SYSTEMATICS AND TAXONOMY IN THE OOMYCETES Molecular Detection of Phytophthora tentaculata in Infected Aucklandia lappa Tissues and Soil on the Basis of Ypt1 Gene Distribution of RXLR effectors Avr3a, Avr4 and IPI-O in Phytophthora infestans isolates in China Nonhost Interaction of Phytophthora sojae and Arabidopsis thaliana and Genetic Analysis of a Susceptible Mutant