Apple viral diseases diagnosed in the germplasm collection at ICDP Maracineni Romania

General purpose of this study: the latent viruses elimination from the breeding process and the achievement of a VF stock used as initial base for the propagation process. The sanitary state control of the clonal accessions in the apple germplasm collection has in view the viruses elimination from the breeding process and the establishment of a virus and phytoplasma free plants stock, to be used as initial source (Prebasis) of grafting for propagation. From 1994, 19 long-term cultivar selections; 5 new native cultivars; 17 cultivars from international exchanges and 10 rootstock selections have been tested for latent viruses on woody indicators approved by O.E.P.P. (Malus Platycarpa, 'Spy 227', 'Lord Lambourne'. R 12740-7A', 'V. Crab'). The rootstock selection G(21) was also ELISA tested for ACLSV, ApMV and SGV. The results of the biological testing have made evident the presence of 1-2 latent viruses to 7 from 19 long-term cultivar selections (36,8%) and to a 5 from 10 rootstock selections (50%). Also, 7 from 17 foreign cultivars (41,2%) have been found infected with 1-4 latent viruses. Apple chlorotic leaf spot virus was found in 37,2% from the tested accessions; Spy epinasty and decline in 25,5%, Apple stem grooving and Apple stem pitting - 7, 8% and Apple mosaic virus was found only in 'Granny Smith' cv., and serological also in the rootstock selection G21, together with ACLSV. From the latent viruses that were tested, only ACLSV was found alone in 6 from 51 accessions. The other viruses have been found in complexes of 2-3 or 4 viruses, but in all the cases together with ACLSV. The results obtained for the rootstock selection G21 have leaded us to the conclusion that for the clones that we have thermo treated, only the biological retesting is not enough to decide their inclusion in the "virus free" category. The infected clones are replaced with virus free plants, and the healthy ones are available as "virus free" material simultaneously with their maintenance in the bio-depositary, as initial source for grafting propagation.