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United States Department of Agriculture

Agricultural Research Service

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Research Project: Rapid and Reliable Diagnostics to Identify the Tuber Necrotic Isolates of Potato Virus Y

Location: Biological Integrated Pest Management Unit

Project Number: 1907-22000-021-21
Project Type: Specific Cooperative Agreement

Start Date: Jul 01, 2013
End Date: Jun 30, 2016

Objective:
Develop a diagnostic tool that can rapidly and reliably identify PVY infections that can result in tuber necrosis disease in susceptible potato cultivars so that those affected lots can be removed from the Certified Seed system.

Approach:
PVYNTN isolates induce tuber necrosis and a foliar hypersensitive response in cultivars expressing the Nz gene. PVY isolates known to not induce tuber necrosis also did not induce a foliar HR in Nz expressing cultivars. Furthermore, the expression of foliar and tuber symptoms in the Nz expressing cultivar were enhanced when the plants were maintained at elevated temperatures. We hypothesize that we can use the Nz gene to rapidly identify tuber necrotic isolates of PVY of any of the strain groups, i.e. PVY isolates that induce a foliar HR in Nz expressing cultivars are likely to induce tuber necrosis. Using sequence comparisons for over a hundred PVY isolates that differ in their ability to cause foliar and tuber necrosis we can determine shared regions of genomes that are correlated with various phenotypes and may represent genetic determinants for foliar and/or tuber necrosis or that may be useful as biomarkers for those phenotypes. We can further test these linkages using an infectious clone of PVY that has recently been made available along with standard molecular biology and reverse genetic techniques to pinpoint the sequences in the PVY genome responsible for foliar HR and tuber necrosis. To identify any general temperature effects on PVY infection that contribute to the expression of tuber necrotic disease plants will be inoculated with PVY isolates that differ in their ability to cause HR and tuber necrosis and maintained at four different temperature regimes that mimic average min-max daily temperature, day length, and humidity fluctuations in various potato growing regions. Foliar and tuber symptoms will be assessed and the data used to build a predictive model of how the Nz gene can be expected to influence foliar and tuber necrosis symptoms in different environments. Development of new diagnostics to rapidly identify tuber necrotic isolates could be as simple as developing protocols for the mechanical inoculation of Nz expressing potato cultivars and the observation of a hypersensitive response on the foliage. This could be a simple, quick and reliable assay immediately available to any seed certification program or any grower. Enhanced serological or nucleic acid based (e.g. PCR) assays would be developed based on the data from the reverse genetic experiments that will identify virus genome sequences that are directly or indirectly linked to expression of tuber necrosis under some defined temperature regime.

Last Modified: 9/2/2014
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