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

Abstract

Polák J., Komínek P. Keywords: stone fruits; immunity; PPV strains; symptoms; bud transmission; susceptible rootstock, runnersThe best protection against quarantine Plum pox virus (PPV) is to grow immune or resistant cultivars of stone fruits. Dosba et al. (1992) proved apricot cv. Harlayne to be immune to PPV. We have confirmed the immunity of apricot cv. Harlayne to PPV by grafting onto five years old trees of apricot cv. Vegama, susceptible and infected with PPV-M. Cultivar Harlayne was certified as immune to PPV-M strain. No virus was detected either by ELISA or IC-RT-PCR, nor in the grafted indicator Prunus tomentosa (Polák et al. 1997). Biological, serological, and molecular demonstrations confirmed the immunity of cv. Harlayne to the most pathogenic PPV-M strain. There are seven recognised strains of PPV: M, D, Rec, EA, C, W, and T. Three of them M, D, and Rec are present in the territory of the Czech Republic. Since the resistance or immunity of cultivars to plant viruses can be strain-specific, the behaviour of cv. Harlayne against six different isolates of three PPV strains present in the CR was studied in the field trial. Preliminary results of three-year testing proved that no symptoms appeared on the leaves of apricot cv. Harlayne, and ELISA did not prove the presence of PPV strains in leaves (Polák et al. 2005). Fruits and leaves of apricot cv. Harlayne were tested by ELISA and RT-PCR and symptoms observed in another three years. Six-year evaluation carried out in the Czech Republic proved the immunity of apricot cv. Harlayne to the six different PPV strains of groups PPV-D, PPV-Rec, and PPV-M. No symptoms appeared in the leaves and fruits,