Detection of sunblotch viroid from fruits of avocado cultivar 'Hass' using fluorescence-based qualitative real-time polymerase chain reaction
The presence of Avocado sunblotch viroid disease (ASBV) leads to massive losses in yield and fruit quality due to defects such as skin discolouration. This severely reduces the marketability of avocado fruits and ultimately profitability. Therefore, the detection of ASBV is important in controlling this disease, as symptomless trees pose a great danger in the spread of the ASBV. However, a rapid and more sensitive method for the routine detection of infected avocado tissues by ASBV is by qualitative real-time-polymerase chain reaction (qPCR) assay. Fruits produced from infected trees usually develop sunken white, yellow or pink blotches or streaks, and are usually small and deformed. Interestingly, there is no report of ASBV detection on 'Hass' avocado fruits. In this study, detection of ASBV on 'Hass' avocado fruits was based on qPCR reaction using cycling threshold values. Alternatively, the amplified PCR products were also detected using 2% w/v agarose gel electrophoresis for the presence of a 247 base pairs DNA fragment. Contrary to previous findings that the viroid was not necessarily detected in the leaves of avocado trees showing ASBV symptoms, in this study ASBV was detected in all fruits showing ASBV symptoms as well as in associated seeds.
Ncango, M.D., Dlamini, Z., Zulu, N.B. and Ngcobo, M.E. 2015. Detection of sunblotch viroid from fruits of avocado cultivar 'Hass' using fluorescence-based qualitative real-time polymerase chain reaction. Acta Hort. (ISHS) 1105:169-172
avocado extraction buffer, healthy green-skin, primers, RNA extraction, standard curve, unhealthy white-skin