is an important plant pathogenic fungus of many crops. Our previous study identified the agglutinin (SSA) that can be partially degraded by the serine protease CmSp1 from the mycoparasite . However, the biological functions of SSA in the pathogenicity of and in its response to infection by as well as to environmental stresses, remain unknown. In this study, SSA disruption and complementary mutants were generated for characterization of its biological functions. Both the wild-type (WT) of and the mutants were compared for growth and sclerotial formation on potato dextrose agar (PDA) and autoclaved carrot slices (ACS), for pathogenicity on oilseed rape, as well as for susceptibility to chemical stresses (NaCl, KCl, CaCl, sorbitol, mannitol, sucrose, sodium dodecyl sulfate, HO) and to the mycoparasitism of . The disruption mutants (Δ-175, Δ-178, Δ-225) did not differ from the WT and the complementary mutant Δ-178C in mycelial growth. However, compared to the WT and Δ-178C, the disruption mutants formed immature sclerotia on PDA, and produced less but larger sclerotia on ACS; they became less sensitive to the eight investigated chemical stresses, but more aggressive in infecting leaves of oilseed rape, and more susceptible to mycoparasitism by These results suggest that SSA positively regulates sclerotial development and resistance to mycoparasitism, but negatively regulates pathogenicity and resistance to chemical stresses.