Buletin USAMV-CN, 63/2006 (-) ISSN 1454-2382 FIRST DETECTION AND MOLECULAR CARACTERIZATION OF PLUM POX VIRUS RECOMBINANT STRAIN IN ROMANIA Zagrai I. 1 , Ioana Gaboreanu 2 , Beatrix Ferencz 3 , Luminita Zagrai 1 , D. Pamfil 2 , O. Popescu 3 , M. Ravelonandro 4 , Nieves Capote 5 , Katalin Kovacs 2 1 Fruit Research and Development Station Bistrita, 3, Drumul Dumitrei Nou street, 420127, Bistrita, Romania, e-mail: izagrai@yahoo.com 2 University of Agricultural Science and Veterinary Medicine Cluj-Napoca, Romania 3 Babes Bolyai University, Faculty of Biology and Geology, Cluj-Napoca, Romania 4 Institute Nationale de la Recherches Agronomique Bordeaux, France 5 Instituto Valenciano de Investigaciones Agrarias, Valencia, Spain Key words: Romania, Plum pox virus, serological and molecular variability, virus strains, PPV-Rec. Abstract. Plum pox virus (PPV) is the most dangerous viral pathogen of stone fruits causing serious yield losses. Although PPV is widespread in Romanian plum orchards, very limited information about the variability of isolates is known. In this study we collected and investigated twenty PPV isolates from two experimental plots from Fruit Research and Development Station Bistrita. PPV strains were serologically determined by TAS- ELISA using PPV-D and PPV-M specific monoclonal antibodies. Molecular strain typing was performed by IC- RT-PCR targeting three genomic regions (Cter)CP, (Cter)NIb - (Nter)CP and CI. RFLP analysis was used to distinguish the two major strains, D and M based on a Rsa I polymorphism located in (Cter) CP. PCR products spanning (Cter)CP and (Cter)NIb - (Nter)CP regions were sequenced. All PPV isolates typed as PPV-M by serological analysis and also by molecular differentiation in (Cter)CP region proved to be recombinants between PPV-D and PPV-M when the molecular analysis were performed in (Cter) NIb – (Nter)CP region. The sequencing results revealed a high homology with different sequences of PPV recombinant (PPV-Rec) previously reported. All these recombinant isolates share the same recombination breakpoint and have conserved the DAG motif, which is considered essential for potyvirus aphid transmission. This genetic similarity confirms that PPV-Rec may represent an ancestral group with a common evolutionary origin. This is the first report of naturally infected plum trees with recombinant PPV strain (PPV-Rec) in Romania and predicted a widespread in the other areas where plum is growing. INTRODUCTION Plum pox virus (PPV) or Sharka is considered one of the most devastating diseases of stone fruits. The virus is very detrimental because it reduces the quality of fruits and causes premature dropping (Dunez and Sutic, 1988, Nemeth, 1994). Therefore, PPV is considered one of the significant limiting factors for a profitable plum growing (Stoev et. al., 2004). Sharka is originated from Eastern Europe and was described for the first time around 1915 in Bulgaria (Atanasoff, 1932). Since then, the disease has progressively spread to a large part of the European continent, around the Mediterranean basin and near and Middle East. Also, it has been found in India and America (Chile, USA, Canada). In Romania, Sharka is spread in all plum growing areas causing serious yield losses especially on sensitive cultivars (Minoiu, 1997, Zagrai et al, 2001). Despite this economic importance, the information about the occurrence and spread of different PPV strains in Romania are extremely limited. The virus strains identification is a basic condition in effective management and/or control of virus spreading (James and Varga, 2004). For breeding programmes and