Rhizosphere Engineering to Promote Drought Tolerance in Winter Wheat.

Plants cope with drought and other abiotic stresses by a variety of mechanisms that occur above- and below-ground. Below the soil surface, root length, density, and architecture may contribute to differences in drought tolerance. Recent studies have also revealed complex interactions with root-associated microbial communities that are correlated with tolerance to moisture stress. An important group of soil bacteria involved in plant abiotic stress tolerance is ACC deaminase positive (ACC+) bacteria. These bacteria degrade the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) via action of their ACC deaminase enzyme, which results in greater root elongation and tolerance to water stress. Previously, we discovered that winter wheat cultivars differ in root length and distribution, as well their root exudate chemical profiles and ability to establish large populations of ACC+ bacteria in the rhizosphere. Bacterial species composition also differs among wheat cultivars. In this presentation, we describe greenhouse and field studies that investigate both root traits and root-microbial interactions of winter wheat cultivars that range from drought susceptible to drought tolerant. We hypothesize that drought tolerance of winter wheat can be improved when wheat roots establish interactions with specific ACC+ bacteria, leading to an enhanced root architecture that more effectively taps soil moisture. Ultimately we aim to “engineer” rhizospheres by selecting wheat genotypes with specific root exudate profiles that promote the growth and activity of ACC+ bacteria, so that wheat productivity is enhanced in drought-prone, semi-arid soils.