Some aspects of induced resistance to rice blast fungus, Magnaporthe grisea, in rice plant infested by white-backed planthopper, Sogatella furcifera

The effect of previous rice plant infestation of the white-backed planthopper, Sogatella furcifera, on the incidence of rice blast disease caused by the fungal pathogen, Magnaporthe grisea, was investigated. The fungal pathogen M. grisea was less likely to cause symptoms of leaf blast on rice plants that had been previously infested with S. furcifera than on uninfested plants. This indicates that resistance to M. grisea was induced in rice plants by infestation of S. furcifera. The number of blast lesions per plant decreased with increasing numbers of infesting S. furcifera from 0 to 10 pairs. The active period of induced resistance was maintained for a relatively long time being greater than 15 d. The difference in the incidence of leaf blast between S. furcifera infested and uninfested plants in the booting stage became smaller than that in the tillering stage, although there was a still significant difference in blast incidence between both infested and uninfested plants in booting stage. There was no significant difference in the incidence of leaf blast between damaged plants treated with needling and untreated control plants. This suggests that the simple mechanical effect to the plants caused by stylet insertion (penetration) and subsequent probing with the feeding behavior of S. furcifera. was not related to the observed phenomenon. In S. furcifera infested plants, the expression of two genes regarding beta-1,3-glucanase, Gns4 and Gns5, was confirmed by RT-PCR analysis. These results show that infestation of S. furcifera apparently induced physiological changes including gene expression that were related to pathogen resistance to M. grisea in rice plants.