LAUSR

A polymerase chain reaction (PCR) based assay was compared with assay involving traditional microbiological tests to detect and identify Clavibacter michiganensis subsp. insidiosus (Cmi) inside plant tissues following artificial inoculations. Primers for Cmi detection were selected from the Cmi insertion sequence IS 1122. External disease symptoms on the tops and histological symptoms on the cross-sections of the roots were evaluated visually and microscopically during two years after inoculation. Extracts were prepared from samples collected from the tops and roots of lucerne plants for both PCR and microbiological analyses. Colonies which morphologically resemble to be Cmi were tested using PCR. Cmi bacteria were detected in stem and root tissues using both methods. The PCR can rapidly detect Cmi in lucerne plants showing histological disease symptoms on the cross-sections of the roots. Further work is needed to detect reliably Cmi in lucerne plants with latent infections and in infected seeds or contaminated seed lots.