Location: Temperate Tree Fruit and Vegetable Research
Project Number: 2092-21220-002-039-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jun 1, 2018
End Date: May 31, 2020
Objective:
This project uses greenhouse and field aspects to determine if tobacco rattle virus (TRV) insensitivities in potato cultivars of interest are due to environmental, nematode, or TRV isolates differences between North Dakota and Washington States.
1. Conduct greenhouse trials in North Dakota and Washington State testing for the resistance of two insensitive potato cultivars (Castle Russet and Payette Russet) and a sensitive cultivar (Russet Burbank) in side-by-side trials using stubby root nematode and TRV populations isolated from both North Dakota and Washington State soil.
2. Compare the morphology and molecular sequence of target genes of the two nematode populations used in the greenhouse experiments to identify any population differences.
Conduct field trials in Washington State testing for the resistance of two insensitive potato cultivars (Castle Russet and Payette Russet) and a sensitive cultivar (Russet Burbank), to the current North Dakota and Washington State populations of stubby root nematode and TRV.
Approach:
Controlled greenhouse trials will be conducted in both North Dakota and Washington States in order to run side-by-side experiments with the native nematode/TRV isolates from each state. Both states will ship a sample of TRV-infected nematodes collected from their local infected fields to the laboratories in the other state. This will enable two simultaneous side-by-side comparisons of the impact of different nematode populations and TRV isolates on TRV symptom development and virus detection. The nematode species from each state will be compared using molecular diagnostics of three specific genes to genotype each nematode population. Castle Russet, Payette Russet, and Russet Burbank cultivars will be planted in plastic pots containing a loamy sand. Twenty nematodes will be added at a minimum to each three week old potato plant.
One set of plants will receive North Dakota-collected stubby root nematodes, and the other set will receive Washington state-collected nematodes. At harvest, tubers will be collected from each pot, and half of the tubers will be shipped to the researchers in the other state to ensure TRV symptom scoring and the molecular detection of TRV are consistent between locations. A sample of the skin will be taken with a knife from the stem and bud ends of the tubers for nucleic acid extraction and reverse transcription polymerase chain reaction (RT-PCR) of TRV. Tubers will also be accessed for visual symptoms by generating 1-cm thick slices.
TRV incidence and symptom severity will be determined. For disease severity, a transparent grid of 1 cm squares will be placed over the tuber slices, and the number of squares with symptoms, will be counted. Data gained from the side-by-side greenhouse evaluations of the North Dakota and Washington State nematode population and TRV isolates at each location will be compared and correlated to any differences identified in nematode species or isolate, to determine if the nematode and/or virus directly causes the difference in insensitive reactions in Castle Russet and Payette Russet cultivars.
Field trials will be conducted in Washington State to assess cultivar sensitivity to TRV present. Specifically, Castle Russet, Payette Russet, and Russet Burbank cultivars will be planted in stubby root nematode and TRV-infected fields with six different replications in randomize complete block design. A research plot located at the USDA-ARS research station in Prosser will be utilized, which is managed to maintain a stubby root nematode population infected with TRV. Tubers will be harvested by replication at the end of the season. Tubers will be analyzed using the same methodology listed above in Objective 1; TRV symptom development will be scored, and RT-PCR will be performed to detect any virus in the internal tuber tissue.
If the results from Objective 1 are consistent between the nematode population and TRV isolates from North Dakota and Washington State, but the field results are different, it would indicate that the environment, and not the vector or virus is responsible for differences in TRV insensitivity in the cultivars grown in the two different states.
