Seeds of Parasitic Plants Can Detect Hormones Released by Roots of Host Plant, Enabling Identification, and Stimulating Germination and Attack; System Developed by Duplications and Evolution of Gene Used to Sense Fire; Related Crop Losses Now in Billions

An international team of researchers, led by scientists at the University of Georgia (UGA), has discovered how parasitic plants, which steal their nutrients from other living plants, evolved the ability to detect and attack their hosts. The team’s findings, published in the July 31, 2015 issue of Science, could lead to new techniques to control the destructive plant parasites. The article is titled “Convergent Evolution of Strigolactone Perception Enabled Host Detection in Parasitic Plants.” There are thousands of parasitic plant species, but the most burdensome for humans are those that infiltrate farmland and destroy crops. Parasite infestations reduce crop yields by billions of dollars each year, particularly in developing nations where access to advanced herbicides and other control methods is limited, according to the researchers. "In the simplest terms, these are plants that eat other plants," said Dr. David Nelson, co-author of the Science article and Assistant Professor of Genetics in UGA's Franklin College of Arts and Sciences. "The seeds of some parasitic plants, like witchweed (image is of purple witchweed) for example, can lie dormant in soil for more than a decade, waiting to grow until they detect the presence of a host. We wanted to understand how the parasites know other plants are nearby so we could develop new ways of combating them." As plant roots grow, they release hormones called strigolactones into the soil. This is a signal that normally helps fungi form a beneficial connection to the plant, in which they each trade nutrients. But the seeds of parasitic plants also possess the ability to sense strigolactones, which prompt them to germinate, attach to the host root, and syphon off nutrients.
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