Leaf Spot and Blight of Peony caused by Phytophthora cactorum

Kim, B. S.; Lim, Y. S.; Kim, J. H.

doi:2003.19.6.291

Plant Pathol J > Volume 19(6); 2003 > Article

The Plant Pathology Journal 2003;19(6):291-293.
DOI: https://doi.org/10.5423/PPJ.2003.19.6.291 Published online December 31, 2003.

Leaf Spot and Blight of Peony caused by Phytophthora cactorum

B. S. Kim, Y. S. Lim, J. H. Kim

Abstract

Leaf spot and blight disease of tree peony (Paeonia suffruticosa Andr.) was found in an apartment garden in Daegu in May 2003 for the first time in Korea. The causal organism was identified as Phytophthora cactorum (Leb. And Cohn) Schroeter. The causal fungus was homothallic, and produced distinctively papillate, ovoid to subspherical, and caducous sporangia with pedicel. Sporangia that formed in water measured 23.4-42.9×21.5-35.1 μm in range with an average of 35.3±4.6×26.9±3.6.0 μm, l/b ratio=1.31, papillae approximately 3.7 μm high, and pedicels 2.8 μm long. Oogonia were spherical and 21.5-37.1 μm in diameter with an average of 29.6±4.9 μm. Oospores were spherical, mostly plerotic, and light orange brown when mature, and measured 19.5-31.2 μm in diameter with an average of 25.2±4.4 μm. Antheridia were almost ovoid or clubshaped and 11.7-15.6×9.8-11.7 μm in size.

Key Words: Paeonia suffruticosa, Phytophthora catorum, taxonomy, Landscape plant