IDENTIFICATION AND COMPARISON OF DIFFERENT STRAINS OF APPLE CHLOROTIC LEAF SPOT VIRUS AND POSSIBILITIES OF CROSS PROTECTION
This paper reports the results obtained from the comparison between strains of CLSV from apple and Prunus. These comparisons were made by noting the symptoms on a wide range of woody and herbaceous indicators, and by the serological technique.
Possibilities of interactions between four purified strains of CLSV were evaluated on two indicators, and the results were recorded with regard to the appearance of line pattern on Malusplatyca rpa and bark split on Prunus domestica P 707.
Results greatly depended on the host plant and the nature of the strains. On Malusplatyca, no cross protection was observed, and line pattern symptoms did develop whatever the strain combination was. On the contrary, inoculation of P. domestica P 707 with a mild strain (unable to induce bark split symptoms) always prevented the plant from developping symptoms when surinfected with a strain normally inducing severe bark split.
Our recent results show a new case of cross protection and they also point out, once again, the great diversity of the virus strains and their economical importance.Routine testing for plum pox virus confirmed a great similarity between plum pox symptoms and those associated on a few plum cvs. with some CLSV strains. But, if this economical importance is partly due to the severity of symptoms it also results from the high level of infection in several Prunus sp.