Project Number: 1907-22000-018-00
Project Type: Appropriated

Start Date: Feb 26, 2007
End Date: Feb 25, 2012

Objective:
The long-term objective of this project is to develop an improved understanding of how endemic and emerging pathotypes of nematodes and viruses become established and are subsequently maintained in potato and grain crops. This knowledge is critical to the development of effective and sustainable control strategies, and obtaining this knowledge has become more imperative due to recent events. The emergence of new pathotypes of the golden potato cyst nematode (GN, Globodera rostochiensis), has raised new concerns about the ability of scientists and regulatory agencies to detect the nematode and about the continued effectiveness of current quarantine and management strategies. Similarly, national surveys of Potato virus Y (PVY) in seed potato production areas indicate an increase in the genetic diversity of PVY and emergence of necrotic forms of the virus. All of these findings are restricting interstate and international movement of potatoes. Over the next 5 years we will focus on the following objectives: Objective 1: Improved detection and characterization of emerging pathotypes of the GN and emerging strains of PVY. Sub-objective 1.A. Develop molecular markers that differentiate pathotypes of the GN based on divergence in nematode parasitism gene sequences. Sub-objective 1.B. Determine the geographic and genetic distribution of PVY strains affecting the U.S. potato crop and develop improved diagnostic assays. Objective 2: Identification and characterization of genes regulating the pathogenicity and transmission of viruses and nematodes affecting potato, and viruses affecting small grains. Sub-objective 2.A. Identify and characterize nematode parasitism genes. Sub-objective 2.B. Identify and characterize aphid and virus genes regulating virus transmission. Objective 3: Development of industry and consumer acceptable potato genotypes that express novel or improved resistance to virus and nematode pathogens.

Approach:
Genetic diversity and diagnostic studies will identify differences in nematode parasitism genes that may be involved in pathogenicity or virulence/avirulence of the nematode. This information will be used to develop molecular diagnostic tools that will distinguish these two pathotypes. Serological, biological, and molecular characteristics of PVY isolates representative of each state, potato variety and production area will be used to group virus isolates and develop improved diagnostic assays to detect the strains of the virus that are potentially the most economically damaging in terms of yield and trade. Functional studies of pathogenicity and transmission genes will focus on secretory proteins encoded by parasitism genes expressed within the nematode¿s esophageal gland cells known to be the principal molecular signals regulating both pathogenicity and virulence/avirulence of the nematode; as well as on aphid genes expressed in gut and salivary tissues whose products interact with specific domains on the two virus structural proteins. Genomic and proteomic based technologies will be employed to identify and characterize nematode and aphid proteins, and determine their functional role in the host-parasite/pathogen interaction. The development of nematode resistant potato varieties will focus on conventional breeding practices to transfer known nematode resistance genes to new germplasm with improved horticultural traits. Transgenic technologies will be used to isolate potato genes required by viral pathogens for replication, modify these potato genes and re-introduce them into accepted potato varieties so the altered forms no longer support virus replication.