IMMUNOCAPTURE POLYMERASE CHAIN-REACTION FOR THE DETECTION AND CHARACTERIZATION OF CACAO SWOLLEN SHOOT VIRUS-1-A ISOLATES

Oligonucleotides derived from the flanking regions of the putative coa t protein gene of the cacao swollen shoot badnavirus isolate 1A (CSSV- 1A) were able to prime the synthesis of specific products directly fro m extracts from CSSV-1A-infected leaves by immunocapture polymerase ch ain reaction (IC-PCR), following trapping of virions with polyclonal a ntibodies to CSSV-1 A. CSSV isolates serologically distinct from CSSV- 1A were not detected by IC-PCR when the CSSV-1A-derived primers were u sed following trapping with homologous antisera. IC-PCR was at least 1 00-fold more sensitive than double antibody sandwich (DAS)-ELISA in co mparative tests on samples from greenhouse-grown cacao plants. The sup erior sensitivity of IC-PCR over DAS-ELISA was confirmed in attempts t o detect and identify CSSV-1 A isolates in field samples and permitted detection of CSSV-1A isolates even in symptomless leaves from plants showing stem swelling only. The IC-PCR products obtained from four ran domly selected field samples were sequenced and shown to contain a reg ion of the CSSV-1 A genome where ORF X overlaps ORF 3. Analysis of the partial amino acid sequences deduced from ORF 3 and ORF X of the four field isolates revealed a considerable variation in these CSSV-1 A ge ne products.