PRELIMINARY RESULTS OF TRIALS EVALUATING THE BEHAVIOUR TO PLUM POX VIRUS OF DIFFERENT APRICOT CROSSES

This work reports the preliminary results of Plum pox virus (PPV) infection on apricot seedlings belonging to two different crosses from a breeding program of the Universities of Milan and Bologna (Italy): Lito × BO 81604311 (121 seedlings) and Harcot × Reale d’Imola (116). An improved protocol developed by the Department of Plant Protection and Applied Microbiology of University of Bari was applied. The sequential steps of the protocol are: 1) bud grafting onto myrabolan and Prunus persica GF305; 2) chip-bud inoculation on the above rootstocks with known isolates of PPV-M and PPV-D (both strains for the first cross and only D-strain for the second one); 3) visual inspections on rootstock and apricot for leaf symptoms expression: during each growth cycle leaf symptoms were scored from 0 (no symptoms) to 3 (higher intensity of symptoms); and 4) testing by ELISA and IC-RT-PCR. The protocols provides for the observation of the seedlings until the fruiting stage. The results after two vegetative cycles since the inoculation demonstrate: a) most of the seedlings of the cross Harcot × Reale d’Imola showed symptoms and were ELISA-positive since the first controls (78% and 42% in presence, respectively for PPV-M and PPV-D strain); b) most of the seedlings belonging to the cross Lito × BO 81604311, in the first vegetative cycle after inoculation (2005), showed symptoms since the earliest visual inspection and were ELISA-positive for both strains (92% and 73% in presence, respectively for PPV-M and PPV-D strain). In springtime 2006 a greater number of seedlings, infected with PPV-M and PPV-D strains, were symptomless and ELISA-negative; the myrabolan revealed to be an effective indicator, showing symptoms since the first visual inspections after two-three weeks since sprouting.