Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: 11/20/2007
Publication Date: 12/10/2007
Citation: Vandemark, G.J. 2007. Controlling Root rot of Alfalfa Caused by Aphanomces and Phytophthora. Forage Focus.Dec. 2007. pp. 8-9.
Technical Abstract: Alfalfa is the fourth most important crop in the United States in terms of both cultivated acreage (greater than 22 million) and annual production value (greater than $6 billion). Alfalfa is typically grown as a perennial crop, with stands cultivated for the three or more consecutive years. Effective control of root rot and crown rot diseases is critical to stand longevity, productivity and profitability. Aphanomyces root rot (ARR) and Phytophthora root rot (PRR) are among the most destructive soilborne diseases of alfalfa. These two diseases are caused by the soilborne water molds Aphanomyces euteiches and Phytophthora medicaginis, respectively. Crop rotation does not effectively control these diseases because both pathogens produce spores that can survive for years in soil or in infected root debris. The most economically effective method for controlling diseases of alfalfa is to grow alfalfa varieties that are resistant to multiple diseases. At the USDA-ARS Vegetable and Forage Research Unit, located in Prosser, WA, investigators are developing alfalfa populations that have high levels of resistance to multiple diseases, including Aphanomyces root rot and Phytophthora root rot. DNA-based assays have been developed for detecting and quantifying both A. euteiches and P. medicaginis in infected plants. These assays can help breeders to more precisely identify immune or highly resistant plants. They also provide useful tools for investigating basic processes of disease development in plants that are simultaneously infected with multiple pathogens.