Inheritance of infection cushion formation by rhizoctonia solani kühn on rice leaf sheath

Number of infection cushion formed by Rhizoctonia solani Kühn and the causal pathogen of rice sheath blight disease were observed to investigate the inheritance pattern of prepenetration activity of the fungus using four rice crosses. Tadukan and Tx765433, which are resistant and moderately resistant to sheath blight disease, respectively, have same dominant gene which controls infection cushion formation, but a moderately resistant variety Nortai has different dominant gene over Tadukan’s. F₁, F₂, and F₃ populations of two crosses between resistant and susceptible parents, Tadukan/Labelle and Tx765433/Labelle, revealed that infection cushion formation is governed by a single gene of host plants, and that the varietal ability to repress infection cushion formation on rice tissues is dominant over the inducement of infection cushion formation. It is apparent that wax deposits on rice leaf sheath surface are inhibitory to infection cushion formation in F₂ population of a cross, Tadukan/Labelle.