Host reaction tests. Reactions of the
two isolates on different hosts were conducted
by mechanical inoculation. Inocula,
1:10 dilution (wt/vol), were prepared by
grinding leaves of infected mustard plants
in potassium phosphate buffer (50 mM, pH
7.5). At least 20 plants of each species
were inoculated and kept in an insect-proof
greenhouse for 1 month or longer for observation
of symptom development.