2018 ASHS Annual Conference

Drought stress is one of the most significant factors limiting crop quality; causing stunted growth, discolored tissue, and reduced flowering. This is particularly detrimental to floriculture crops that have a value largely dependent on aesthetics. In recent years, plant growth promoting rhizobacteria (PGPR) have emerged as a sustainable solution to alleviate abiotic stress in plants. Plant roots secrete proteins and metabolites that are utilized by PGPR, and in return, the bacteria assist in the acquisition of macro and micronutrients, production of plant growth-promoting hormones, and the reduction of stress hormones such as ethylene. Although research on PGPR has gained significant interest in recent years, much of this research has focused on agronomic crops, with little emphasis on floriculture crops. In this study, two high-throughput bioassays were developed to screen a core collection of 45 Pseudomonas strains for their potential to alleviate drought stress when applied to floriculture crop production systems. Polyethylene glycol (PEG) is a well-documented compound used in bioassays for the in vitro selection of osmotic stress tolerant bacteria. This property in bacteria is commonly correlated with the ability to alleviate drought stress in plants. A second bioassay was developed to identify bacteria that produce the enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase. Bacterial ACC deaminase reduces the amount of stress ethylene produced by plants by degrading the ethylene precursor, ACC. Of the 45 strains individually tested in the PEG and ACC-deaminase bioassays, 14 and 6 were selected, respectively. One bacteria strain was selected in both bioassays, having the potential to alleviate drought stress through two unique modes-of-action. The development of these bioassays provides a high-throughput method to select bacteria with the potential to alleviate drought stress when applied to floriculture crops. Bacteria selected in the in-lab assays will be validated in planta in greenhouse trials.