Amelioration of flooding stress by ACC deaminase-containingplant growth-promoting bacteria

Seeds of wild-type tomato plants Lycopersicon esculentum (Solanaceae) cv. Heinz 902 were inoculated either with Enterobacter cloacae UW4, E. cloacae CAL2, Pseudomonas putida ATCC17399/pRKACC or P. putida ATCC17399/pRK415, the first three of these bacterial strains carrying and expressing the gene for 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase. When they were 55 d old, tomato plants were flooded for nine consecutive days before a number of physiological and biochemical parameters were assessed. Characteristics that were observed include root and shoot growth, epinastic curvature in leaf petioles, ACC deaminase activity, ethylene production, and leaf chlorophyll concentration. Tomato plants that were grown from seeds bacterized with organisms expressing ACC deaminase showed a substantial tolerance to flooding stress.