Hop Stunt Viroid: Effects on Vegetative Growth and Yield of Hop Cultivars, and Its Distribution in Central Washington State.

Hop stunt viroid (HSVd) is an economically important pathogen that reduces growth and yield of hops. Visual symptoms of infected hop are highly dependent on cultivar. A study was conducted using six cultivars of hop to determine the impact on yield.

Population Biology of Pseudoperonospora humuli in Oregon and Washington.

Pseudoperonospora humuli populations from Oregon and Washington were analyzed for genetic variation using random amplified polymorphic DNA (RAPD) and DNA amplification fingerprinting (DAF) markers. The genetic structure of the Oregon and Washington populations differed considerably. There was little genetic diversity in Washington, with only five RAPD and six DAF groups detected among 40 isolates tested.

Incidence and Spatial Distribution of Viruses in Hop Gardens of Washington State.

The incidences of Hop latent virus (HpLV), Hop mosaic virus (HpMV), and American hop latent virus (AHLV), members of the genus Carlavirus, and Prunus necrotic ringspot virus and Apple mosaic virus, members of the genus Ilarvirus, were assessed for two hop cultivars, Horizon and Nugget, in Washington State. The spatial distribution of plants infected by the carlaviruses was assessed in two Horizon gardens in 2000 and one Nugget garden in 1993, 1994, and 1995. In the first Horizon garden (garden 1) and the Nugget garden, plants were separated by 2.