Assessing the Endophytic Potential of a Commercially Available Entomopathogenic Beauveria bassiana Strain in Various Citrus Rootstocks

The citrus industry is challenged by numerous arthropods, yet extensive research has not been conducted to determine the potential use of entomopathogenic fungi as endophytes in pest management strategies. Two inoculation methods (i.e., soil drench and foliar spray) using a suspension of Beauveria bassiana (strain PPRI 5339 contained in Velifer®) containing 4 × 107 conidia mL−1 in 0.01% Tween 80 were conducted on three commercially available citrus rootstocks (i.e., ‘US-942’, ‘US-812’, ‘Swingle’). Seedlings were grown under greenhouse-controlled conditions over a 7-week observation period. Similarly, a third inoculation method (seed soaking) was conducted using seeds from the same three rootstocks. The fungus was re-isolated post-inoculation from ‘US-942’ and ‘US-812’ in the foliar spray and seed soaking treatments. In addition, the fungus was recovered from root tissue in the foliar-sprayed seedlings, suggesting possible systemic movement from leaves to roots. The fungus was not recovered from soil-drench-treated seedlings, nor from any of the ‘Swingle’ cultivars. This study assessed the potential of B. bassiana to endophytically colonize certain citrus rootstocks in planta.