Scientists Identify Witchweed Resistance Gene

Researchers from the University of Virginia in the U.S. have successfully identified a gene in cowpea that confers resistance to the parasitic weed Striga. Also known as witchweed, Striga infests some 50 million hectares of cereal crops and is responsible for more than USD 7 billion worth of crop damage every year in Africa. Underground witchweed parts connect to crop roots and feed on them, reducing yield dramatically and sometimes even destroying entire fields. Striga attacks numerous crops, including cowpea, a major food and forage legume in the Sahel of West and Central Africa. Controlling the parasitic weed through conventional techniques is a challenge. Striga is known to produce thousands of seeds that can stay dormant in the soil for years.

The Striga resistance gene, RSG3-301, encodes a protein localized in the peripheral plasma membrane that serves as a guard molecule against Striga attachment and penetration. Silencing this gene in resistant varieties resulted to susceptibility to Striga attacks. Cowpea plants incapable of expressing RSG3-301 "failed to mount a resistance response when challenged with a particular Striga race and allowed the weed to penetrate the endodermis and to establish xylem-xylem connections with the host vascular system," the scientists wrote in a paper published by Science.

There are at least seven Striga races, each with the capability of adapting to different cowpea varieties. The researchers are now trying to develop cowpea plants that are resistant "across the board."

The paper is available at http://dx.doi.org/10.1126/science.1174754 For more information, read http://www.virginia.edu/uvatoday/newsRelease.php?id=9543