2017 ASHS Annual Conference

Nano-formulations that include CuO and ZnO are being considered as agricultural pesticides and fertilizers. In agricultural soils, the NPs would encounter roots that are microbially-colonized. Wheat (Triticum aestivum) seedlings, when responding to the NPs with root shortening, displayed strong microbial biofilms on the root surface upon growth from seed inoculated with a beneficial bacterium, Pseudomonas chlororaphis O6 (PcO6). Embedded particles within the biofilm showed signatures of Cu or Zn only when the NPs were present in the growth matrix and increased metal loads were measured in the shoots of these plants. Entrapment of particles within the mucilage did not eliminate systemic expression in shoots of genes related to metal chelation, transport and stress. Genes related to heightened tolerance to pathogens and protection against water stress also were expressed. Growth of the wheat seedlings with NPs did not eliminate increased drought tolerance observed in the PcO6-colonized plants. These findings indicate that the NPs were not antagonistic to the beneficial effects of root colonization by a rhizosphere microbe.