1a. Objectives (from AD-416):
Conduct bioassays to evaluate the resistance of existing clones/cultivars in the potato breeding program to the Globodera pallida population originating from the Shelley, Idaho area.
1b. Approach (from AD-416):
The European Union protocol for resistance testing (The Council of the European Union, 2007) will be used to screen existing potato clones/cultivars for resistance. Experiments shall be performed in pots with soil temperatures during the experiment not exceeding 25ºC. The potato varieties ‘Desiree’ (internationally relevant) and ‘Russet Burbank’ (regionally relevant) will be used as standard susceptible control varieties in each test. Sante will be used as a standard resistant variety. In addition, differential potato clones from Scotland with resistance genes for G. pallida and/or G. rostochiensis will be included in the screening to allow genotyping of the resistance found. The Globodera inoculum (Pi) will consist of approximately 5 viable eggs or juveniles per ml of soil. Cysts used in experiments will be kept for at least four months at 4ºC, and have a viability of at least 70% as determined by Meldola Blue staining (Kroese et al., accepted). At planting, one sprouted potato eye plug will be planted into infested soil. There will be at least six replicates of each tested potato variety and the standard susceptible control varieties will be replicated 10 times. The duration of the experiment will be at least twelve weeks. At the end of the experiment, Globodera cysts will be extracted from soil using a Fenwick cyst extractor and the final population (Pf) determined by crushing cysts and counting eggs and juveniles. A multiplication rate of at least 20 (Pf/Pi) on the standard susceptible control variety shall be achieved for the test to be considered valid. The relative susceptibility of the tested potato clones/cultivars to the standard susceptible control variety will be determined as: Relative susceptibility (RS) = Pftest variety/Pfstandard susceptible control variety x 100% A set of approximately 23 breeding clones and cultivars will be screened for PCN resistance. All clones will be provided by the Aberdeen Breeding Program.
3. Progress Report:
Progress in this project is related to Objective 1 in the parent project which emphasizes developing enhanced potato Germplasm and varieties for market classes in the western U.S. with a focus on recurrent and emerging diseases, such as cyst nematodes. The summary of work outlined below involves bioassays of breeding material from the parent project for pale cyst nematode resistance. Twenty-six potato lines in tissue culture tubes were received at the University of Idaho from the Agricultural Research Service-Aberdeen, Idaho. A few tubes were contaminated and discarded, the remaining lines have been propagated once, with each line generating between 4 and 12 plantlets each. A second round of propagation is planned. Potato lines at the University of Idaho, including five potato cyst nematode differential lines and susceptible cultivars are also being propagated in tissue culture. Supplies related to the European Union protocol for resistance testing have been ordered in anticipation of inoculation later this year. Globodera pallida cysts (Idaho population) have been reared on susceptible potato lines at the University of Idaho secure greenhouse facility. Cysts to be used in resistance experiments are being stored at 40°F and will be tested for viability at the time of inoculation.