Pathogenicity Differrentiation, Infection Process Of Rhizoctonia Zeae And Effect Of Temperature On Germs Infection

Rhizoctonia zeae Voorhees was an important pathogen of Maize sheath blight. The differentiation of pathogenicity, activities of cell wall degrading enzymes, infection process and effect of temperature on sclerotia germination and germs infection were studied. The results are as follows:23 strains of R.zeae and 1 strain of R.solani AG1- I A were inoculated to test the pathogenicity, using the leaf sheath inoculation method with pure culture of each strain in kernels. Lesion length and incubation period were measured. The results showed that all tested strains were pathogenic to maize. The incubation period of R.zeae isolates was 24-36 h and the range of lesion length was 9.38-17.25 cm.The lesion length on leaf sheath was considerable variation among the tested strains of R.zeae. These differences in lesion length suggested that the strains of R.zeae had differentia of pathogenicity. The pathogenicity of R.zeae was lower than R. solani AG1- I A (33.54 cm).Activities of cell wall degrading enzymes produced by R.zeae in vitro were studied. Results showed that R.zeae produced cellulose enzyme(Cx), polymethylgalacturonase (PMG) and polygalacturonase(PG). The activity of PMG was the highest. The production ability of CWDEs was evidently different among the isolates. There was a positive correlation between the production ability of Cx and the pathogenicity of the isolates. The activity of Cx markedly increased with increasing pathogenicity of the isolate. It indicated that the CWDEs of R.zeae played an important role in the infection.Infection process to maize sheath by R.zeae was studied. Results showed that R.zeae penetrated maize plants :; through the inner surfaces of leaf sheath. The pathogen penetrated...