OSU partners on $3.2 million study to probe a costly potato pest

February 29, 2016
Nematode larva on potato root
Microscopic image of a pale cyst nematode larva on a potato root. Photo by L.M. Dandurand, U. of Idaho

CORVALLIS, Ore. – An Oregon State University researcher is part of an international team studying a tiny worm that’s causing big trouble in fields of potatoes - the fourth most consumed food staple in the world.

Dee Denver, a genomicist in OSU’s College of Science, is working with scientists from Idaho, New York, Canada, France and Scotland on a five-year, $3.2 million project funded by the U.S. Department of Agriculture. The team includes Inga Zasada, a nematode expert with the USDA’s Agricultural Research Service and a courtesy OSU faculty member.

The researchers are taking aim at potato cyst nematodes—microscopic parasites that burrow into roots of potato plants and suck out essential nutrients. While the nematodes don’t attack potato tubers, they parasitize the roots, sapping vigor and reducing yields by up to 80 percent.

A key objective of the study, said Denver, is to find less environmentally damaging strategies for controlling the pests. Currently the most effective control measure is fumigation with methyl bromide, a highly toxic, ozone-layer-depleting gas that’s increasingly being restricted because of environmental concerns.

“We’re hoping to replace fumigation with integrated pest-control strategies,” he said. “A key piece of that will be developing resistant potato varieties.”

The study focuses on two highly destructive nematode pests: the pale cyst nematode, Globodera pallida, and golden nematode, G. rostochiensis. Because infested potato fields must be quarantined, the pests greatly threaten U.S. export markets.

“The nematode problem has a global reach, in addition to posing a significant threat to Northwest and U.S. potato industries,” Zasada said.  

The U.S. crop brings farmers about $4 billion a year. Sales of potato chips, frozen potatoes and other processed potato products boost the commodity’s economic worth to more than $4 trillion, according to the researchers. Oregon farmers earned about $180 million from potatoes in 2015, according to the U.S. Department of Agriculture.

The golden nematode appeared in New York in the 1940s and so far is confined there. Some resistant potato varieties adapted to Northeastern conditions have been developed by scientists from Cornell University and state and federal agencies.

The pale cyst nematode first appeared in Idaho in 2006, possibly from contaminated seed potatoes. So far it has infested less than 1 percent of Idaho’s potato fields, but it has caused $4.4 million in direct losses, according to a 2012 economic assessment. There are no resistant russet-type potato varieties.

In their work, the researchers hope to discover:

  • Better methods for detection and diagnosis in potato fields;
  • Better understanding of how genes affect virulence;
  • Techniques to discover and engineer resistant genes into susceptible potato varieties, especially russets—the large, rough-skinned baking spuds widely grown in the Northwest; and  
  • More-precise ways to calculate risks, including the risk of economic losses from planting susceptible varieties, and the chances that a virulent nematode will escape quarantine.

Denver, Zasada and their team will also develop outreach and education programs aimed at potato growers, agricultural policymakers and the public.

For their part of the study, Zasada and Denver are looking at a third nematode type, G. ellingtonae, an apparently harmless cousin of the two harmful ones. The new type was detected in 2008 in an OSU research field near Powell Butte. Four years of strictly quarantined field trials revealed that it does not sap the vigor of potato plants or reduce yields.

“This type is worth studying because it has a similar life cycle to the destructive ones,” said Denver. “It’s a good model for understanding how the parasite does its damage, and how its genome changes as the organisms respond to environmental stresses like fumigation.”

Fumigation doesn’t always penetrate the nematodes’ tough egg sacs, or cysts, which can persist in the soil for decades even if there’s no susceptible host. The eggs, about 300 per cyst, hatch when a host - chiefly potato, but a few close relatives are also susceptible - releases triggering chemicals from its roots. The larvae burrow into the roots, feed and complete their life cycle. 

Potatoes are grown on every continent. The U.S. ranks fourth in global production, after China, the Russian Federation and India.

Author: Gail Wells
Source: Inga Zasada