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POSTERS: Pathogenicity and host specificity

Cross infectivity of powdery mildew isolates originating from hop (Humulus lupulus) and industrial hemp (Cannabis sativa) in New York
Bill Weldon - Cornell University. Christine Smart- Plant Pathology and Plant-Microbe Biology Section, Cornell Agrtech, Lawrence Smart- Horticulture Section, Cornell Agritech, Maire Ullrich- Cornell University, David Gadoury- Cornell University

Production regions of hop (Humulus lupulus) and industrial hemp (Cannabis sativa) significantly overlap in North America. Demand for hops are driven by craft brewers seeking locally-sourced ingredients. The 2014 Farm Bill created hemp pilot programs for fiber, seed, and cannabidiol production. Both are hosts of powdery mildew pathogens, but prior reports do not indicate cross infectivity of the pathogen species most commonly reported on each host: Podosphaera macularis for hop, and Golovinomyces spadiceus for hemp. We transferred two isolates of powdery mildew pathogen originating on hop to hemp, and two isolates from hemp to hop. The hemp isolates were derived from two NY greenhouse hemp operations. Based on morphology and sequencing of 28S and ITS regions, both matched reports classifying the pathogen as G. spadiceus. The two hop isolates were obtained from feral hops in NY and were similarly confirmed as P. macularis. The highly mildew-susceptible hop variety ‘Symphony’ was sparsely colonized by G. spadiceus, which produced hemp-infective conidia on hop, albeit at a lower density than on hemp. P. macularis did not grow on the CBD hemp variety ‘TJ’s CBD’, inducing a non-host incompatibility response. However, on the dual-purpose hemp variety ‘Anka’, P. macularis isolates representing both MAT1-1 and MAT1-2 mating types grew rapidly and sporulated profusely. The foregoing cross infectivity may significantly affect disease risks and regulatory concerns as production regions continue to expand.