DETECTION OF STRAWBERRY VIRUSES IN EGYPT

Abstract

As part of a USAID-MERC funded project, 'Disease-indexing and mass propagation of superior strawberry cultivars', an effort was made to evaluate the virus status of strawberries in Egypt. Diagnostic reverse transcription-polymerase chain reaction (RT-PCR) tests for Strawberry mottle virus, Strawberry crinkle virus, Strawberry vein banding virus (SVBV), Strawberry mild yellow edge virus (SMYEV), Strawberry chlorotic fleck virus, Strawberry necrotic shock virus, Strawberry latent ringspot virus, Apple mosaic virus, Fragaria chiloensis latent virus, Strawberry pallidosis associated virus (SPaV) and Beet pseudo yellows virus (BPYV) were developed and/or evaluated at the USDA-ARS laboratory in Corvallis, Oregon. Positive controls for the testing consisted of dried leaf samples of strawberries infected with each of the above viruses, shipped to Egypt and Israel under import permits. Collection of strawberry test samples was done in production fields (cultivars unknown) and from nuclear stock plants grown in Egypt ('Tamar' and 'Yael' originating from Israel). RNA extraction was carried out using Qiagen kits or a previously described protocol. Reverse transcription and polymerase chain reactions were carried as per manufacturer's recommendations. Amplicons were visualized after separation on an agarose gel and staining with ethidium bromide. The RT-PCR detection of viruses from RNA extracted from positive controls that were vacuum dried was successful for several but not all of the viruses used in this study. Thus, extracted RNA that can be shipped under ethanol may be a better positive control that dried tissue samples. Material carried back to the USA from Egypt as extracted RNA under ethanol was not impacted by storage at room temperature during transport. Initial testing of strawberry material from fields in Egypt showed that SMYEV, SVBV, BPYV and SPaV were detected in field samples. The plants tested from the nuclear stocks tested negative for each of the viruses tested.