Cherry chlorotic rusty spot and cherry leaf scorch: two similar diseases associated with mycoviruses and double stranded RNAs

Cherry chlorotic rusty spot (CCRS) is a disease of unknown etiology affecting sweet and sour cherry in Southern Italy. CCRS has constantly been associated with the presence of an unidentified fungus, double-stranded RNAs (dsRNAs) from mycoviruses of the genera Chrysovirus, Partitivirus and Totivirus and two small circular RNAs (cscRNAs) that may be satellite RNAs of one of the mycoviruses. The similarity of CCRS and Cherry leaf scorch (CLS), a disease caused by the perithecial ascomycete Apiognomonia erythrostoma, is discussed in the light of symptomatology, fungal fructifications, nucleotide sequence analysis of fungal genes, including the 18S rDNA amplified by PCR from infected leaves, and isolated mycelia. Comparison of mycoviral dsRNAs isolated from plants affected by both diseases further supports the view that CCRS and CLS are closely related. This is the first report showing the presence of CCRSlike mycoviral dsRNAs in CLS-infected cherry trees from Spain, indicating that CCRS-associated mycoviruses are more widely spread than though before.