Diversity and Abundance 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+ bacteria associated with four winter wheat varieties (Baca, Hatcher, Ripper and RonL) grown under dryland or fully-irrigated conditions in Colorado. The abundance of ACC+ bacteria was relatively high, with numbers ranging between 1.69 × 10⁷- 3.28 × 10⁹ CFU’s g^-1. At wheat flowering stage, the abundance and relative percent of ACC+ was greater under dryland and limited irrigation than full irrigation, and greater under RonL than other varieties. ACC+ bacteria from each variety x irrigation treatment soil were enriched in selective media with ACC as the sole C and N source. Bacterial cells were pelleted and DNA was extracted and the 16SrRNA genes were amplified and pyrosequenced to generate ACC+ bacterial libraries for abundance and diversity assessments.  Results will provide evidence of whether ACC+ bacterial composition and diversity are affected by wheat variety and irrigation management.