Pathogenicity of Culture Filtrate Produced by Pyricularia oryzae Cav., the Causal Agent of Rice Blast

Abstract

Capability of culture filtrate peoduced by Pyricularia oryzae Cav. to incite blast symptom was conducted on rice variety KDML 105. Five isolates of the fungal pathogen were isolated from rice infected leaves. The result revealed that the symptoms produced by culture filtrate were quite similar to those produced by the fungal pathogen. The capabilities of culture filtrates for inciting disease symptoms were different among 5 isolates of the fungal pathogen. It might be concluded that culture filtrate containing toxic substance which was classified to pathotoxin could played an important role on virulent factor of blast pathogen. The response of rice leaves to culture filtrate was studied. The result indicated that as the increasing of culture filtrate concentrations, sizes and severity of lesions increased. The optimum incubation period for symptom appearance was 5 days after exposing culture filtrate to rice leaves. Rice varieties exhibited different responded to culture filtrate and their levels of response were determined by lesion sizes and lesion types.