377 Proc. 18 th Int. Symp. on Fruit Tree Virus Diseases Ed. M.F. Clark Acta Hort. 550, ISHS 2001 SURVEY FOR STONE FRUIT PHYTOPLASMAS IN THE CZECH REPUBLIC M. NavrÆtil, P. VÆlovÆ, Z. PoncarovÆ - VorÆčkovÆ R. FialovÆ and K. PetrovÆ Research Institute of Crop Faculty of Sciences Production Palack University Olomouc DrnovskÆ 507 lechtitelů 11 161 06 Praha 783 71 Olomouc-Holice Czech Republic Czech Republic J. FrÆnovÆ and J. NebesÆřovÆ R. KareovÆ Institute of Plant Molecular Biology Research and Breeding Institute of Academy of Sciences Pomology BraniovskÆ 31 Holovousy v Podkrkono 370 05 ČeskØ Budějovice 508 01 Hořice Czech Republic Czech Republic Keywords : Phytoplasma, Stone fruits, Occurrence, PCR, RFLP, Czech Republic Abstract Phytoplasmas were detected in apricots (Prunus armeniaca), peaches (Prunus persica), plums (Prunus domestica), plum hybrid (Prunus salicina x cerasifera), sweet cherries (Cerasus avium), sour cherries (Cerasus vulgaris), almond hybrid (Prunus amygdalus x persica) and Prunus cerasifera. A predominant phytoplasma associated with diseases of apricots, peaches and plums was identified as European stone fruit phytoplasma (= apricot chlorotic leaf roll phytoplasma). Sweet cherries and sour cherries were affected mainly by aster yellows (AY) phytoplasma. Furthermore, the obtained results can also provide the evidence of the presence of apple proliferation phytoplasma and pear decline phytoplasma (= peach yellow leaf roll phytoplasma) in inspected orchards within the Czech Republic. 1. Introduction Phytoplasmas are known to affect several Prunus species and are the important pathogens of stone fruits. There are several phytoplasma-induced diseases of stone fruit trees in Europe, for example apricot chlorotic leaf roll, plum leptonecrosis, plum decline and cherry MoliØre disease. Stone fruit trees infected with phytoplasmas can often show striking symptoms: chlorosis, discoloration, foliar deformities, proliferation, stunting, die-back of branches and roots. However, symptom expression may irregularly depend on environmental conditions, a seasonal variation in the phytoplasma colonisation of the tree and/or a possible interaction of phytoplasmas with some other pathogens. There are a few references concerning stone fruit phytoplasmas within the Czech Republic area. In the South Moravia region, a sporadic occurrence of apricot witches· broom disease was described by Blattn (1977). Since 1980s, symptoms of apricot chlorotic leaf roll disease have been observed on apricot trees (Ackermann, personal communication). Intensive observations of stone fruit phytoplasmas in the Czech Republic began in 1970s (NavrÆtil et al., 1998). This paper summarises the results of stone fruit tree phytoplasmas screened in the Czech Republic during the period 1993 - 1999.