Many mycoviruses may cause latent infection in their fungalhosts (Ghabrial and Suzuki, 2009). Some mycoviruses, how-ever, can produce serious phenotypic alterations in their fungalhosts, including hypovirulence and debilitation. This suggeststhat a few mycoviruses can be employed for biological con-trol of the fungal disease, as has been adequately proven withCryphonectria hypovirus 1 (CHV1), to control chest blight dis-ease in Europe (Nuss, 2005). Moreover, the coevolution of somemycoviruses with their hosts has contributed to the establish-ment of some host-mycovirus systems, which is beneficial for