Figure 1. Morphology of Phytophthora nicotianae (=Phytophthora parasitica). Upper row, Papillate, ovoid sporangia; germinating chlamydospore. Middle row, Papillate, ovoid sporangia; germinating oospore. Lower row, Oogonia with amphigynous antheridia containing oospores; terminal and intercalary chlamydospores. (Courtesy A. Vaziri; Reproduced from Erwin and Ribeiro, 1996) Click image to see larger view.

 

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

 

Figure 3. Sporangia of Phytophthora nicotianae. (Courtesy Courtney Gallup, North Carolina State University)

 

Figure 4. Phytophthora nicotianae (=Phytophthora parasitica). A, Colony. B, D–H, and L, Sporangia. C, Hyphal swelling. I, Chlamydospore. J and K, Oogonia and antheridia. Bar = 20 µm. All the same magnification except A and B. (Courtesy Hon H. Ho; Reproduced, by permission of the Institute of Plant and Microbial Biology, from Ho et al., 1995) Click image to see larger view.

 

Figure 5. Oospores of Phytophthora nicotianae and spherical antheridia. (Courtesy David Shew, North Carolina State University)

 

Figure 6. Black shank, caused by Phytophthora nicotianae, in a field of tobacco. (Courtesy David Shew, North Carolina State University)

 

Figure 7. Blank shank, caused by Phytophthora nicotianae, on a tobacco plant root. (Courtesy David Shew, North Carolina State University)

 

Figure 8. Pineapple with crown rot, caused by Phytophthora nicotianae. (Courtesy Jean B. Ristaino)

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Introduction

Phytophthora nicotianae  Breda de Haan (1896)

 

Phytophthora nicotianae was first described by Breda de Haan in 1896 (Breda de Haan, 1896). In 1928, Ashby noted the error in drawings of paragynous antheridia by Brenda de Haan and suspected the cultures were contaminated with a Pythium species (Ashby, 1928). The name P. nicotianae was never formally rejected under the International Code of Nomenclature. Synonyms of P. nicotianae include P. melongenae Sawada (1915), P. allii Sawada (1915), P. terrestris (as P. terrestrial) Sherb. (1917) (=Blepharospora terrestris (Sherbakoff) Peyronel (1920)), P. parasitica var. rhei G. H. Godfrey (1923), P. jatrophae Jensen (1923), P. tabaci Sawada (1927), P. parasitica var. piperina Dastur (1935), P. formosana Sawada (1942), P. lycopersici Sawada (1942), P. ricini Sawada (1942), and P. parasitica var. sesami Prasad (1957). P. parasitica var. sabdariffae is an invalid name, nom. nud. (Cline et al., 2008; Waterhouse, 1963). Until 1963, the name P. parasitica Dastur (1913), the cause of a seedling blight of castor bean (Ricinus communis), was widely accepted instead of P. nicotianae because of an inadequate description of P. nicotianae by Breda de Haan (1896). In 1963, Waterhouse replaced the name P. parasitica with the name P. nicotianae because it had priority despite the error in description by Breda de Haan. Waterhouse and Waterston (1964a; 1964b) described the varieties P. nicotianae var. nicotianae and P. nicotianae var. parasitica. The name P. nicotianae is not yet universally accepted and some individuals prefer the name P. parasitica to P. nicotianae. Until recently, the name P. parasitica has been frequently used for this species, and there has been discussion of a proposal for conservation (see discussions in Erwin and Ribeiro, 1996, p. 39; Gallegly and Hong, 2008; Ho and Jong, 1989). Varietal distinctions are no longer recognized (Erwin and Ribeiro, 1996). Hall redescribed the species in 1993 (Hall, 1993). P. nicotianae is a group II Phytophthora species (Stamps et al., 1990) (Fig. 1).

Cultural Characteristics

The optimum temperature for growth is 27–32°C, the minimum temperature for growth is 5–7°C, and the maximum temperature for growth is 37°C. Growth characteristics vary by isolate, but on potato dextrose agar, cultures are typically arachnoid, and on V-8 juice agar cultures are fluffier (Figs. 2 and 4A). Based on previous observations, a majority of cultures exhibit rosette growth types, while a few others exhibit stellate, lanose, and intermediate (intermediate between rosette and lanose) growth types (Hall, 1993).

Reproductive Structures

Asexual Structures

 

Sporangiophores:

Sporangiophores are irregularly or sympodially branched.

 

Sporangia:

Sporangia can be ellipsoid, ovoid, pyriform, obpyriform, or spherical. Papillate sporangia are produced singly or in a loose sympodium on long stalks 100–595 µm long (average 375 µm) (Thomson and Hine, 1972) (Figs. 3 and 4B, D–H, L) (Ho et al., 1995). Papillae are prominent, and occasionally two papillae occur on a single sporangium. Sporangia are noncaducous but occasionally caducous with short pedicels. Sporangia are 20–45 × 11–60 µm (average 28.53 × 40.18 µm). The length–breadth ratios are 1.1–1.7 (average 1.34).

 

Chlamydospores:

Chlamydospores are usually abundant and terminal or intercalary. Chlamydospores are 13–60 µm in diameter (average 28 µm). Chlamydospore walls are 1.5 µm thick (Fig. 4I).

 

Hyphae:

Hyphae are coenocytic and 7–10 µm in diameter. Hyphal swellings are present and have thin walls (Hall, 1993) (Fig. 4C).

 

Sexual Structures

 

Most P. nicotianae isolates are heterothallic but some can be homothallic (Brasier, 1972; Tsao et al., 1980).

 

Antheridia:

Antheridia are amphigynous and spherical or oval. Antheridia are 9–10 × 10–12 µm (Waterhouse and Waterston, 1964a; 1964b).

 

Oogonia:

Oogonia are smooth, spherical, and 15–64 µm in diameter (average 26.8 µm). Walls are 1–2 µm thick.

 

Oospores:

Oospores are aplerotic and 13–35 µm in diameter (average 22.6 µm) (Figs. 4J–K and 5). Oospore walls are 1.5–3 µm thick.

Host Range and Distribution

P. nicotianae infects a wide variety of host species and causes diseases such as root and crown rot as well as blight of fruit or foliar tissue. Some host species include tobacco, citrus, cotton, and orchid. An extensive table (Table 50.2) is presented in Erwin and Ribeiro (1996).

Symptoms

Black Shank of Nicotiana tabacum (Tobacco):

Some isolates of P. nicotianae are specifically pathogenic to tobacco and cause black shank (Lucas, 1975). Tobacco at all stages of growth is susceptible to attack. Young seedlings are susceptible to damping-off in the nursery, and when infected seedlings are transplanted, root rot can occur. During warm weather, leaves of infected plants wilt and leaves nearing maturity suddenly wilt irreversibly, turn yellow, and droop (Fig. 6). In advanced stages of the disease, dry, dark brown or black lesions develop in the cortical tissue on the stem near the soil line. The lesions can expand upward and may cover as much as half the length of the stem. The entire root system and the base of the stem may eventually decay (Fig. 7). Upon cutting a longitudinal section of the stem, it is visible that the pith of the stem is separated into platelike disks. In some varieties, the roots are the only portion of the plant affected by the disease. High temperatures, high humidity, rainfall, and high soil moisture lead to disease development.

 

Brown Rot, Foot Rot, Gummosis, and Root Rot of Citrus Species:

Infections starts at the bottom end of the fruit, and several infected areas may coalesce and cover the whole fruit. Diseased tissue is firm and leathery, and the fruit drops after becoming mummified. During wet weather, a white fungal growth often appears on the surface of the fruit, and rotted fruit emanates a pungent, rancid odor (Eckert and Brown, 1986). In areas of high rainfall, dark, water-soaked areas develop on the leaves, particularly at the tips and along the margins, and the tips die back. Severely affected leaves become black at advanced stages of the disease and drop prematurely. If orange and mandarin trees are infected, they can become completely defoliated. Brown rot develops on fruit during rainy weather. Gummosis and root rot occur during warm weather and include symptoms such as the formation of dark, water-soaked areas on the trunk close to the soil line; gum exuding from these areas based on weather and cultivar; firm diseased bark; brown staining in infected wood; yellow and gummous cambium; drying and longitudinal cracking of the bark; development of foul-smelling odor; poor fruit quality; and yellowing and premature dropping of leaves. Fibrous root rot symptoms include brown discoloration and dieback of feeder roots (Fraser, 1942; Klotz et al., 1958) and frog-eyed lesions on highly susceptible rootstocks (Klotz, 1978). Root rot can be distinguished from gummosis by the lack of gumming and the dusky to black discoloration of the wood below the bark (Klotz et al., 1967). Foot rot is similar to gummosis, but the foot rot lesions occur above the bud union (Timmer et al., 1993).

 

Heart Rot of Ananas comosus (Pineapple):

Heart rot occurs most frequently in areas of high rainfall or excessive irrigation and at 30°C (Hine et al., 1964). When infected, the terminal crown of the leaves becomes easily detached from the tree if pulled (Fig. 8). Leaves turn from green to yellowish green to red and then curl back along the edges, become smoky brown, disintegrate, and fall to the ground. Outer leaves often do not become affected until later stages of the disease, while central leaf bases become yellowish white and are bordered by a distinct margin. The fruit becomes brown and a foul smell is emitted from the plant.

 

Buckeye Rot and Root Rot of Lycopersicon esculentum (Tomato):

The pathogen causes an infection of fibrous roots and taproots of tomato. It causes zonate brown lesions on tomato fruit. Disease development is enhanced by high soil moisture, frequent irrigation, water stress, and soil or air temperatures above 20°C (Ristaino et al., 1988).

References

Ashby, S. F. 1928. The oospores of Phytophthora nicotianae Br. de Haan, with notes on the taxonomy of P. parasitica Dastur. Trans. Br. Mycol. Soc. 13:86-95.

 

Brasier, C. M. 1972. Observations on the sexual mechanism in Phytophthora palmivora and related species. Trans. Br. Mycol. Soc. 58:237-251.

 

Breda de Haan, J. van 1896. De bibitziekte in de Deli-tabak veroorzaakt door Phytophthora nicotianae (The root disease in Deli-tobacco caused by Phytophthora nicotianae). Meded. S. Lands Plantentiun 15. (In Dutch)

 

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.

 

Dastur, J. F. 1913. Phytophthora parasitica n. sp., a new disease of the castor oil plant. Mem. Dep. Agric. India Bot. Ser. 5(4):177-231.

 

Eckert, J. W., and Brown, G. E. 1986. Postharvest citrus diseases and their control. Pages 315-360 in: Fresh Citrus Fruits. W. F. Wardowski, S. Nagy, and W. Grierson, eds. AVI, Westport, CT.

 

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

 

Fraser, L. 1942. Phytophthora root rot of citrus. J. Aust. Inst. Agric. Sci. 8:101-105.

 

Gallegly, M., and Hong, C. 2008. Phytophthora: Identifying Species by Morphology and DNA Fingerprints. American Phytopathological Society, St. Paul, MN.

 

Godfrey, G. H. 1923. A Phytophthora foot rot of rhubarb. J. Agric. Res. 23:1-26.

 

Hall, G. 1993. An integrated approach to the analysis of variation in Phytophthora nicotianae and a redescription of the species. Mycol. Res. 97:559-574.

 

Hine, R. B., Alaban, C., and Klemmer, H. 1964. Influence of soil temperatures on root and heart rot of pineapple caused by Phytophthora cinnamomi and Phytophthora parasitica. Phytopathology 54:1287-1289.

 

Ho, H. H., and Jong, S. C. 1989. Phytophthora nicotianae (P. parasitica). Mycotaxon 35:243-276.

 

Ho, H. H., Ann, P. J., and Chang, H. S. 1995. The genus Phytophthora in Taiwan. Inst. Bot. Acad. Sin. Monogr. Ser. 15.

 

Kale, G. B., and Prasad, N. 1957. Phytophthora blight of Sesamum. Indian Phytopathol. 10:38-47.

 

Klotz, L. J. 1978. Fungal, bacterial, and nonparasitic diseases and injuries originating in the seedbed, nursery, and orchard. Pages 1-66 in: The Citrus Industry, Vol. IV. Crop Protection, rev. ed. W. Reuther, E. C. Calavan, and G. E. Carman, eds. University of California, Division of Agriculture and Natural Science, Berkeley, CA.

 

Klotz, L. J., DeWolfe, T. A., and Wong, P.-P. 1958. Decay of fibrous roots of citrus. Phytopathology 48:616-622.

 

Klotz, L. J., Richards, S. J., and DeWolfe, T. A. 1967. Irrigation effects on root rot of young citrus trees. Calif. Citrogr. 52:91.

 

Lucas, G. B. 1975. Black shank. Pages 115-141 in: Diseases of Tobacco. Biological Consulting Associates, Raleigh, NC.

 

Peyronel, B. 1920. Un interesante parasita del Lupino non ancora segnalato in Italia, Blepharospora terrestris (Sherb.) Peyr. Atti R. Accad. Naz. Lincei, Ser. 5. Rend. Cl. Sci. Fis. Mat. Nat. 29. I:194-197. (In Italian)

 

Ristaino, J. B., Duniway, J. M., and Marois, J. J. 1988. Influence of frequency and duration of furrow irrigation on the development of Phytophthora root rot and yield in processing tomatoes. Phytopathology 78:1701-1706.

 

Sawada, K. 1915. Two new species of the genus Phytophthora causing diseases of onion and eggplant. Spec. Bull. Agric. Exp. Stn. Gov. Formosa 11:1-139. (In Japanese)

 

Sawada, K. 1927a. Descriptive catalogue of the Formosan fungi. Part III. Rep. Dep. Agric. Res. Inst. Formosa 27:1-62 (In Japanese)

 

Sawada, K. 1927b. Descriptive catalogue of the Formosan fungi. Part IV. Rep. Dep. Agric. Res. Inst. Formosa 27:1-62. (In Japanese)

 

Sawada, K. 1942. Phytophthora species on tobacco. Formosa Agric. Rev. 38:7-12. (In Japanese)

 

Sherbakoff, C. D. 1917. Buckeye rot of tomato fruit. Phytopathology 7:119-129.

 

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.

 

Thomson, S. V., and Hine, R. B. 1972. Atypical sporangium-like structures of Phytophthora parasitica. Mycologia 64:457-460.

 

Timmer, L. W., Menge, J. A., Zitko, S. E., Pond, E., Miller, S. A., and Johnson, E. L. V. 1993. Comparison of ELISA techniques and standard isolation methods for Phytophthora detection in citrus orchards in Florida and California. Plant Dis. 77:791-796.

 

Tsao, P. H., Ugale, R., Hobbs, S., and Farih, A. 1980. Control of homothallic oospore formation in Phytophthora parasitica by culture manipulations. Trans. Br. Mycol. Soc. 75:153-156.

 

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.

 

Waterhouse, G. M., and Waterston, J. M. 1964a. Phytophthora nicotianae var. nicotianae. CMI Descr. Pathog. Fungi Bact. 34.

 

Waterhouse, G. M., and Waterston, J. M. 1964b. Phytophthora nicotianae var. parasitica. CMI Descr. Pathog. Fungi Bact. 35.