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ARS Home » Midwest Area » West Lafayette, Indiana » Crop Production and Pest Control Research » Research » Publications at this Location » Publication #141548
Title: A RAPID PCR-BASED METHOD TO DETECT MAGNAPORTHE ORYZAE FROM INFECTED PERENNIAL RYEGRASS

Author
item HARMON, PHILIP - PURDUE UNIVERSITY
item Dunkle, Larry
item LATIN, RICHARD - PURDUE UNIVERSITY

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2003
Publication Date: 9/10/2003
Citation: HARMON, P.F., DUNKLE, L.D., LATIN, R.X. A RAPID PCR-BASED METHOD TO DETECT MAGNAPORTHE ORYZAE FROM INFECTED PERENNIAL RYEGRASS. PLANT DISEASE. 2003. v. 87. p. 1072-1076.

Interpretive Summary: Gray leaf spot is a persistent and serious disease of perennial ryegrass turf in most parts of the midwestern U.S. Accurate identification of the causal agent is critical for disease management but is often confounded by the presence of other fungi that cause similar symptoms. We developed a PCR-based assay to detect and identify the fungal pathogen, Magnaporthe oryzae, in diseased grass leaves without expensive and time-consuming DNA extraction steps. The procedure is specific, rapid, and accurate and requires only 4 to 8 hours compared to 48 hours or longer with methods that involve isolating and culturing the fungus. This method will reduce the time required and ambiguity inherent in disease diagnosis based on symptoms alone or on culturing the pathogen. Disease diagnosticians will use the information and the method to make accurate and timely recommendations to turf grass managers regarding fungicide applications, which in turn will result in more judicious use of fungicides.

Technical Abstract: Gray leaf spot of perennial ryegrass caused by Magnaporthe oryzae is a serious disease in the Midwestern U.S. Outbreaks normally occur from mid- to late summer and are especially severe on athletic fields and golf course fairways. Symptoms of gray leaf spot can be confused with those of other fungal diseases that also are common during periods of high temperatures and ample moisture. Because turf managers must select appropriate fungicides for remedial treatment, accurate and timely identification of the pathogen is critical for disease management. A PCR-based method was developed to detect M. oryzae in infected perennial ryegrass tissue. The method utilizes a commercially available kit for isolation and amplification of plant DNA from leaf tissue. The kit protocol was modified and found to be reliable for the extraction of M. oryzae DNA from infected perennial ryegrass. Primers were designed to amplify a 524-base pair fragment of the Pot2 transposon present in multiple copies in the genome of the perennial ryegrass pathogen. The method amplified amounts of DNA as low as 5 pg and consistently and specifically detected the fungus in single diseased leaf blades. The total time required fro detection was approximately 4 to 8 hours. The procedure was used successfully to identify the pathogen in field samples of diseased perennial ryegrass.