ISU National Seed Health System Oversees USDA Import-Testing Pilot Program

The National Seed Health System (NSHS) based at the Iowa State University (ISU) Seed Science Center (SSC) is on the front lines in the fight against a disease which effects cucurbit plants such as watermelon, squash, cucumber, pumpkin and other types of gourds.

Cucumber Green Mottle Mosaic Virus (CGMMV), first discovered in other parts of the world in 1935, showed up in the United States in a melon seed field in California in 2013.  The disease can cause serious losses, including unmarketable fruit and potentially infected seeds from infected plants.  This is damaging to both the seed industry and the fresh market.  ISU Seed Pathologist Tracy Bruns, Ph.D. is determined to stop the spread of this harmful virus. 

“This disease can be quite hard to eliminate once it is established in an area,” said Bruns. “Since the original CGMMV detection was linked to an imported seed lot, the risk of imported cucurbit seed has been at the forefront of concerns to protect the U.S. from additional introductions of the disease.” 

Bruns is part of the NSHS team operating a United States Department of Agriculture (USDA) import-testing pilot program for this disease. The National Seed Health Accreditation Pilot Program (NSHAPP) is a voluntary system of testing seed imported into the United States.  CGMMV is the first pathogen tested under the program.  Bruns says testing of imported seed lots for this virus can be an effective screening measure to mitigate the risk. 

“Roughly 25,000 imported cucurbit seed lots have been tested under this program since January of 2016,” said Bruns. “Out of those, 31 lots tested positive for CGMMV and were re-exported or destroyed to stop the seed from being planted or sold in the U.S.” 

The companies who participate in the program are large seed companies and seed brokers who are accredited by NSHS to routinely test seed for diseases.  Bruns believes additional impact would come from participation of smaller companies who may not be aware of the risk or don’t have the resources to test all of their imported material.  She is working hard to make that happen and says while the risk of seed borne diseases is always present, everyone benefits when the risk is managed through testing.  

 “The seed company will know they have done their part to protect the consumer, the production area, and themselves from the risk of outbreak,” said Bruns. 

The NSHAPP is operated with funding from the USDA Farm Bill.  Bruns’ role is to stay in touch with program participants and collate the monthly data, which she reports to the USDA.  She also works with other scientists around the world to understand the methods of testing for CGMMV that are in use elsewhere and help harmonize testing procedures.  It is a natural fit with the mission of the NSHS and the work done at the ISU Seed Lab and the SSC. 

“We have great relationships with many people and companies within the seed industry,” said Bruns.  “Working with them on these issues to take a proactive approach is a win for everyone.”

For more information on CGMMV and NSHAPP visit