Symptomless infection of barley seed by Rhynchosporium secalis

Rhynchosporium secalis, causal agent of scald of barley, generally overwint ers in barley residues. However, the pathogen can also infect seeds, produc ing typical scald symptoms. In the present study, symptomless seed-infectio n by R. secalis was demonstrated, using both cultural and polymerase chain reaction (PCR)-based detection assays. Seeds of the cv. Harrington without visible scald lesions were plated on lima bean agar supplemented with Benga l rose and streptomycin. In six independent trials, about 14% of seeds gave rise to colonies of R. secalis. A species-specific primer set, based on se quence analysis of the internal transcribed spacer regions of R. secalis, w as also used to detect symptomless seed-infection. The primer set did not a mplify the R. secalis diagnostic band in seed DNA extracts of the resistant cv. Seebe, but the scald pathogen was detected in symptomless seed DNA ext racts of the susceptible cv. Harrington. The results indicated that appreci able symptomless seed-infection by R. secalis can occur in barley and that diagnostic methods such as cultural and PCR-based assays would be useful to monitor it.