Transgenic, 'HoneySweet' plums inoculated with Plum pox virus, recombinant strain (PPV-Rec) alone, PPV-Rec + Apple chlorotic leafspot virus (ACLSV), PPV-Rec + Prune dwarf virus (PDV), and PPV-Rec + ACLSV + PDV were grown in an open field under high and permanent infection pressure both from graft inoculation and natural aphid vectors for 8 years. 'HoneySweet' control trees were non-graft-inoculated trees. Plants were monitored by symptomology, DAS-ELISA, semiquantitative (SQ)-ELISA, and real-time (RT)-PCR. Inoculum shoots showed severe PPV symptoms from the first year after inoculation throughout the study. Mild PPV symptoms appeared in some of the basal leaves of graft-inoculated 'HoneySweet' trees in the second year following inoculation. During the following six years, even these mild and isolated symptoms on 'HoneySweet' trees diminished. The presence of PPV in these basal areas of 'HoneySweet' trees was confirmed by ELISA, ISEM, and RT-PCR. Relative concentration of PPV determined by SQ-ELISA and by RT-PCR was lower than in leaves of inoculum shoots. No difference in PPV symptoms was observed between PPV-Rec, and combinations PPV-Rec with other viruses. While no symptoms of ACLSV appeared during the study, ACLSV was detected by ELISA and RT-PCR. No symptoms of PDV appeared and PDV was not detected. 'HoneySweet' trees exposed to natural aphid-vectored PPV were not infected. Fruits of 'HoneySweet' were qualitatively and quantitatively compared with fruits of 'Stanley' and 'Domaci svestka' in 2010 from noninfected trees of 'HoneySweet' and fruits from 'HoneySweet' trees graft-inoculated with PPV-Rec + ACLSV + PDV were both of high quality and comparable to, or for certain characteristics, of higher quality than fruit of the commercial cultivars which were evaluated.Read less <