- Author: Kathy Keatley Garvey
“Most current control methods rely on chemical nematicides, but their use is increasingly limited due to environmental concerns,” wrote Siddique and colleague Clarissa Hiltl of the University of Bonn, Germany, in a newly published News and Views column, “New Allies to Fight Worms,” in the scientific journal Nature Plants.
In commenting on Washington State University (WSU) research published in the same edition, they wrote that the proposed alternative pest management strategy--naturally occurring molecules or plant elicitor peptides (Peps)—shows promise: “Engineering a naturally occurring rhizobacterium to deliver Peps to the plant root system offers a new opportunity in integrated pest management.”
It's better to build up the host plant's immune system rather than directly target the pathogen with chemical nematicides which “are highly toxic and have negative effects on the ecosystem,” declared Siddique, an assistant professor in the UC Davis Department of Entomology and Nematology.
“Plant-parasitic nematodes are among the world's most destructive plant pathogens, causing estimated annual losses of $8 billion to U.S. growers and of nearly $78 billion worldwide,” he said.
The root-knot nematode Meloidogyne chitwoodi is a noted pest of potato production in the Pacific Northwest. Idaho leads the nation in commercial potato production, followed by Washington. Oregon ranks fourth. California, which ranks eighth, grows potatoes year around due to its unique geography and climate.
In their article, Siddique and Hiltl analyzed research published by WSU Department of Pathology scientists Lei Zhang and Cynthia Gleason who demonstrated the effective use of Peps to combat root-knot nematodes in potato (Solanum tuberosum). The WSU scientists engineered a bacteria, Bacillus subtillis, to secrete the plant-defense elicitor peptide StPep1. Pre-treatment of potato roots “substantially reduced root galling, indicating that a bacterial secretion of a plant elicitor is an effective strategy for plant protection,” the Zhang-Gleason team wrote. (See article.)
Earlier scientists discovered that Peps could effectively manage nematodes in soybeans. Unlike the seed-grown soybeans, however, potatoes grow from small cubes of potatoes known as seed potatoes.
“Besides chemical nematicides, methods of nematode management include the use of crop rotation, microbial biocontrol agents, cover crops, trap crops, soil solarization, fumigation and resistant plant varieties,” wrote Siddique and Hiltl. “However, several of these strategies are not effective or available for all crops. Nematicides are highly toxic, and their use is strictly limited due to environmental concerns. Resistant plants are often ineffective or unavailable. Microbial biocontrol agents have produced inconsistent results. In this context, the current work provides a new opportunity to manage plant-parasitic nematodes by combining two progressive strategies: the use of plant elicitors to enhance crop resistance to pathogens and the use of B. subtilis to deliver.”