Manifestation of Practical (Field) Resistance of Apricot (Prunus armeniaca) to Plum Pox Virus (Sharka Virus, PPV)

The investigation was aimed at the receptivity and possible reactions of apricot (Prunus armeniaca) to plum pox virus (sharka virus, PPV) widely spread not only in the orchards but in the uncultivated terrains on the territory of Bulgaria, where fruit trees of the genus Prunus grow. Field observations of manifestation of plum pox (sharka) disease were carried out during the period of 2015–2017. They covered trees of plum (P. domestica), wild plum (P. cerasifera), peach (P. persica) and apricot (P. armeniaca). Apricot seedlings grown in the yard nearby the Plant Protection Department of ISSAPP were also included in the investigation. The seedlings originated from pits with and without sharka symptoms. A double antibody sandwich enzyme linked immunosorbent assay (DAS ELISA) was used for detecting the viral pathogen. The spread of plum pox disease was visually identified in all investigated orchards. Plum trees were the most contaminated. Single cases of sharka on wild plum, peach and apricot trees were also observed. During the period of investigation apricot seedlings remained healthy and the results of DAS ELISA were negative. Apricot seedlings were not receptive to PPV in field conditions when the insects (aphids) were natural vectors of the viral infection. The apricot trees could have been infected through infected rootstock (P. cerasifera). The results confirmed that apricot generative posterity remained free of PPV.