Susceptibility of Wheat Varieties to Soil-Borne <i>Rhizoctonia</i> Infection

Abstract

Response of 19 wheat varieties cultivated in Hungary varied within large limits to soil borne Rhizoctonia infection. The most frequent symptom, usually leading to d a mping off was the root neck necrosis. Four significant factors influencing the susceptibility of wheat comprised 71% of total variation but none of them was dominant. The inhibition of devel opment of survivors in Rhizoctonia infested soil correlated with overall susceptibility of variety concerned. The varie ties Emese, Kikelet and Palotás are proved to be less susceptible, but none of the varieties could be certified as tolerant. No relationships were revealed between pathogenicity of 26 Rhizoctonia strains studied and their taxonomic position or origin. The anamorph strains of Athelia , Ceratobasidium , Ceratorhiza and Waitea similar to Thanatephorus ana morphs selectively infected the wheat varieties, but the syndromatic pictures were undistinguishable with unarmed eye. R . solani was proved to be more aggressive against germinating wheat than R . cerealis . Nine significant factors influ encing the virulence of Rhizoctonia strains comprised 82% of total variation, and six of them influenced exclusively Thanatephorus anamorphs.