Key words: Rhizoctonia solani Kuhn., biological characterization, hypovirulence,
mycovirus
by: Supyani and Hardjono Sri Gutomo
A filamentous fungus Rhizoctonia solani Kuhn. is the important pathogen of many diseases on crops. To date, there is no efficiently control method to the disease. So, the biological control method is a tactful choice. In the field, there are some hypovirulent strains within a species of fungus. The hypovirulent phenomenon could be caused by virues (mycoviruses) infection. From phytopathological perspective, these mycoviruses could be developed as biocontrol agents. Recently was developed Rhizoctonia solani virus 717, a virus that was isolated from a hypovirulent strain of R. solani, to control the fungus. In Indonesia, the development of mycovirus as biocontrol agents is not conducted yet. This research was aimed to get mycovirus from hypovirulent isolates of R. solani collected from the field, as a preliminary study toward development of the virus as biocontrol agents. We have collected 400 isolates of R. solani from the field. Morfological characterization and virulence tests revealed that the collected isolates perform varied colony phenotype and virulence. Finally, we identified 5 hypovirulent isolates i.e. isolate 11, 13, 15, 19, and 12 which perform relatively slower in colony growth and weaker in virulence compared to the virulent isolate. The 5 hypovirulent isolates were also indicated viruses infected.