DETECTION OF AVOCADO SUNBLOTCH VIROID AND ESTIMATION OF INFECTION AMONG ACCESSIONS IN THE NATIONAL GERMPLASM COLLECTION FOR AVOCADO

Reverse transcription-polymerase chain reaction (RTPCR) was used to determine the incidence of infection by avocado sunblotch viroid (ASBVd) in the germplasm collection at the National Germplasm Repository at Miami (NGR-Mia). Of the 429 avocado plants growing at the repository, 81 (18.9%) are infected with the viroid. The 429 plants represent 237 accessions. There are multiple plants of some accessions and for 42 accessions (17%) every plant is infected with the viroid. There was no apparent relationship between host race and the incidence of infection. Symptoms of sunblotch disease on avocado (Persea Americana Mill.) manifest as a general decline of tree vigor with sunken, yellow areas on the fruit that lessen its marketability. The disease was first described as infectious, rather than physiological,