Journal of Taiwan Agricultural Research

Author:Pao-Jen Ann*, Jyh-Nong Tsai, and Ien-Tien Wang

Abstract:

    Serious Phytophthora diseases of Cedrela sinensis and Zanthoxylum ailanthoides were found in the felds in Taiwan during the investigation of diseases of medicinal herb plants from 2006 to 2012. Diseased plants of C. sinensis showed symptoms of browning on basal stems which were shrunken within a few days, and the plants were droopy. Severely infected plants were leaf yellowing, stunted and killed due to root rotting. Diseased plants of Z. ailanthoides showed symptoms of water-soaked lesions on leaves, buds and stems, which enlarged in size and turned dark brown quickly. Eventually, the infected leaves turned yellow and fell prema-turely, and the buds and stems rotted and collapsed. Diseased plants also showed symptoms of basal stem rot and root rot. Two species of Phytophthora, including P. nicotianae (P. parasiti-ca) (2 A1 isolates) and P. palmivora (3 A2 isolates) were isolated from C. sinensis and one spe-cies of Phytophthora (P. nicotianae, 7 A1 and 4 A2 isolates) was isolated from Z. ailanthoides. Results of pathogenicity tests by artifcial inoculations showed that both P. nicotianae and P. palmivora were the pathogens of C. sinensis and P. nicotianae was the pathogen of Z. ailanthoides, with disease symptoms identical to the diseased plants observed in the felds. Each Phytophthora isolate was re-isolated from the infected tissues of the inoculated plants. All the isolates of Phytophthora obtained from C. sinensis and Z. ailanthoides belonged to the typical types of P. nicotianae or P. palmivora. The range of temperature for mycelial growth of P. nicotianae isolates were 8–36℃ with optimal temperature at 28℃, while the range for P. palmivora was 12–35℃ with optimal temperature at 28℃. Sporangia of P. nicotianae isolates were spherical or sub-spherical, unsymmetrical, with semi-spherical papilla, and non-deciduous, whereas sporangia of P. palmivora were spherical, ovoid or elliptical, symmetrical, with semi-spherical papilla, and deciduous with very short pedicels (< 5 μm). Both Phytophthora species produced chlamydospores on agar media. DNA sequences of the internal transcribed spacers (ITS1-5.8S rDNA-ITS2) region and the partial β-tubulin gene also support the morphological classifcation of P. nicotianae and P. palmivora. This is the frst record of Phytophthora diseases of C. sinensis caused by P. nicotianae and P. palmivora and Z. ailanthoides caused by P. nicotianae in Taiwan and in the world.

Key words:Cedrela sinensis, Zanthoxylum ailanthoides, Phytophthora diseases, Phytophthora nicotianae, Phytophthora palmivora

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