Detection of Pantoea ananatis in corn seeds on semi-selective medium

Maize white spot, caused by the bacterium Pantoea ananatis , is one of the main leaf diseases of maize in Brazil. However, until now, its presence in corn seeds has not been detected. In this study, P. ananatis was detected in corn seeds using a semi-selective culture medium. A bacterial suspension of P. ananatis was serially diluted ten-fold and plated on 523, YDC or semi-selective PA20 media, with or without the addition of methyl thiophanate. The detection of bacteria in seeds was evaluated in three seed lot samples, collected from field maize plants with white spot symptoms. Seed washings were prepared, ten-fold serially diluted and plated on the same three culture media. Addition of methyl thiophanate to 532, YDC and PA20 culture media did not inhibit bacterial growth. Pantoea ananatis was detected in two corn seed samples on YDC and PA20 media, which was confirmed by biochemical, physiological and molecular characterization as well as by pathogenicity tests. This is the first report of P. ananatis detection in corn seeds.