An apple chlorotic leaf spot virus isolate from ornamental dwarf flowering almond (Prunus glandulosa 'Sinensis'):: Detection and characterization

An apple chlorotic leaf spot virus (ACLSV) isolate was detected by TAS-ELISA and RT-PCR in an ornamental dwarf flowering almond (Prunus glandulosa Thunb.). This plant, maintained at the Centre for Plant Health, Sidney, B.C., Canada, has been showing transient leaf symptoms during the spring seasons. A 390-bp fragment and a 1,350-bp product, in the RNA polymerase and the coat protein viral coding regions, respectively, were amplified by RT-PCR from the infected plant. A sequence comparison of the 390-bp fragment of this ACLSV isolate (designated as AL1292) with other published isolates, revealed a similarity of 81% to 84% at the nucleotide level and 88% to 100% at the amino acid level. In contrast to other ACLSV isolates, AL1292 has an exceptionally narrow range of experimental herbaceous and woody hosts, as determined by mechanical and graft inoculation assays. These standard bioassays may not be effective for the detection of the AL1292 isolate because of its limited host range. The results we report in this paper confirm R glandulosa as a natural host of this virus. Currently it is not known how ACLSV is spread, other than by bud-grafting and possibly by root grafts. The use of virus-tested source plants for the preparation of planting material will minimize its spread.