New records of Phytophthora diseases of Chinese medicinal herbs in Taiwan.
Three species of Phytophthora isolated from Chinese medicinal herbs grown in the fields during 2001-2009 were proven to be the new records of pathogens on these crops in Taiwan. They are Phytophthora cryptogea on dan-shen (Salvia miltiorrhiza), P. drechsleri on astragalus (huang-qi, Astragalus membranaceus) and P. nicotianae (=P. parasitica) on rehmannia (ti-huang, Rehmannia glutinosa). Phytophthora cryptogea attacked roots and basal stems of dan-shen, causing plant wilting, leaf drooping, and eventual plant death. Phytophthora drechsleri attacked leaves, stems and roots of astragalus, causing leaf and stem blight, and wilt and death of infected plants. Rehmannia was highly susceptible to P. nicotianae, as the infected plants were killed within a very short period of time. All the isolates of P. cryptogea, P. drechsleri and P. nicotianae obtained from the medicinal herbs in Taiwan belong to A1 mating types. Results of the inoculation tests in the greenhouse showed that all the three species were pathogenic and the disease symptoms on inoculated host plants were similar to the naturally infected plants grown in the fields. Molecular data of the internal transcribed spacers (ITS) region and a partial sequence of the β-tubulin gene also support the traditional classification based on morphological and physical characteristics of P. cryptogea, P. drechsleri and P. nicotianae. Phytophthora cryptogea on dan-shen and P. nicotianae on rehmannia have not been reported in any other country prior to this report.