Title : Soil microbiome engineering to alleviate high salinity stress in wheat
Abstract:
1-Aminocyclopropane-1-carboxylic acid (ACC) is an ethylene precursor, whose concentration elevates in plants when they face biotic or abiotic stress. In crop production, the microbiome plays a very significant role in plant growth promotion (PGP) where some microbes in the natural soil can cleave ACC thus reducing ethylene levels in the plants and alleviating stress. The study aims to identify the role of ACC in microbiome interactions in the rhizosphere under salt stress for two different varieties of wheat i.e., Suntop, a salt tolerant cultivar and Sunmate, a salt sensitive cultivar. We hypothesize that following the approach of “targeted microbiome engineering”, recruitment of potential abiotic stress alleviating PGP rhizobacteria (PGPR) in the natural soil could be achieved by applying ACC as a soil amendment. Once ACC metabolizing bacteria have been recruited, these could then cleave ACC into ammonia and α –ketobutyrate. As a result, wheat plants grown in ACC-amended soil with high salinity would have their stress alleviated and growth promoted due to reduced ethylene levels. Qualitative screening of ACC treated soil from wheat rhizosphere was conducted to isolate and characterize the ACC deaminase-producing microbiome and its plant growth promoting activities under elevated salinity conditions. Phenotypic results showed significant growth promotion and stress alleviation potentially by the ACC-deaminase microbiome when salinity levels were elevated from 100 mM NaCl to 140 mM NaCl for the salt sensitive variety Sunmate, whereas no significant effect was shown in the salt tolerant cultivar Suntop. Microbiome analysis of rhizosphere soil samples showed a clear shift of the microbiome in the presence and absence of ACC in the rhizosphere suggesting ACC addition reconditioned the soil microbiome towards ACC metabolizing microbes. ACC deaminase bacteria overall helped plants not only in salinity stress alleviation but also provided growth promotion for wheat. Moreover, the overall performance of ACC deaminase bacteria seemed to be dependent upon the presence of salinity stress, levels of salinity and it was differential towards tolerant and susceptible wheat varieties. The long-term goal of this research is to evaluate commercial feasibility of ACC soil amendments and validate their long-term impacts on the soil microbiome and crop productivity under stress conditions.
