Single-strand conformation polymorphism (SSCP), cloning and sequencing reveal a close association between related molecular variants of Grapevine virus A (GVA) and Shiraz disease in South Africa

When a recently discovered 234-nt fragment of the Grapevine virus A (GVA) genome, located in ORF3, was used in single-strand conformation polymorphism (SSCP), it produced patterns of DNA bands which were indicative of GVA variants of molecular group II. This technique of rapid identification of variants of group II was applied to the study of GVA variants in various grapevines with different Shiraz disease (SD) status. The results, supported by nucleotide sequence data, revealed that GVA variants of molecular group II are closely associated with SD in South Africa, and showed that variants of group III are commonly present in SD-susceptible grapevines that consistently do not exhibit symptoms of this disease.