Evaluation of the Susceptibility of Several Plum (Prunus Domestica L.) Cultivars to Plum Pox Virus (Ppv) Infection in the Field. Sharka-Like Symptoms Observed on 'Jojo' Fruit are Not Related to PPV

Susceptibility of plum cultivars: 'Katinka', 'Jubileum', 'Diana', 'Valjevka', 'Żółta Afaska', 'Elena', 'Jojo', 'President', 'Vision', and 'Węgierka Zwykła' (Pozegaca type, included as reference, highly susceptible cultivar) to aphid-vectored Plum pox virus (strain D), was evaluated. The trees were grown for 7-8 years in the field characterized with high infection pressure. 'Katinka' and 'President' showed susceptibility even higher than 'Węgierka Zwykła'. 'Vision' and 'Valjevka' showed relatively low susceptibility with less than 30% of trees becoming infected. All 'Jojo' trees remained free from ELISA-detectable amounts of PPV, although a high percentage of the fruit of this cultivar showed sharka-like symptoms on stones and fruit flesh. The reason for that phenomenon is not known.