Effects of rhizobacteria producing deaminase enzymes for aminocyclopropane-1-carboxylate on drought tolerance and post-stress recovery in creeping bentgrass under field conditions

Some endophytic rhizobacteria, including species producing deaminase enzymes for 1-aminocyclopropane-1-carboxylic acid (ACC) suppressing ethylene production (ACCd), form symbiosis with plant roots to enhance plant growth and stress tolerance. The objectives of this study were to determine growth-promoting effects and effective rates of inoculation with ACCd-producing Paraburkholderia aspalathi (WSF23 and WSF14) on creeping bentgrass (Agrostis stolonifera L.) performance under deficit irrigation in field conditions and effectiveness on post-stress recovery during re-watering. Turf field plots established with ‘L-93’ creeping bentgrass were inoculated with P. aspalathi strains (WSF23 and WSF14) through soil drenching either as a single strain or as a combination of both strains. After inoculation, plots were subjected to drought stress with deficit irrigation to replace 60% of the daily evapotranspiration rate, followed by re-watering for post-stress recovery. Three inoculant rates of 1.0, 1.5, and 2.0 × 10⁷ colony-forming units (CFUs) were evaluated to determine the most effective dosage to apply under field conditions. Inoculation of plants with the consortium of the two strains at 1.5 × 10⁷ CFUs was most effective in enhancing turf quality, percent green cover, normalized difference vegetation index, and dark green color index during drought stress and recovery periods. These results suggest that creeping bentgrass tolerance to drought stress and improved post-stress recovery could benefit from inoculation with P. aspalathi strains under field conditions and also ACC deaminase-producing rhizobacteria could be incorporated into turf management programs to maintain creeping bentgrass during abiotic stress conditions.