DNAeDNA similarity analysis (DNA reassociation)combined with random amplified polymorphic DNAanalysis were used by Rippere et al. (1998) and Harrisonet al. (2000) to study the relationship of numerous strains/isolates of milky disease bacteria; these methods clearlysegregated the isolates into P. popilliae or P. lentimorbus.However, more recent studies (Pettersson et al., 1999;Dingman, 2008, 2009) have used comparative analysis of16S rDNA for species identification and classification,a method that has become the standard for identificationand classification of bacteria in general. While 16S rRNAhas successfully defined milky disease causing species,strain differentiation requires other methods. Macdonald& Kalmakoff (1995) used PFGE to differentiate NewZealand isolates of P. popilliae from the USA biocontrolstrain, and studies of North and South American strainsshowed that the technique would be used for monitoringof individual isolates (Correa & Yousten, 2001). RFLPand 16S rDNA sequence comparison has further beenused (Dingman, 2009) to examine variation according togeographic region of isolation.
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