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Using Natural Defense Responses to Protect Against Pest Damage in Potatoes

Posted by Georgine Yorgey | April 3, 2019

In recent months several BIOAg-funded projects came to a close. This post is a summary of one of the finished projects. To read the full project report, please follow the link within the post.

Peptide elicitors are naturally occurring signaling compounds that act within plants to induce and amplify defense responses. If specific peptide elicitors could be identified and synthesized, they could be used to maximize plants’ natural immunity, providing a more sustainable approach to controlling disease caused by pathogens and pests. Peptide elicitors do not interact directly with pests, so pests are not expected to develop resistance. As natural compounds, peptide elicitors are unlikely to have negative side effects on human or environmental health.

petri dish on left with white root hairs visible; microscopic image on right showing black dots throughout
Figure 1. A hairy root culture system and Sss infection. Left shows a hairy root culture in petri dish. Right picture shows microscopic image (200x magnification) of the root tissues infected by Sss. The picture was taken 6-8 weeks after application of purified Sss cystosori (2 x 104).

Making this potential tool a reality requires crop-specific scientific work to identify peptides that induce strong defense responses. Kiwamu Tanaka, Lee Hadwiger, and others have been laying the groundwork for the use of peptide elicitors in potato using a powdery scab disease caused by a protist pathogen, Spongospora subterranea f. sp. subterranea (Sss). Typically, powdery scab can only be studied under field conditions. Within their BIOAg project, the team developed a hairy root culture that could be used as a lab-based powdery scab infection system, and confirmed that the system can be used for rapid, scalable, high-throughput screening of peptide elicitors against powdery scab infection under controlled conditions (Figure 1).

Then Tanaka and collaborators turned their attention to identifying new peptide elicitors that evoked a stronger, and more specific response against powdery scab than STPep1, a known peptide elicitor. Multiple fractions containing active compounds were extracted and purified from infected potato cells. Each fraction was then applied to the hairy root culture system, and researchers monitored early defense response using an extracellular alkalinization assay previously developed by the team. The most active fractions contained roughly 17,000 different possible candidate peptides. Narrowing candidates to those peptides that were derived from potato and enriched in powdery scab-infected samples led to about 100 peptides that are finalist candidates. The team is proceeding to test each of these candidates for defense-inducing activity.

This BIOAg project funded one WSU Masters student, and involved two high school interns from Hunters, WA and Yakima, WA. Work completed through the BIOAg project has been leveraged to obtain additional funding from the Northwest Potato Research Consortium and USDA AFRI that will continue the work. Two scientific publications are being prepared. The full project report (PDF) is available online.

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