Biological evidence for practical immunity of apricot cultivar Harlayne to Plum pox virus

Abstract

Ten-year results of the practical immunity investigation of apricot cv. Harlayne are presented. Two-year-old trees of cv. Harlayne were inoculated by chip-budding with six different strains and isolates of Plum pox virus (PPV). PPV inoculated trees grew in the field and were evaluated from 2001 to 2011. No PPV symptoms appeared in the leaves of cv. Harlayne within ten years (2002–2011), and within eight years (2004–2011) in the fruits and stones. None of the six isolates of three different PPV strains was detected in the leaves and fruits by ELISA. Suckers of the rootstock Prunus myrobalana developed around cv. Harlayne trees in 2005–2011 were symptomless and ELISA was negative within seven years. New trees of cv. Harlayne obtained from tested trees by budding on PPV susceptible apricot rootstock MVA-2 in 2007 were PPV free from 2008 through 2011. The presence of PPV was proved by ELISA neither in leaves of cv. Harlayne nor in rootstock MVA-2.