Phytophthora lateralis discovered in an old growth Chamaecyparis forest in Taiwan

Abstract

The geographic origins of the invasive Phytophthora species, P. lateralis and P. ramorum are unknown. In 2008 soil samples were collected in an old growth yellow cedar (Chamaecyparis obtusa var. formosana) stand in the Ma‐kau Ecological Park in north eastern Taiwan and subjected to Phytophthora baiting procedures at 18°C. Cedar needle baits yielded isolates of a slow growing Phytophthora culture from one soil sample, together with P. cinnamomi. Phytophthora bisheria sp. nov. was obtained from another sample. The slow growing isolates conformed closely to P. lateralis in the morphology of their sporangia and chlamydospores, growth–temperature relationships, absence of gametangia and their ITS and cox II sequences. The isolates’ sporangia were partially caducous, with short pre‐formed pedicels of ca. 3–5 μm, a highly unusual feature in a non‐papillate Phytophthora. The isolates also produced multicellular stromata on cedar decoction agar. Small morphological and molecular differences were observed between the Taiwan‐isolates and Oregon‐control isolates. Taiwan may lie within the geographic centre of origin of P. lateralis. By analogy Japan may also lie within the natural range of P. lateralis; and Japan, along with Taiwan and Yunnan, could be an origin for the closely related P. ramorum.