Gene sequencing targets witchweed and other destructive parasitic plants

An international research team, including a University of California, Davis, plant scientist, is using the molecular magic of gene sequencing and transfer to break the stranglehold of witchweed and other parasitic plants that annually cause billions of dollars in crop losses around the world.

Joining forces through the Parasitic Plant Genome Project, funded by the National Science Foundation, UC Davis Professor John Yoder and colleagues are identifying the genome-wide changes that have evolved to equip this intriguing but often devastating group of wild plants to develop their parasitic lifestyle.

"We know that parasitic plants evolved from non-parasitic plants, so we take an evolutionary approach and ask, 'What are the genetic changes that make a plant parasitic, and what are the genetic consequences once a plant becomes a parasite?'" said Yoder, whose lab in the UC Davis Department of Plant Sciences is contributing to the Parasitic Plant Genome Project. "The next stage is to identify critical parasite genes and pathways and use this information to develop parasite-resistant crops," he said.

In a May their cover article for the journal Molecular Plant-Microbe Interactions demonstrated a new strategy for engineering within host plants a killer DNA molecule that is toxic to at least one species of Orobanchaceae. This family of almost 2,000 parasitic plant species includes some of the world's worst agricultural pests, notably Striga or "witchweed" and Orobanche, also known as "broomrape."

Striga, for example, has a reputation for covertly destroying crop fields. By the time the purple flowers of this parasitic weed have bloomed, the field is already ruined. Removed from the soil, Striga can return decades later through dormant seeds. The infestations are particularly devastating to staple crops like rice, maize, millet and sorghum in sub-Saharan Africa and the Middle East.