TOWARDS RINGSPOT AND VARIEGATION IN MOUNTAIN ASH LEAVES

Ringspot and variegation are very common in leaves of mountain ash tre es. To elucidate the problem of causal agents of that disease in the C zech territory, leaves, flowers and fruits of trees sampled at three h abitats in surroundings of Prague were indexed by ELISA for infection with apple chlorotic leaf spot (ACLSV), apple mosaic (ApMV) and cherry leaf roll (CLRV) viruses. Out of 29 investigated trees, three were fo und to be infected with ACLSV, five with ApMV while 17 trees exhibited infection with both viruses. All trees were CLRV negative. There was no correlation between type of symptoms, their intensity and infection with a particular virus or mixed infections. Possible role of mountai n ash trees as spontaneous sources of ACLSV and ApMV infection is disc ussed.