A rice gene that renders the crop resistant to several widely used beta-triketone herbicides has been identified, researchers report, revealing the genetic cause of herbicide susceptibility that has been identified in some important rice varieties. The newly discovered gene may be useful in breeding new herbicide-resistant crops. Rice is a staple food for more than 3.5 billion people and is among the world's most important crops. To meet the demands of the global food supply, the use of herbicides for controlling weeds is required for efficient crop production. While a useful herbicide is toxic to unwanted plants but harmless to the crop of interest, overuse of individual herbicides can lead to the emergence of weeds resistant to their once-deadly effects. Benzobicyclon (BBC), a beta-triketone herbicide developed for use in rice paddy fields, is effective against paddy weeds resistant to other herbicidal agents. However, BBC is also toxic to several high-yield rice varieties, according to the authors. To identify the gene responsible for BBC resistance or sensitivity, Hideo Maeda and colleagues performed map-based cloning on BBC-resistant and BBC-sensitive rice varieties, and they identified HIS1, a gene that confers resistance to BBC and other beta-triketone herbicides. According to Maeda et al., HIS1 encodes an oxidase that catalyzes and detoxifies BBC compounds. However, susceptible rice varieties inherited a dysfunctional his1 allele and harbor genetic mutations that disable expression of HIS1. What's more, similar functioning genes appear to be widely conserved in other important crop species, suggesting their potential value in breeding new herbicide-resistant crops.