A method based on the hybridisation of tissue imprints was developed for ro
utine indexing of citrus viroids. For maximum sensitivity and reliability,
the inoculation of Citrus medica (Etrog citron) as a viroid amplification h
ost is required. Hybridisation against Digoxigenin-labelled RNA- or DNA-pro
bes followed by detection of viroid-probe hybrids using anti-DIG-alkaline p
hosphate conjugate and the chemiluminescence substrate CSPD was suitable fo
r the detection of all citrus viroids with the same sensitivity as other av
ailable methods. The overall process is extremely simple and allows quick a
nalysis of large numbers of samples by easily trained personnel and minimum
equipment.