Relative concentration of plum pox virus in leaves and flowers of some Prunus species and cultivars

The relative concentration of plum pox virus (PPV) in leaves and flowers of plum, damson, myrobalan, blackthorn, apricot and peach trees was determine d by enzyme-linked immunosorbent assay(ELISA) and expressed as the lowest d ilution with positive reaction. Significant differences in relative PPV con centration were found in leaves among individual Prunus species naturally o r artificially infected with the virus. The highest relative PPV concentrat ion was found in blackthorns (7.81 x 10(-4)), common plum and apricot (1.56 x 10(-3) for the both latters). Wild growing PPV-infected plums and blackt horns can be considered equally important source of sharka infection as PPV -susceptible cultivars of plums, apricots and peaches. High PPV concentrati on in flowers is of diagnostical value. High variability of relative PPV co ncentration was observed inside the species among individual cultivars. Sus ceptible cultivars were characteristic by high relative PPV concentration, e.g. apricot cvs. Vegama (9.8 x 10(-5)) and Velkopavlovicka (1.95 x 10-4), and peach cvs. Maria Emilia (7.81 x 10(-4)) and Harbinger(1.56 x 10(-3)). O n the other hand, cultivars resistant to PPV were characteristic by very lo w relative PPV concentration, e.g. apricot cv. Stark Early Orange (5 x 10(- 2)) and peach cvs. Envoy (5 x 10(-2)) and Favorita Morettini (2.5 x 10(-2)) . The highest relative PPV concentration was found in young trees newly inf ected with PPV.