PRELIMINARY RESULTS OF THE STUDY ON THE SPREAD OF APPLE CHLOROTIC LEAF SPOT VIRUS (ACLSV) IN DIFFERENT FRUIT TREE SPECIES IN KYUSTENDIL REGION OF BULGARIA

The survey was carried out mostly in one of the main fruit tree growing regions of Bulgaria – Kyustendil, during the period of 2004-2005. A total of 632 trees corresponding to 50 apple, 27 pear, 19 plum, 4 peach, 9 sweet cherry and 4 sour cherry cultivars and 21 apricot elites were tested for the presence of Apple chlorotic leaf spot virus (ACLSV) and six other viruses by ELISA. Samples for analyses were collected from different organs of plants: flowers, leaves or phloem tissues. In the present research, ACLSV was not found in pear, plum, apricot and sour cherry. The highest infection rate of the virus among the infected fruit tree species was in apple (73 %) followed by sweet cherry (13.3 %) and peach (11.76 %). The frequency of mixed infection was 43.2 % in the infected apple, 33.4 % in sweet cherry and 12.5 % in peach trees. The highest concentrations of ACLSV, measured by ELISA, were observed in naturally grown flower petals of apple and sweet cherry trees in May.