Heat-Stable Factor that Promotes Magnaporthe grisea Infection to Rice Plants in the Supernatant of Conidia Suspension

Abstract

In the rice-Magnaporthe grisea interaction, the presence of the factors that the pathogen produces to enhance their infection had been discussed long time but has not come to definite conclusion yet. We found the infection-promoting activity in the supernatant of conidia suspension of M. grisea (SCS). Addition of SCS promoted the extension of infectious hyphae into the excised leaf sheath of rice compared to water. The activity was found in the SCS from five virulent and three avirulent strains of M. grisea on Nipponbare (Pia), and the effect was much more evident in compatible than incompatible interaction. The infection of non-rice isolates of M. grisea to rice plants was not affected by SCS. Boiled SCS retained the activity, indicating that the factor is heat-stable. The factor was soluble in methanol but not in ethyl acetate. Some chemical and biological characterization of the factor will be reported.