Figure 1. Morphology of Phytophthora katsurae. Upper row, Papillate sporangia. Lower row, Oogonium with verrucose (bullate) wall and an amphigynous antheridium; and papillate sporangia, one of which is bipapillate. (Courtesy A. Vaziri; Reproduced from Erwin and Ribeiro, 1996)

 

Figure 2. Culture of Phytophthora katsurae grown on V-8 juice agar. (Courtesy Jean B. Ristaino)

 

Figure 3. Sporangia of Phytophthora katsurae (×1,000). (Courtesy Jean B. Ristaino)

 

Figure 4. Ornamented oogonium of Phytophthora katsurae with tapered base, amphigynous antheridium, and oospore. (Courtesy Janice Y. Uchida; Reproduced from Elliott et al., 2004)

 

Figure 5. Death of young coconut fronds is the first common symptom of Phytophthora katsurae infection. (Courtesy Janice Y. Uchida; Reproduced from Phytophthora katsurae. Crop Knowledge Master. Extension Entomology and UH-CTAHR IPM Program, University of Hawaii-Manoa)

 

Figure 6. Inoculations of healthy green fruits show that the initial fruit rot symptoms of Phytophthora katsurae infection are irregular, dark green, water-soaked areas. (Courtesy Janice Y. Uchida; Reproduced from Phytophthora katsurae. Crop Knowledge Master. Extension Entomology and UH-CTAHR IPM Program, University of Hawaii-Manoa)

 

Figure 7. Death of the spear leaf of a young coconut tree infected with Phytophthora katsurae. (Courtesy Jeri J. Ooka; Reproduced from Elliott et al., 2004)

 

Figure 8. Close-up of bud (heart) rot of coconut, caused by Phytophthora katsurae. (Courtesy Jeri J. Ooka; Reproduced from Elliott et al., 2004)

 

Introduction

Phytophthora katsurae  W. H. Ko & H. S. Chang (1979)

 

Phytophthora castaneae Katsura & Uchida (1976) (Katsura, 1976), a synonym for P. katsurae, was isolated from diseased chestnuts (Castanea crenata) in Japan and has been found in forest soils. Phytophthora katsurae was named by Ko and Chang (1979) as a replacement name for P. castaneae (L. Mangin) Clements & Shear (1931) and for P. castaneae Katsura & Uchida (1976), which are both considered illegitimate names. P. katsurae also infects coconut palm (Uchida et al., 1992). P. katsurae differs from P. cambivora, which is also a pathogen of chestnut, in that it is homothallic and its oospores are smaller than those of P. cambivora. P. katsurae is in Waterhouse’s group II species (Waterhouse, 1963) and has been described in more detail by Stamps (1985) (Fig. 1).

Cultural Characteristics

The minimum temperature for growth is 9°C, the optimum temperature for growth is 27°C, and the maximum temperature for growth is 32°C (Fig. 2).

Reproductive Structures

Asexual Structures

 

Sporangiophores:

Sporangiophores do not branch. Sporangia are sometimes in a tight sympodium.

 

Sporangia:

Sporangia are mostly terminal, although they sometimes form laterally or intercalarily. Sporangia are limoniform, ovoid, obpyriform to obturbinate, and papillate, sometimes with multiple papillae. Sporangia are 10–37.5 × 10–42.5 µm (average 22.5 × 27.5 µm) (Fig. 3).

 

Chlamydospores:

Chlamydospores are 12–19.2 µm in diameter and spherical.

 

 

Sexual Structures

 

P. katsurae is homothallic.

 

Antheridia:

Antheridia are amphigynous and spherical to ovoid.

 

Oogonia:

Oogonia are 19–31 µm in diameter. Oogonia have warty or bullate protuberances on the surface and a distinct funnel-shaped base.

 

Oospores:

Oospores are 15–27.5 µm in diameter (average 20 µm) (Fig. 4). Oospores are markedly aplerotic.

Host Range and Distribution

Host

Common Name

Disease

Geographical Distribution

Castanea crenata

Chestnut

Trunk rot

Japan, Taiwan, Hawaii, Ivory Coast, Australia, Papua New Guinea

Cocos nucifera

Coconut

Fruit and heart rot

Japan, Taiwan, Hawaii, Ivory Coast, Australia, Papua New Guinea

Theobroma cacao

Cocoa

Pod rot

Ivory Coast

Symptoms

Trunk Rot of Chestnut:

Lesions develop 10–100 cm aboveground. The bark around the infected area begins to soften and fissures develop around the lesions. These fissures are covered with a black exudate that has a fermentation odor. Bark quickly dies. The infected tree normally dies within 4 years of infection (Erwin and Ribeiro 1996).

 

Fruit Rot of Coconut:

The disease develops and spreads after periods of heavy, prolonged rainfall. Fruit rot of coconut starts at the stem and affects fruit of all ages (Uchida et al., 1992) (Figs. 5–8).

References

Clements, F. E., and Shear, C. L. 1931. The Genera of Fungi. H. W. Wilson Co., New York.

 

Elliott, M. L., Broschat, T. K., Uchida, J. Y., and Simone, G. W., eds. 2004. Compendium of Ornamental Palm Diseases and Disorders. American Phytopathological Society, St. Paul, MN.

 

Erwin, D. C., and Ribeiro, O. K. 1996. Phytophthora Diseases Worldwide. American Phytopathological Society, St. Paul, MN.

 

Katsura, K. 1976. Two new species of Phytophthora causing damping-off of cucumber and trunk rot of chestnut. Trans. Mycol. Soc. Jpn. 17:238-242. (In Japanese)

 

Ko, W. H., and Chang, H. S. 1979. Phytophthora katsurae, a new name for P. castaneae. Mycologia 71:840-844.

 

Stamps, D. J. 1985. Phytophthora katsurae. CMI Descr. Pathog. Fungi Bact. 837.

 

Uchida, J. Y., Aragaki, M., Ooka, J. J., and Nagata, N. M. 1992. Phytophthora fruit and heart rots of coconut in Hawaii. Plant Dis. 76:925-927.

 

Waterhouse, G. M. 1963. Key to the species of Phytophthora de Bary. Mycol. Pap. 92. CAB International, Wallingford, United Kingdom; Commonwealth Mycological Institute, Kew, Surrey, England.