Introduction
Phytophthora syringae
(Berk.) Kleb. (1909)
Phytophthora syringae
was first isolated and described by Klebahn (1905; 1909) from diseased lilac trees,
Syringa vulgaris, in
Cultural Characteristics
The minimum temperature for growth is less than 5°C, and the maximum temperature
for growth is 23°C (Fig. 2). The optimum
temperature for growth is 15–20°C.
Reproductive Structures
Asexual Structures
Sporangiophores:
Sporangiophores form in a close monochasial sympodium with intercalary swellings.
Sporangia:
Sporangia are broadly ovoid or obpyriform, semipapillate, and noncaducous. Sporangia may have more than one apex and distortion and lateral attachment in some isolates (Gallegly and Hong, 2008). Sporangia form in succession from a single sporangium and average 36 × 57 µm (Figs. 3 and 4.11 and 4.12) (Waterhouse and Waterston, 1964). Size may vary depending on host and different dimensions can be found in Table 60.2 of Erwin and Ribeiro (1996).
Chlamydospores:
Waterhouse and Waterston (1964) and Ho and Jong (1993) did not report chlamydospore production, but Stamps et al. (1990) reported chlamydospores that were 25 µm in diameter.
Hyphae:
Hyphae can be up to 6 µm wide (Waterhouse and Waterston, 1964). Hyphal swellings are rounded, angular, often in chains, and occasionally delimited by septa. Hyphal coiling in old cultures is common (Fig. 1).
Sexual Structures
P. syringae is homothallic.
Antheridia:
Antheridia are predominately paragynous and occasionally amphigynous. Antheridia are 7 × 10 µm (Waterhouse and Waterston, 1964).
Oogonia:
Oogonia form abundantly in culture and host tissue and oogonium diameter averages 33 µm. Dimensions from different reports can be found in Table 60.2 of Erwin and Ribeiro (1996).
Oospores:
Oospores are
plerotic, filling the entire oogonium.
Oospore diameter averages 30 µm, but different reported dimensions can be found
in Table 60.2 of Erwin and Ribeiro (1996) (Fig. 4.13).
The oospore wall can be 2 µm thick (Waterhouse and Waterston, 1964).
Host Range and Distribution
P. syringae is
responsible for collar and fruit rot in apple, leaf spot and shoot dieback in
lilac, and pruning wound canker of almond.
It can infect 24 genera in 14 families and has been reported in Africa, Asia,
Australasia, Europe, North America, and
Symptoms
Collar and
Fruit Rot of Malus pumila (Apple):
In fruit rot, the flesh of infected tissue turns dark brown, but the rotted tissue remains firm. Collar rot occurs during late autumn, and symptoms include girdling of the trunk from the collar to several inches above the ground and exudation of gum from affected bark. During the spring, buds of young trees fail to open and mature trees put forth weak, small shoots that do not develop further. In nursery stocks, dark, slightly sunken cankers occur on stems, and in severe cases, the stem is girdled.
Leaf Spot and
Shoot Dieback of Syringa vulgaris
(Lilac):
P. syringae affects
plants during the winter dormant season and leads to small, water-soaked lesions
on leaves. The lesions gradually increase
in size during periods of frequent rainfall and eventually become irregular in
shape. The brown patches are surrounded
by lighter-colored margins and entire leaves may be invaded.
The fungus subsequently grows down the petioles into the cortex of the branches
and dark brown or black cankers form in the bark.
The vascular system is affected during advanced stages of the disease.
Occasionally, disease may be limited to a single bud (
Pruning Wound
Canker of Prunus dulcis (Almond):
P. syringae causes pruning wound cankers during the winter months. P. syringae causes gumming cankers at 2–20°C and infects plants with pruning wounds (Fig. 5).
References
Berkeley, M. J. 1881. Lilac fungus. Gard. Chron. II 16:665.
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, St. Paul, MN.
Gallegly, M., and Hong, C. 2008. Phytophthora: Identifying Species by Morphology
and DNA Fingerprints. American Phytopathological Society,
Ho, H. H., and Jong, S. C. 1993. Phytophthora hibernalis and P. syringae. Mycotaxon 47:439-460.
Höhnk, W. 1936. On three pythiaceous oomycetes. Beih. Bot. Zentralbl. 55(Abt.
A):89-99.
Jung, T., Nechwatal, J., Cooke, D. E. L., Hartmann, G. C., Blaschke, M., Oswald,
W. F.,
Klebahn, H. 1905. Eine neue Pilzkrankheit der Syringen (A new fungal disease of Syringae). Zentralbl. Bakt. 15(Abt. 2):335-336. (In German)
Klebahn, H. 1909. Die neue Zweig-und Knospenkrankheit (A new twig and bud
disease).
Pages 18-75 in: Krankheiten
des Flieders.
Kennedy, D. M., and
Pethybridge, G. H. 1913. On the rotting of potato tubers by a new species of
Phytophthora having a method of sexual reproduction hitherto undescribed.
Sci. Proc. R.
Sarejanni, J. A. 1936. La pourriture de Collet des Solanées cultivees et la
classification du genre Phytophthora
(A collar rot of cultivated Solanum
and the classification of the genus
Phytophthora). Inst. Phytopath. Benaki 2:35-52. (In French)
Sparrow, F. K., Jr. 1960. Aquatic Phycomycetes.
Stamps, D. J., Waterhouse, G. M., Newhook, F. J., and Hall, G. S. 1990. Revised tabular key to the species of Phytophthora. Mycol. Pap. 162. CAB International, Wallingford, United Kingdom; Commonwealth Mycological Institute, Kew, Surrey, England.
Tucker, C. M. 1931. Taxonomy of the genus
Phytophthora de Bary. Univ.
Waterhouse, G. M., and Waterston, J. M. 1964. Phytophthora syringae. CMI Descr. Pathog. Fungi Bact. 32.