Location: Emerging Pests and Pathogens Research
Project Number: 8062-22000-022-008-I
Project Type: Interagency Reimbursable Agreement
Start Date: Aug 15, 2015
End Date: Aug 14, 2020
Objective:
The primary goal of this research is to screen a collection of wild potato relatives to discover new germplasm that confer resistance against different PCN species. The identification of the resistant sources may allow quick transfer of resistance genes to current potato cultivars, thereby providing effective alternatives for the control and eradication of PCN in the U.S. The objectives of this project includes 1) Evaluation of the expression of candidate effector genes in the three Globodera nematode species, 2) Using conserved effectors to screen wild potato accessions for a hypersensitive response, and 3) Confirmation of the identified wild potato accessions for resistance to the three Globodera nematode species.
Approach:
Evaluation of the expression of candidate effector genes in the three Globodera nematode species. Nematodes secrete a variety of effectors. We will target effector genes that show dramatic upregulation during the early stages of nematode parasitism. The expression of candidate effector genes will be evaluated in G. rostochiensis, G. ellingtonae and G. palllida using RT-PCR or RT-qPCR. Effector genes that are confirmed to be expressed in the three species will be further cloned and compared to identify effector genes that are conserved among the three Globodera species. These conserved effector genes likely play essential roles in nematode parasitism.
Using conserved effectors to screen wild potato accessions for a hypersensitive response. The production of a localized hypersensitive response (HR) is often occurred following nematode infection in a resistant plant. An agroinfiltration assay in potato leaves has been developed that provides a quick observation of the HR phenotype when a nematode effector is recognized by a matching R protein in the plant. The agroinfiltration assay allows a high-throughput testing of large plant collections. We will use this agroinfiltration system to express each of the conserved effectors in the leaves of wild potato plants and screen for an HR phenotype on the infiltrated leaves. Plants showing an HR phenotype may contain R genes that confer broad-spectrum resistance to the three Globdoera nematode species.
Confirmation of the identified wild potato accessions for resistance to the three Globodera nematode species. Wild potato accessions showing an HR phenotype in the infiltrated leaves will be further evaluated for nematode resistance, which will be conducted in the labs of Drs. Wang (ARS, Ithaca, NY), Dandurand (U. of Idaho), and Zasada (ARS, Corvallis, Oregon) for G. rostochiensis, G. pallida, and G. ellingtonae, respectively, using established protocols. Tested wild accessions will be grown in pots and inoculated with 2,000 nematode eggs when they reach 10 centimeter in height. Susceptible potato varieties, such as Desiree and Russet Burbank, will also be included as controls. Plants will be harvested approximately 90 days after nematode infection and nematode cysts will be extracted from air-dried soil. A final nematode egg count will be obtained to determine if the identified wild potato plants confer broad-spectrum resistance to multiple Globodera nematode species.
