U. virens secretes compounds including ustiloxins into media, and ustiloxins are toxic to humans and livestock. To verify the effects of secreted compounds on rice pollen development, we used the supernatant of old-cultured U. virens to treat rice pollen grains to investigate the ger-
mination rate. Rice pollen grains were first treated with germination solution (15% sucrose, 20 mg/L borate and 40 mg/L CaCl2), after treatment for 10 min, about 75% of pollen grains germinated (Figure 3(a)), whereas pollen grain germination was completely inhibited by the treatment of the supernatant (Figure 3(b)).