PCR identification of Erwinia stewartii and its comparison with two other methods

Erwinia stewartii (Dye) causes Stewart's Wilt, a seed transmitted bacterial disease of maize. This pathogen, of quarantine importance, is responsible for serious crop losses in many tropical countries. At present, seed health tests are time consuming and lack sensitivity. This paper describes the de velopment of a polymerase chain reaction (PCR) test to identify E. stewarti i and the comparison of this with two other seed health testing methods (ni grosine selective medium and ELISA). PCR with arbitrary primers was used to identify a DNA fragment far use as a probe to detect E. stewartii isolated from maize seed. Specific nested primers for E. stewartii were designed fr om the partial sequence of the E. stewartii probe. These primers were highl y specific and did not cross-react with other Erwinias or a wide of range o f bacterial isolates obtained from maize seed samples. Identification of th is pathogen from cultured cells is rapid using PCR and can be done in less than a working day (5 hours). The sensitivity of the nested PCR is sufficie nt to amplify from approximately ten bacterial cells.