Methods to Induce Sprouting in Dormant Potato Tubers for Direct Tuber Testing of Potato Virus Y

Abstract

The ability to initiate sprouting soon after harvest to enable direct tuber testing for potato virus Y (PVY) could aid in acquiring more rapid results compared to the traditional winter grow out tests currently used. Methods to break dormancy for PVY detection using laboratory direct tuber testing by ELISA in commercially produced Ranger Russet, Clearwater Russet, and Umatilla Russet seed lots were tested over two years and compared to leaf testing results obtained from the winter grow out and spring grow out. At harvest, three 400 tuber samples from each cultivar were obtained for the trial and included (1) untreated control (UTC), (2) application of cold aerosol smoke, or (3) application of Rindite. Tuber samples were held at 18.3 C and sprout development was monitored weekly. Treatments were direct tuber tested for PVY when one treatment of that cultivar achieved three sprouts elongating to six millimeters. A fourth 400 tuber sample was collected, treated with Rindite, and included in the Idaho winter grow out plots in Waialua, Hawaii and leaves were sampled and evaluated for PVY using ELISA. Laboratory tested seed was stored and planted in a spring grow out (Kimberly, Idaho) and leaf samples were analyzed for PVY by ELISA. Rindite treated tubers had greater sprout rating and number of sprouts elongating compared to UTC tubers and tubers receiving the smoke treatment at time of PVY testing. Smoke had a greater sprout rating but did not always significantly differ in the number of sprouts elongating compared to the untreated tubers. Overall, estimates of PVY prevalence from direct tuber testing showed limited significant differences to those obtained in the winter grow out for each cultivar, year, and PVY incidence. However, in year two, the incidence of PVY in the winter grow out (7% PVY) significantly differed from direct tuber testing (16% PVY) in Ranger Russet. In both years, the spring grow out PVY results for all cultivars were not significantly different than the direct tuber testing, except in year one the Ranger Russet direct tuber tested UTC showed 10% lower PVY detection compared to the spring grow out. This study identified a novel dormancy breaking treatment to promote earlier and accurate PVY detection by direct tuber testing using ELISA and provided data to support direct tuber testing for post-harvest evaluation of PVY in seed certification.