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ARS Home » Southeast Area » Miami, Florida » Subtropical Horticulture Research » Research » Publications at this Location » Publication #362678

Research Project: Conservation, Evaluation, and Distribution of Sugarcane, Mango, Avocado and Other Subtropical and Tropical Genetic Resources and Associated Data

Location: Subtropical Horticulture Research

Title: A highly sensitive method to detect Avocado Sunblotch viroid (ASBVd) in avocado trees for maintenance of viroid-free avocado germplasm collections

item Kuhn, David
item Freeman, Barbara - Barbie
item GREERING, ANDREW - University Of Queensland
item CHAMBERS, ALAN - University Of Florida

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2019
Publication Date: 6/4/2019
Citation: Kuhn, D.N., Freeman, B.L., Greering, A., Chambers, A. 2019. A highly sensitive method to detect Avocado Sunblotch viroid (ASBVd) in avocado trees for maintenance of viroid-free avocado germplasm collections. Viruses. 11(6):512.

Interpretive Summary: Avocado is the second most important tree crop in Florida after citrus. Avocado Sunblotch viroid (ASBVd) is a disease specific to avocado that either causes yellow depressed areas on the fruit or is symptomless. USDA-ARS SHRS has a germplasm collection of avocado that is distributed to clients and stakeholders through GRINGlobal. We cannot distribute ASBVd infected material, so we need a highly sensitive assay to detect viroid infection. In addition, our collection is threatened by another disease, laurel wilt, so we want to make a back up collection at the USDA-ARS PBARC station in Hilo, HI. However, Hawaii also has an avocado production industry and currently has no ASBVd infected trees. This is another reason we need a highly sensitive assay for ASBVd. We report here the development of such an assay and its use in removing all viroid infected trees from the SHRS collection. This allows us to distribute viroid free avocados and we have completed our back up collection at PBARC. This research is of interest to avocado producers, nurserymen and curators of avocado collections.

Technical Abstract: The USDA-ARS Subtropical Horticulture Research Station in Miami, FL holds a large germplasm collection of avocado (Persea americana). The recent threat of infection by laurel wilt has encouraged the creation of a backup collection in a disease-free site. Creating the backup collection is complicated by the infection of some of the germplasm with the Avocado Sunblotch viroid. Infected trees are frequently symptomless. Although a reverse-transcription based assay already exists and has been used to assay all germplasm on the station, some trees showed inconsistent results. We have developed a more highly sensitive and specific assay involving pre-amplification of the entire viroid cDNA followed by detection using real time PCR and a TaqMan assay. A second screening of all germplasm has identified more ASBVd infected trees and allowed us to confidently remove these trees from the station and proceed with the creation of viroid-free backup collection.