The incidence and strain variation of Apple stem grooving and Apple stem pitting viruses in Australian pome fruit.

摘要

A survey of key pome fruit growing districts of Australia during 2004-05 indicated that Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV) were widespread in Australia. Using RT-PCR, ASPV and ASGV were detected in 152 of the 173 samples (87.9%) and 121 of the 173 samples (69.9%) of trees tested, respectively. Significant variation was observed between the isolates of each virus and these isolates were distinct from isolates reported in other countries. Sequence analysis of the 1.20-kb region of the of the 3' end of ORF1 and ORF2 of the ASPV genome of 5 Australian isolates identified a sequence variation ranging from 76-96% sequence similarity. A comparison of the 3'terminal end of ORF1 and ORF2 regions of the ASPV genome indicated that the 3' terminal end of ORF1 was generally less conserved than that of ORF2. A 2.5-kb region in the ASGV genome of 5 Australian isolates, which encoded the 3' end of ORF1 as well as ORFs 2 and 3, indicated that all the isolates were very closely related (98% or greater sequence similarity). The alignment of the published ASGV sequences and several Australian isolates identified in this survey showed that ORF3 (coat protein) and the 3' terminal region of the ASGV genome are more highly conserved (greater than 90% similarity) than the 3' end of ORF 1 and ORF2 (less than 86% similarity). The results showed that the genetic variation between viral strains can affect the reliability of the molecular tests for ASGV and ASPV.