Valutazione della resistenza al PPV ceppo M in germoplasma peschicolo

Evaluation of the resistance to PPV-M strain in peach germplasm ‘Sharka’, caused by Plum pox virus (PPV), is the most serious disease of stone fruits with a severe impact on quality and quantity production. Because of the lack of natural resistance in commercial peach germplasm, breeding programs have been carried out using cultivated Prunus species related to peach (Prunus dulcis) and wild Prunus species (P. davidiana), showing PPV resistance. In particular, a quantitative resistance against PPV was found in P. davidiana. In this work selected peach offsprings (no. 122), obtained from crosses between commercial peach varieties and genotypes putative tolerant or resistant to PPV, were evaluated to determine the susceptibility to the virus. The reaction to PPV inoculation was experimentally evaluated comparing symptoms expression with the results of two specific diagnostic assays (ELISA and real-time RT-PCR). All symptomatic selections (101/122) resulted positive in ELISA test and were classified as ‘sensitive’, whereas 21 out of 122 tested did not show any symptom. Four years after inoculation only 12 selections confirmed to be asymptomatic and were positive in real-time RT-PCR. On the basis of presence/absence of symptoms on GF305 rootstock and positive/negative results obtained in ELISA test, these 12 genotypes were classified as tolerant, highly tolerant or resistant to PPV, strain M.