Plum pox virus (PPV) belongs to the genus Potyvirus that contains the largest number of virus species infecting plants. Its virus genome has been extensively characterised and sequenced. However, few data are available on its interactions with woody host plants. We therefore focused, in the past 4 years, both on the cellular and molecular aspects of the compatible and incompatible Prunus /PPV interactions. GFP (Green fluorescent protein)-tagged PPV and in situ hybridisation were used to compare the localization of viral particles in stems and leaves of susceptible and resistant apricot cultivars. In parallel, molecular tools were developed through the cloning and characterization of polymorphic, homologous resistance genes and of candidate genes involved in the expression of Prunus /PPV interactions. Candidate genes are currently used to target genomic regions involved in resistance or susceptibility and to identify molecular markers indispensable for further marker assisted selection for resistance to sharka disease.

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Sharka (Plum pox) is considered one of the most devastating diseases of stone fruits in terms of agronomic impact and economic importance. The response of several apricot hybrids was evaluated over the vegetative period of 2010 by visual monitoring of symptom development and by serological and molecular methods. After two cycles of study, all the replicates of ‘Mari de Cenad’, ‘Traian’ and ‘Tabriz’ showed sharka symptoms while the replicates of ‘Stark Early Orange’ and NJA 2 did not show any symptoms and were not ELISA-positive. The resistant progenitors (‘Stark Early Orange’, NJA17, NJA42 and NJA2) were able to transmit PPV resistance to their descendants, in agreement with previous results (DOSBA et al, 1994, MARTINEZ-GOMEZ et al, 2000; AUDERGON et al, 1994). The genetic control hypotheses for PPV resistance in apricot referenced by different authors considered the resistance allele as dominant. Romanian apricot F1 and F2 progenies evaluated were classified into two groups: susceptible to PPV and resistant to PPV. After that the most important genotypes were grafted onto infected GF 305 (considered as indicator for PPV) in greenhouse conditions. The final step is the introduction and development of the marker-assisted selection (MAS) in PPV resistance F1 and F2 progenies in apricot Romanian genotypes. DNA was isolated from all hybrids and parent genotypes. These samples will be used to implement the molecular markers for identification of genes linked to plant response to PPV infection.

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