New Records of Phytophthora Diseases of Aromatic Crops in Taiwan

Abstract

Four species of Phytophthora isolated form aromatic herbs grown in the fields during 2001-2009 were proven to be the new records of pathogens on these crops in Taiwan. They were P. parasitica (=P. nicotianae) on blue salvia (Salvia farinacea) and pepper tree (Zanthoxylum piperitum), P. palmivora and P. tropicalis on rosemary (Rosmarinus officinalis), and P. citrophthora on rose geranium (Pelargonium graveolens). Phytophthora parasitica attacked the root system of pepper tree, resulting in yellowing and death of diseased plants. Blue salvia was highly susceptible to infection by P. parasitica in Taiwan in rainy season. Infected plants showed blight symptoms on leaves, stems and flowers and died eventually. All the P. parasitica isolates from diseased plants of pepper tree and blue salvia belonged to A^1 mating type. Phytophthora palmivora and P. tropicalis were the pathogens of rosemary, causing leaf and stem blights. All the isolates of these two species belonged to A^1 mating type. Phytophthora citrophthora was the causal agent of rose geranium, showing severe blight symptoms on leaves and stems. All the isolates of P. citrophthora from diseased plants of rose geranium belonged to A^1 mating type. Molecular data of the internal transcribed spacers (ITS) region and the partial β-tubulin gene also support the traditional classification based on morphological characteristics of P. parasitica, P. palmivora and P. tropicalis. However, these molecular information can not differentiate P. citrophthora from the other three species of Phytophthora including P. botryose, P. meadii and P. colocasiae. 自2001年至2009年調查台灣的香草（芳香）作物疫病，發現有5種未曾正式報告之疫病新紀錄，包括Phytophthora parasitica(=P. nicotianae)危害胡椒木(Zanthoxylum piperitum)與粉萼鼠尾草(Salvia farinacea)；P. palmivora與P. tropicalis危害迷迭香(Rosmarinus officinalis)；及P. citrophthora危害香葉天竺葵（防蚊草，Pelargonium graveolens）。P. parasitica感染胡椒木的主根與系根，造成根系壞疽、腐敗及稀少，導致植株生長緩慢、葉片黃化、枝枯，嚴重時全株枯萎死亡；所有分離到菌株均爲A^1配對型。危害鼠尾草的疫病菌也均爲P. parasitica，且爲A^1配對型，庭園與花圃鼠尾草較易發病，多在降雨季節；罹病株的葉片、莖部及花器枯萎，終至全株死亡。疫病菌感染迷迭香的葉片與莖部，常造成整枝莖部的葉片褐變與枯萎，分離到的疫病菌有兩種，P. palmivora與P. tropicalis，均爲A^1配對型，其中以P. palmivora的分離率較高；兩種疫病菌在人工接種後造成的病徵相同，無法區分。A^1配對型的P. citrophthora自香葉天竺葵的腐敗莖部組織分離得到，罹病部位以上枝條與葉片枯萎。這些寄主植物在接種個別分離得到的疫病菌游走子懸浮液後，都出現與田間自然發病時相同的病徵，而且相同的疫病菌亦均自發病組織回分得到。這些在台灣的新病害中，除P. parasitica危害鼠尾草屬(Salvia sp.)外，其餘P. parasitica危害胡椒木、P. palmivora與P. tropicalis危害迷迭香、及P. citrophthora危害香葉天竺葵在世界其他各地尚未發表過。