The chemical structure of a glycoprotein secreted from conidia of Mycosphaerella pinodes into the medium during germination was investigated, and its elicitor activity to induce pisatin synthesis in peas was examined. The glycoprotein showed a higher elicitor activity than the intra-conidial polysaccharide. The glycoprotein, whose molecular weight is about 130×10⁴, has ap partial structure in which a reducing terminal mannosyl residue of a trisaccharide ¹Man⁶-α←¹Man⁶β←¹Glu is Ο-glycosidically attached to serine in the protein portion.