Introduction
Phytophthora heveae
A. W.
Thompson (1929)
Phytophthora heveae
was first described by Thompson in 1929 as the cause of black
stripe disease on Hevea (rubber)
plantations in
Cultural Characteristics
The minimum temperature for growth is 11.5°C, the optimum temperature for growth is 25°C, and the maximum temperature for growth is 31.0–32.5°C (Fig. 2). P. heveae does not produce aerial mycelium.
Reproductive Structures
Asexual Structures
Sporangiophores:
Sporangiophore branching is irregular and the sympodium is simple. Intercalary swellings are often present.
Sporangia:
Sporangia are papillate with a conspicuous apical thickening (5 µm in diameter) (Fig. 3). Sporangia are irregularly shaped, obpyriform to ellipsoidal, and often asymmetrical and form lateral stalks. The base is rounded. They are 20–49 × 27–66 µm (average 29.6 × 45 µm). The length–breadth ratio is 1.1:1–2.9:1. Sporangia are caducous with a medium pedicel length of less than 10 µm. Caducity is not always noted in the early reports.
Chlamydospores:
Chlamydospores are not produced.
Hyphae:
Hyphal swellings are small to large and resemble abortive reproductive organs.
Sexual Structures
P. heveae is homothallic.
Antheridia:
Antheridia are amphigynous and usually spherical but sometimes bicellular or cylindrical (10 × 11 µm).
Oogonia:
Smooth-walled oogonia form readily in culture in close groups or clusters and are globose. They are 17–32 µm in diameter (average 22.3 µm) and have a tapered or broadly funnel-shaped oogonial stalk. The oogonial wall is smooth.
Oospores:
Oospores are round, smooth, thick walled, 15–26.8 µm in diameter (average
21.5
µm), and markedly
aplerotic (Figs. 3 and 4).
Host Range and Distribution
Host |
Common Name |
Disease |
Geographical Distribution |
Agathis australis |
Kauri |
Root rot |
|
Bertholletia excelsa |
Brazil nut |
Leaf blight (Fig. 5) |
|
Cocos nucifera |
Coconut |
Bud rot; nut fall |
|
Eucalyptus pilularis |
Blackbutt |
Trunk canker |
|
Hevea brasiliensis |
|
Black stripe |
|
Mangifera indica |
Mango |
Leaf blight |
|
Persea |
Avocado |
Trunk canker |
|
Pinus patula |
Mexican yellow pine |
Root rot |
|
Psidium guajava |
Apple guava |
Leaf blight |
|
Rhododendron sp |
Rhododendron |
Dieback; wilt |
|
Theobroma cacao |
|
Pod rot |
|
Symptoms
The pathogen has been reported on rubber, cacao, avocado, mango, guava,
rhododendron, Brazil nut (Fig. 5), eucalyptus, and pine.
Black Stripe
of Hevea:
The symptoms are similar to those caused by
P. palmivora or
P. meadii on Hevea
spp. (Orellana, 1959). The pathogen causes a
sunken discolored lesion on the bark above the tap area.
Vertical fissures in the bark can occur, and when it is stripped away, a black
line can be seen. Oospores form in the tissue in contrast to
P. meadii and P palmivora.
P. heveae causes watery green patches, covered with
mycelium, on pods (Erwin and Ribeiro, 1996).
Pod Rot of
Cacao:
The pathogen infects the pods and causes a light brown lesion.
This lesion is lighter in color than the lesion caused by
P. palmivora on cocoa pods. Oospores form abundantly, but few sporangia are
produced (Waterhouse, 1974).
Trunk Canker
of Avocado:
Cracked and bleeding cankers form on the lower levels of the trunk and on the
upper rootstock of avocado trees. Diseased trees are stunted and the foliage
turns light green. Dieback sometimes occurs when the pathogen spreads, and the trees
eventually die.
References
Cline, E. T., Farr,
D. F., and Rossman, A. Y. 2008. A synopsis of Phytophthora with accurate scientific names, host range, and
geographic distribution. Plant Health Progress doi:10.1094/PHP-2008-0318-01-RS.
Erwin, D. C., and Ribeiro, O. K.
1996.
Phytophthora Diseases Worldwide. American Phytopathological Society,
Orellana, R. G. 1959. Variation in
Phytophthora palmivora isolated from cacao and rubber.
Phytopathology 49:210-213.
Stamps, D. J. 1978. Phytophthora heveae.
CMI Descr. Pathog. Fungi Bact. 594:1-2.
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
Thompson, A. W. 1929. Phytophthora
species in
Waterhouse, G. M. 1963. Key to the species of
Phytophthora de Bary. Mycol. Pap. 92.
CAB International, Wallingford, United Kingdom; Commonwealth
Mycological Institute, Kew
Waterhouse, G. M. 1974. Other
Phytophthora species recorded on cacao. Pages 71-79 in: Phytophthora Disease
of Cacao. P. H. Gregory, ed. Longman,