Increased Flower Production of Calibrachoa x hybrida by the Soil Fungus Mortierella elongata1

Calibrachoa (Calibrachoa x hybrida) is a highly valued solanaceous flowering ornamental plant, characterized by its drought-hardiness, abundant flowering, and diverse flower colors. Recently, the saprobic soil fungus Mortierella elongata was isolated as a root endophyte from eastern cottonwood (Populus deltoides) and identified as a potential biological amendment for bioenergy and food crops. Two greenhouse experiments were conducted by transplanting rooted cuttings of Calibrachoa cv. ‘Kabloom Deep Blue' into a potting media mixture amended with 1 or 2% volume mix ratio of millet seed colonized with one of four isolates of M. elongata. Plants were assessed weekly for flower production and 86 days post inoculation for leaf/stem, root, and total dry weight. M. elongata strain 624- significantly increased flower production compared to the non-inoculated millet seed controls at 6 and 7 wk post amendment in both experiments. Above and below ground vegetative dry weight for plants grown in potting media mixture amended with M. elongata isolates varied across isolates, fungal amendment concentrations, and experiments. Our results suggest that potting media mixture amended with M. elongata strain 624- can increase flower production of Calibrachoa during peak marketable periods. Index words: Calibrachoa, plant growth promotion, plant reproduction, biological amendment. Species used in this study: Calibrachoa (Calibrachoa x hybrida); Mortierella elongata Linnem.