GREENHOUSE EVALUATION OF GRAPEVINE FUNGAL ENDOPHYTES AND FUNGAL NATURAL PRODUCTS ANTAGONISTIC TO XYLELLA FASTIDIOSA FOR CONTROL OF PIERCE’S DISEASE Principal Investigators

The goal of this research was to identify fungal endophytes and fungal natural products antagonistic to Xylella fastidiosa (Xf) that could be implemented as preventative and curative treatment for Pierce’s Disease (PD) management. We showed in in vitro bioassays that several fungal endophytes isolated from grapevine wood possess anti-Xf properties, due to the production of natural products. One of those fungus (Cryptococcus) inhibited PD symptoms development and Xf titer in in planta bioassays. In addition, we purified and characterized one natural product (radicinin) produced by Cochliobolus sp. as and effective inhibitor of Xf. Radicinin has a poor solubility in water and thus was not systemic and active against Xf when injected in planta. However, in collaboration with the private sector, we successfully developed an emulsion of radicinin and treated vines inoculated with Xf. Results will be obtained later on this year. In addition, we showed that the fractions from the crude extracts of three additional fungal endophytes (i.e., Eurotium, Geomyces, and Ulocladium) also possess activity against Xf in the in vitro bioassay. Active fractions from the crude extracts of these three fungal cultures are being examined using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) to identify their chemical structures and properties. These molecules and formulation are currently under review for patentability by the Executive Licensing Officer in the UC-Riverside Office of Research and, hence, their names cannot always be disclosed in this report.