Investigations on black root rot disease of mulberry caused by Lasiodiplodia theobromae

Mulberry is an important food plant for domesticated silkworm (Bombyx mori L.). Among several root rot diseases reported in mulberry, black root rot caused by Lasiodiplodia theobromae has now emerged as a major disease. The survey was conducted and black root rot incidence was found to be maximum (51.7%) in Coimbatore district and minimum (14.1%) in Erode district. On PDA, L. theobromae covered Petri plate within three days with cottony white fluffy and slowly turned to black colour. All the four isolates were identified by molecular characterisation through PCR with ITS region and sequences were deposited in NCBI database. Among biocontrol agents screened, Trichoderma asperellum TRI 15 and T. virens TRI 37 were found to be inhibitory with 67.7% and 66.6% reduction in mycelial growth. Five mulberry varieties were screened, variety G2 showed resistance and V1 was highly susceptible.