Introduction
Phytophthora boehmeriae
Sawada (1927)
Phytophthora boehmeriae
was first isolated from the leaves of the Chinese silk tree
Boehmeria nivea by Sawada in
Cultural Characteristics
Colonies are uniform and compact with well-defined margins and dense aerial mycelia (Fig. 2). The minimum temperature for growth is 5–6°C, the optimum temperature for growth is 25°C, and the maximum temperature for growth is 32°C. Mycelium is gnarled and grows in a tortuous pattern.
Reproductive Structures
Asexual Structures
Sporangiophores:
Sporangiophores are sympodial.
Sporangia:
Sporangia are papillate and spherical, ovoid, ellipsoidal, obpyriform, or obturbinate. Mean sporangial measurements are 20–51 × 28–69 µm (Fig. 3). Sporangia are caducous with a short pedicel length of 5.0 µm or less (Stamps, 1978; Waterhouse, 1963). The average sporangia length–breadth ratio is 1.25–1.6.
Chlamydospores:
Chlamydospores are produced infrequently and are 26–52 µm (average 41 µm).
Sexual Structures
P. boehmeriae is homothallic and oospores form abundantly in host tissues.
Antheridia:
Antheridia are amphigynous, spherical, and 8–16 × 12.5–21 µm.
Oogonia:
Oogonia are smooth walled, hyaline to yellow, and 21.7–31.7 µm (average 28 µm). The oogonial stalk is not tapered.
Oospores:
Oospores form abundantly in host tissues with a diameter of 20.9–27.6 µm (average 25.1 µm) (Fig. 4).
Host Range and Distribution
Host |
Common Name |
Disease |
Geographical Distribution |
Acacia mearnsii |
Black wattle |
Gummosis |
|
Broussonetia papyrifera |
Paper mulberry |
|
|
Cedrus deodara |
Deodar cedar |
|
|
Citrus sinensis |
Sweet orange |
Brown rot |
|
Eucalyptus pilularis |
Eucalyptus, black butt |
Root rot |
|
Gossypium
spp. |
Cotton |
Boll blight |
|
Gossypium hirsutum |
Cotton |
Boll rot |
|
Pinus patula |
Mexican yellow pine |
Root rot |
|
Symptoms
Symptoms are similar to those described for brown rot of citrus caused by
P. citrophthora
(Erwin and Ribeiro, 1996). The pathogen is splash dispersed and infects
the fruit, causing a brown rot (Frezzi, 1941).
Diseased tissue is firm and leathery. It also causes a leaf blight
and root rot on a number of species and boll rot and blight on cotton.
The pathogen causes trunk lesions and gummosis on black wattle (Dos Santos et al., 2006)
(Fig. 5A and B).
References
Dos
Erwin, D. C., and Ribeiro, O. K. 1996. Phytophthora Diseases Worldwide. American Phytopathological Society, St. Paul, MN.
Frezzi, M. J. 1941. Phytophthora boehmeriae, the agent of brown rot of citrus fruits in the Argentine republic. Rev. Argent. Argon. 8:200-205.
Ho, H. H., and Chang, H. S. 1992. A re-evaluation of
Phytophthora
species described by K. Sawada in
Sawada, K. 1927. Descriptive catalog of the Formosan fungi III. Rep. Dep.
Agric. Gov. Res. Inst.
Stamps, D. J. 1978. Phytophthora boehmeriae. CMI Descr. Pathog. Fungi Bact. 591:1-2.
Stamps, D. J., Newhook, F. J., Waterhouse, G. M., and Hall, G. S. 1990.
Revised tabular key to the species of
Phytophthora
de Bary.
Mycol. Pap. 162.
CAB International, Wallingford, United Kingdom; Commonwealth Mycological
Institute, Kew,
Waterhouse, G. M.
1963. Key to the species of
Phytophthora
de Bary. Mycol. Pap. 92.
CAB
International, Wallingford, United Kingdom; Commonwealth Mycological
Institute, Kew,
Zheng, X. B., and Lu, J. Y. 1989. Studies on the
Phytophthora
species in