Diversity of ACC Deaminase-Positive Bacteria From Winter Wheat Rhizospheres In Colorado.

Wheat is an important cereal crop whose yield must be increased in water-limited environments to meet global demand. At Colorado State University, research is underway to study factors related to drought tolerance of winter wheat, including interactions with 1-aminocyclopropane-1-carboxylate (ACC) deaminase positive bacteria. These bacteria play a key role in reducing ethylene levels in plants growing under drought stress. The purpose of this study was to assess the genetic diversity of ACC deaminase-positive bacteria associated with four winter wheat varieties (Baca, Hatcher, Ripper and RonL) grown under dryland, limited, or fully-irrigated conditions in Colorado. Rhizosphere soil was collected at two physiological growth stages to assess temporal dynamics: emergence in November and anthesis in late May. Culturable ACC deaminase-positive bacteria were isolated at anthesis and identified by 16S rRNA sequencing. Culturable species included Pseudomonas flourescens (most abundant), Pseudomonas sp., Rahnella aquatilis, and Bacillus sp. Molecular diversity was assessed by extracting DNA from rhizosphere soil, and amplifying, cloning and sequencing a portion of the acdS gene. Phylogenetic analysis of acdS amplicons will allow for a broader assessment of the genetic diversity of these bacteria, including how diversity is affected by wheat variety, physiological growth stage, and irrigation management.