New Lso bacterium haplotypes found in Oregon potato crops

USA – Researchers from the Agricultural Research Service (ARS), have identified three new variations of the bacterium responsible for the destructive “zebra chip” disease, threatening potato crops in Oregon’s Klamath Basin.

These findings could lead to changes in pest management strategies, but many questions remain unanswered.

Scientists previously knew about two types of Candidatus Liberibacter solanacearum (Lso) bacterium, which causes zebra chip disease, but recent research has uncovered three new variations.

Alongside these findings, four new psyllid species capable of carrying the bacterium were also identified.

“The discovery of new Lso haplotypes in non-potato psyllid species suggests that our understanding of the Liberibacter pathogen biology is still limited,” said Kylie Swisher Grimm, a plant pathologist at the ARS.

These new psyllid species, belonging to different families, may have a broader plant host range than previously thought.

Zebra chip, first detected in the U.S. in Texas in 2000, causes unsightly striping inside the potato, rendering it unmarketable. While not harmful to humans, the disease leads to massive economic losses for farmers.

“A recent review pegged economic losses to zebra chip disease in the U.S. and Mexico in the tens of millions of dollars,” noted Dr. Horton from the ARS.

The biggest concern now is whether these new bacterium variants can infect potatoes in the same way as the original Lso haplotypes.

Swisher Grimm explained, “Scientists are now facing several questions: Can these psyllids transmit the new Lso haplotypes to potatoes? Can they cause the same yield and quality losses as the current haplotypes?”

Unfortunately, once the bacterium is inside a potato plant, there’s no treatment to stop the disease. “There are no ‘rescue’ treatments for crop plants that have become infected by Lso,” Horton added.

Controlling the disease, therefore, depends on controlling the psyllid population, often through insecticide use.

Next steps in the research

Ongoing research is focusing on better understanding the biology of both the psyllid species and the Lso bacterium.

“We targeted specific genes within the Lso pathogen and psyllids to generate sequence data that could help us better identify and characterize our specimens,” Swisher Grimm explained.

With the stakes so high for potato growers, more research is critical. “This information provides a good starting point for researchers working to understand the range of a new pathogen haplotype or insect vector,” Scott Elliott, an ARS researcher, concluded.

Meanwhile, research on other potato diseases continues. Dr. Dawn Bignell from Memorial University recently received a USD 240,000 grant to study common scab, another potato disease caused by harmful bacteria.

Bignell emphasized the importance of this research, stating, “Though the potatoes are safe to eat, the lesions significantly reduce their quality and market value, which can be devastating for farmers.”

With hopes of developing better disease management strategies, researchers are keen on understanding how these bacteria cause damage.

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