Susceptibility of SEO/'Harlayne' type resistant apricot cultivars to PPV-T

Plum pox virus (PPV) is one of the most detrimental diseases of the Prunus species. The use of genetic resistance is the most promising solution for the control of the virus. To date, in apricot the resistance has only been found in the North American germplasm. The American cultivars ‘Stark Early Orange’ (SEO), ‘Goldrich’, ‘Harlayne’, ‘Stella’, and ‘Harcot’ are known as resistant against to PPV-D and M strain, both of which are the most common strains in Europe. These cultivars host a major locus located on the Linkage Group One (LG1) accounting for 70% of PPV resistance. In a previous study, Turkish apricot germplasm was screened for three markers which are known to be linked to the resistance locus on LG1 and five accessions in the Turkish collection were identified to host the markers. Here we report the first two years results of the biological test applied to the same collection. Biological test was commenced in Kayseri in 2012 by graft inoculating the accession with a PPV-T (Turkey) strain. After examinations in two consecutive years, we observed that SEO, ‘Harlayne’, ‘Harcot’ and the five accessions of Turkish apricot germplasm with resistance markers fail to show resistance to PPV-T. However, in the third year of observation the symptom level decreased on the resistant accessions.