Transmission of Potato Purple Top Phytoplasma to Potato Tubers and Daughter Plants

Abstract

In 2006, 2007, and 2008, Alturas, Russet Burbank, FL1867, FL1879, Russet Norkotah, Ranger Russet, Shepody, and Umatilla Russet potatoes were planted at a research farm near Moxee, WA. Plants were allowed to become infested with native populations of the beet leafhopper which are known vectors of the Columbia Basin potato purple top phytoplasma, a member of phytoplasma group 16SrVI, in this region. Symptomatic plants were tested by PCR for the presence of the phytoplasma and positive plants were identified with flags. Tubers were harvested from positive plants and tested for the presence of phytoplasma. A subset of phytoplasma-positive tubers was planted in a greenhouse and the resulting daughter plants were tested for phytoplasma. The frequency of tuber transmission ranged from 4% to 96% among the eight cultivars over the 3 year period. Transmission of the phytoplasma from infected tubers to daughter plants ranged from 0% to 50% depending upon cultivar and year. In two of the 3 years, Russet Burbank showed the lowest rate of tuber transmission among the eight cultivars. Across the eight cultivars an average of 22%, 15%, and 16% of infected tubers gave rise to infected daughter plants in 2006, 2007, and 2008, respectively.