Stem Rust (image) Burness Communications Caption Four new mutations of Ug99, a strain of a deadly wheat pathogen known as stem rust, have overcome existing sources of genetic resistance developed to safeguard the world's wheat crop. Leading wheat experts from Australia, Asia, Africa, Europe and the Americas, who are in St. Petersburg, Russia for a global wheat event organized by the Borlaug Global Rust Initiative, said the evolving pathogen may pose an even greater threat to global wheat production than the original Ug99. Credit Photo courtesy of Petr Kosina, the International Maize and Wheat Improvement Center (CIMMYT) Usage Restrictions Credit: Petr Kosina, CIMMYT Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.