PCR-Based Detection of Cephalosporium gramineum in Winter Wheat

A polymerase chain reaction (PCR) assay was developed amplifying a 496-bp fragment of the internal transcribed spacer region of Cephalosporium gramineum genomic DNA at concentrations of 100 fg/μl. Winter wheat seed and seedlings were collected from field plots where C. gramineum was present. Seed was tested by PCR using 20-seed samples bulked for DNA extraction. Estimates of seed infection, based on isolation of the pathogen on semiselective medium and PCR, were comparable at 0.18 and 0.13% of winter wheat 'Stephens' (P = 0.6042), and 0.45 and 0.58% of experimental line WA7970 (P = 0.5636), respectively. PCR differentiated between plants with well-developed symptoms of Cephalosporium stripe and noninoculated plants. Positive PCR was obtained from 22% of asymptomatic leaf blades from inoculated plants. We found no false positives when PCR and C. gramineum isolation on a semiselective medium were performed using tissue from the same leaf. The PCR assay has potential to diagnose Cephalosporium stripe disease prior to the appearance of symptoms. Negative PCR for some samples from which C. gramineum was isolated suggests that C. gramineum may be present below the level of detection in some asymptomatic leaves. This PCR assay may be useful for investigations into C. gramineum infection of wheat.