In eukaryotic cells, a family of serine/threonine protein kinases known as mitogen-activated protein kinases (MAPKs) are involved in diverse signal transduction pathways, including biotic and abiotic stress responses (Sinha et al., 2011). The MAPK of P. sojae was significantly up-regulated from 6 h after treatment (10% and 0% in treatment and control, respectively). In fungi, MAPKs are important to maintenance of cell wall integrity, hyper-osmoregulation and spore formation. Up-regulation of P. sojae MAPK was found to be required for formation of zoospores and cysts in a stress-mediated manner ( Li et al., 2010). To overcome the stress caused by the extract, P. sojae might strengthen its cell wall or shorten its life cycle through the formation of spores via up-regulation of MAPK. However, we did not detect increased sporulation during treatment.