Desiccation-Tolerant Rhizobacteria Maintain their Plant Growth- Promoting Capability after Experiencing Extreme Water Stress

Abstract Bacteria from rhizosphere have the potential to promote the growth of plants, and could be used as inoculants to increase the crop profitability. However, under drought stress conditions, the number of bacteria associated to seeds could decrease below the minimal number of bacteria required to obtain a positive plant response. At the present work, the capability of 28 rhizospheric bacterial strains to tolerate 18 days of air desiccation stress (at 30oC and 50% of relative humidity) was evaluated. Results showed different levels of bacterial tolerance and five categories were proposed based on the bacterial survival ratio to air desiccation (BSRad): highly tolerant bacteria (BSRad˃80), tolerant (60<BSRad≤80), middle tolerant (40<BSRad≤60), low tolerant (20