Dot-blot procedure with [32P]DNA probes for the sensitive detection of avocado sunblotch and other viroids in plants.

Avocado sunblotch viroid (ASBV) has been detected down to a level of about 20 pg per gram fresh weight of leaves by the use of a dot-blot hybridization procedure and partially purified nucleic acid extracts. Three [32P]DNA probes were compared, two prepared from full-length ASBV clones in the single-strand M13mp93 vector and the other by primer extension on purified ASBV. All three probes gave the same sensitivity of detection of ASBV. The methods developed have also been used successfully for the routine detection of potato spindle tuber viroid, citrus exocortis viroid, and coconut cadang cadang viroid.