Location: Emerging Pests and Pathogens Research
Project Number: 8062-22000-022-000-D
Project Type: In-House Appropriated
Start Date: Feb 26, 2017
End Date: Feb 25, 2022
Objective:
Our long-term objective is to develop improved management strategies for the range of pathotypes of the major invasive and emerging nematode and virus pathogens affecting the United States potato crop. While the potato industry is eager to improve cultural and genetic (i.e. resistance) management strategies that can be readily translated to the field, they are also interested in developing fundamental information on emerging pathogens to ensure appropriate and timely detection and the development of novel management strategies. Over the next 5 years we will focus on the following:
Objective 1: Define the genetic diversity and evolution of PCN and virus populations, and optimize associated diagnostic assays. [NP303, C1, PS1]
Sub-Objective 1.1: Compare genome sequences of G. rostochiensis pathotypes (Ro1 and Ro2) to identify sequence variations that may be used for developing molecular diagnostic markers.
Sub-Objective 1.2: Monitor PVY strain diversity in the seed potato crop.
Sub-Objective 1.3: Characterize PVY diversity and evolution.
Objective 2: Discover and characterize genes and proteins regulating virus-vector-host and nematode-host interactions. [NP303, C2, PS2A and PS2C]
Sub-Objective 2.1: Characterize candidate effector protein-encoding genes and their associated host proteins contributing to nematode parasitism and virulence.
Sub-Objective 2.2: Characterize infection and transmission competence of PVY strains and strain combinations in potato and aphid populations.
Sub-Objective 2.3: Define the mechanism of tissue tropism of poleroviruses in plants and aphid vectors.
Objective 3: Develop virus and nematode resistant potatoes that are acceptable to the potato industry and consumers. [NP303, C3, PS3A]
Sub-Objective 3.1: Determine the resistance of potato clones and wild potato species to G. rostochiensis pathotypes.
Sub-Objective 3.2: Collaborate with potato breeders to develop genetic markers for phenotypic traits useful in the development of durable virus resistance.
Approach:
In general, nematode parasites and virus diseases of potatoes cause severe crop loss and effective control measures are lacking. Nematicides effective against the Potato cyst nematodes (PCN) are no longer available and alternative control strategies for emerging pathotypes/populations have not been developed. Similarly, virus disease control strategies are completely lacking. New plant biotechnologies will provide the basis for the development of novel methods of nematode and virus control, but the success of these methods will be dependent upon a more complete understanding of the fundamental mechanisms of host-nematode and host-virus-vector interactions. One approach is to define the genetic diversity and evolution of PCN and virus populations, and optimize associated diagnostic assays. Inbreed lines of different races of PCN will be sequenced. Candidate SNPs and other variations indicated to be unique for PCN pathotypes will be further analyzed and converted into PCR-based or other types of markers and finally validated by examining a range of PCN populations. Virus populations and strains will be monitored in the potato crop to identify new recombinants and facilitate diagnostic updates. Effects of vertical and horizontal transmission on virus populations will provide information on selection pressures most important in driving the emergence of new strains. A second approach is to discover and characterize genes and proteins regulating virus-vector-host and nematode-host interactions. Stylet-secreted PCN effector proteins that manipulate multiple host cellular processes to promote successful infection will be discovered and characterized by multiple technologies to better understand the function of these effectors in nematode parasitism and virulence. Virus work with focus on the infection and transmission competence of Potato virus Y (PVY) strains to identify factors that regulate virus acquisition and transmission by aphids and synergistic/antagonistic interactions of PVY strains in plants that limit the availability of virus to aphid vectors. We will continue to investigate how potato leafroll virus protein domains direct long distance virion movement while other domains direct virus cell to cell movement of RNA-protein complexes. The third approach is to develop virus and nematode resistant potatoes that are acceptable to the potato industry and consumers. Working with breeders we will continue to use bioassays and marker assisted selection to evaluate breeding clones and wild potato accessions for nematode resistance and develop genetic markers linked to phenotypic traits caused by PVY infection such as tuber necrosis and leaf necrosis. Conceptually novel information on the population genetics of nematode, aphid and virus pests of potato crops, and on host–pathogen-vector interactions will aid in the development of new effective biologically-based disease control strategies. Improved virus and nematode diagnostics as well as genetic markers for disease resistance and disease resistant cultivars developed through conventional breeding and genetic engineering can be transferred readily to customers.
