Detection of plum pox virus in root and bark samples from dormant plum trees

An immune-capture polymerase chain reaction (IC-PCR) protocol and ELISA were compared for their effectiveness in detecting plum pox virus (PPV) in dormant plum material. Although the IC-PCR was about 1000 times more sensitive than ELISA, PPV was detected by ELISA in 71-80% of bark samples collected in December. January and March from pot-grown rootstock trees inoculated with PPV the previous March, compared to 85-86% detection in the same samples by IC-PCR. In similar samples from one year old shoots taken from infected branches of orchard trees, 66-81% were positive by ELISA compared to 81-87% by IC-PCR. With bulked samples taken from the fibrous roots of the pot-grown trees, PPV was detected in 92-100% of samples by IC-PCR in winter compared to only 38-65% by ELISA; the extra sensitivity of IC-PCR may offer a reliable method for assessing infection in young trees and rootstocks lifted from nursery rows.