Location: Sugarcane Research Unit
Title: Introduction of orange rust caused by Puccinia kuehnii into the Louisiana sugarcane industry Authors
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 18, 2013
Publication Date: June 1, 2013
Citation: Grisham, M.P., Haudenshield, J.S., Hoy, J.W., Glynn, N.C., Comstock, J.C., Hartman, G.L. 2013. Introduction of orange rust caused by Puccinia kuehnii into the Louisiana sugarcane industry. Phytopathology. (Suppl. 2):S2.53. Technical Abstract: The first observation of orange rust infecting sugarcane, caused by Puccinia kuehnii, in the Americas was in Florida in 2007. To monitor for the possible introduction of orange rust into Louisiana, visual surveys were initiated throughout the Louisiana sugarcane industry among plantings of cultivars known to be susceptible to the pathogen. Additionally, four wind-vane passive spore traps were positioned at four locations in Louisiana, and ionic spore traps were positioned at two locations. Real-time qPCR was used to analyze the weekly deposits in the spore traps. Urediniospores of P. kuehnii were detected in the spore traps in late-October and early-November 2010, which coincided with a period of high spore production in Florida. Symptoms of orange rust, however, were not observed in Louisiana sugarcane until June 2012. The identity of P. kuehnii was verified using the species-specific qPCR assays. Although extensive surveys were conducted throughout 2012, observations of orange rust were limited to one cultivar, HoCP 05-961, a recently released cultivar with limited distribution. Initially, disease incidence and severity were low, increasing gradually throughout the growing season, becoming severe in November at two locations. Because disease symptoms only increased in severity late in the harvest season, the economic impact is unknown. Studies have been designed to determine what effect orange rust has on sugarcane yield.