantoea species were identified as main players in biofilm formation under waterlogging conditions. Waterlogging also appears to trigger the emergence of extremophilic and acidophilic bacteria, aspect important for potential adaptation of soil bacteria to future climate projections, with Bacillus and Pseudomonas showing best potential. Based on all PGP characteristics studied, we selected 11 bacterial isolates belonging to genera Enterobacter, Bacillus, Pseudomonas, Stenotrophomonas, and Pantoea designating them as the most promising bacterial bioinoculants i.e. strains with good potential for future applications in potential waterstress recover of the soil and plants.