SUSCEPTIBILITY OF GENOTYPES OF THE GENUS PRUNUS TO PLUM POX POTYVIRUS

Wild forms can become important as sources of resistance. Therefore, s everal genotypes of the genus Prunus were examined for their susceptib ility or resistance to plum pox potyvirus (PPV). For char purpose, the genotypes were grafted on PPV-diseased plum trees and their response was observed over three seasons. Re-indexing and resting were carried out biologically by double grafting with the PPV hypersensitive hybrid 'K 4' as well as by ELISA and IC-PCR 2 and 3 years p.i., respectively . P. americana, P. cerasifera x P. spinosa, P. insititia and P. spinos a rubrifolia showed a high susceptibility characterized by distinct sy mptoms and high virus concentrations. Distinct symptoms bur lower exti nction values in ELISA appeared in P. americana 'De Soto'. P. munsonia na x P. triflora showed no symptoms although a high virus concentratio n was established in the leaves. This species was assessed as PPV tole rant. P. nigra 'Mansan' also remained symptomless, showed low virus co ncentrations and nor fully systemic virus spread in the shoots. It was characterized as quantitatively resistant to PPV. Hypersensitivity wa s noticed in P. americana 'Hawkeye' and P. americana (wild form). P. c erasifera violacea and P. spinosa 'Schukina' also remained symptomless and no virus was detected by biological, serological and IC-PCR testi ng. Thus, these two species can be assessed as highly (qualitatively) resistant and immune, respectively. Possibly, they are suitable for us e as sources for PPV resistance.