A mild strain of Grapevine leafroll-associated virus 3 is present in desirable clones of Crimson seedless table grapes in Western Australia

Abstract

We have obtained superior clones of Crimson Seedless (CS) table grapes in Western Australia (WA) by introducing combinations of the following viruses into the plants: a mild strain of Grapevine leafroll-associated virus 3 (GLRaV-3), GLRaV-9 and -5 and Grapevine virus A. We detected two strains of GLRaV- 3 in different clones of Crimson Seedless. One strain (GLRaV-3-s) produces a severe phenotype, it spreads naturally and is associated with poor quality grape berries. The other strain (GLRaV-3-m) gives a mild phenotype and is associated with larger, crisper and heavier berries as compared to the virus-free CS clone 8210. The nucleotide sequences of the coat protein genes of the mild and severe strains were compared and revealed a high degree of homology. Further sequencing analysis is in progress. A molecular assay is now available to differentiate between these two strains of GLRaV-3 and this will enable us to discard inferior plants infected with the severe strain.