D3393: Endophytic potential of Beauveria bassiana in sweet orange trees

Beauveria bassiana is an entomopathogenic fungus that is used as a biological pesticide for the control of citrus pests. The aim of this study was to assess the potential endophytism of B. bassiana in citrus via single application to the foliage. ‘Valencia’ sweet orange trees (Citrus × sinensis) grafted on ‘US-942’ (C. reticulata × C. trifoliata) were established under greenhouse conditions and assigned to a complete randomized block design replicated in two different greenhouses. The treatment groups (n = 16) were sprayed asynchronously with B. bassiana at 10⁷ spores/ml and the control groups (n = 16) with deionized water. To evaluate endophytism over time, a series of cohorts were destructively sampled and analyzed every two months. Sterile samples of plant organs (leaves, stems, roots) were placed onto potato dextrose agar (PDA) in Petri dishes amended with a selective fungicide (PDA-dodine), and bactericides to determine endophytism of B. bassiana. Plant height, stem diameter, and biomass were quantified from the cohorts to assess potential effects on plant physiology. Results of the experiment to be presented will include 1) post-spray leaves collected and pressed into PDA-dodine plates to assess colony forming units, and 2) foliage from the treatments stained with cotton blue analyzed using differential interference contrast microscopy to visualize the endophyte within the intercellular spaces of the plant.