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Some species ofPythiumisolated from soil and water samples collected in western Africa
Microbiol. Res. (1994) 149,217-222
Microbiological Research ©
Gustav Fischer Verlag Jena
Some species of Pythium isolated from soil and water samples collected in western Africa Bernard Paull, Philippe Bouchet2, Fran90ise Bouchet 3 1 Laboratoire de Botanique, Faculte de Pharmacie, B.P: 83. 59006, Lille, France 2Laboratoire de Biologie Vegetale et de Cryptogamie, Faculte de Pharmacie, 51096 Reims, France 3Laboratoire de parasitologie, URA CNRS 1415, Faculte de Pharmacie, 51096 Reims, France
Accepted: May 2, 1994
Abstract Eight species of Pythium viz, P. angustatum, P. acanthicum, P. deliense, P. inflatum, P. minor, P. oligandrum, P. perilium, and P. torulosum, are described from soil and water samples
collected in Togo and Benin in the western Africa. Taxonomic and morphological details of the 8 species of fungi are dicussed in this article.
Keywords: Pythium - sporangia - antheridia - oogonia
- oospores
Introduction The genus Pythium with more than 120 species, is widely distributed. Most of these together with other microorganisms constitute the natural flora of soil and fresh water. Many species of this genus are well known plant parasites, others exist strictly as saprophytes, as a parasite on mosquito larvae (Saunders et al. 1987), and one species is known to be a mammalian pathogen (deCock et al. 1987). Very little work on this genus in particular and aquatic fungi in general has been done in the continent of Africa. Apart from some work in Nigeria (Fajola and Alasoadura 1974; 1975) and in Cameroun (Nef et al. 1991) almost nothing has been done on the genus Pythium in other adjoining countries of the Western Africa. Under a mycological and ethnobotanical tour, two of the authors from the "Faculte de Pharmacie" of Reims went to Togo and Benin in the month of August 1992 Corresponding author: B. Paul Present address: Universite de Dijon,
Science de la vie, 6 Bd. Gabriel F -21000 Dijon, France
and collected, at random, 49 soil and water samples. Pythiaceous fungi were isolated from these at the "Faculte de Pharmacie" in Lille. This is the first report of this programme in which 8 species of the genus Pythium are recorded and described.
Materials and methods Soil samples were collected in sterile disposable bottles and brought to France. Fungi were isolated using the usual baiting techniques in water described elsewhere (Plaats-Niterink 1981; Paul 1986; 1987; Hendrix and Campbell 1983). The baits used were boiled hemp-seed halves introduced either to a watery solution of the soil, or directly to the water samples. Temperature-growth relations were observed on solid media, potato carrot agar (PCA) and corn meal agar (CMA). Identification was done with the help of Keys provided by Middleton (1943), Waterhouse 1967), Plaats-Niterink (1981), and Dick (1990).
Observations and results From the 49 soil and water samples collected in Togo and Benin, aquatic fungi were isolated from most of the samples. These were mostly from the family of Pythiaceae. With the exception of Pythium oligandrum and Pythium torulosum which are quite common pythiaceous fungi, the other six species are quite rare as they have been reported from a very few localities. Pythium angus tatum Sparrow (figs 1- 3 and 42 - 44) Colonies on PCA submerged, giving a rosette pattern. Average daily growth rate on PCA at 25°C is Microbiol. Res. 149 (1994) 3
217
14
Figures 1-3: Pythium angustatum: 1: filamentous sporangia, 2: antheridia and oogonia 3: oogonia with oospores. Figs. 4-7: Pythium acanthicum 4: contiguous sporangia, 5: oogonium with monoclinous antheridium, 6 - 7: oospores; Figs. 8 -11: - Pythium deliense: 8 - 9: filamentous inflated sporangia, 10: oogonium bending towards antheridium, 11: oogonium containing an oospore: 12-17: Pythium injlatum 12: filamentous inflated sporangia, 13: catenulate oogonia, 14: oogonium with diclinous antheridia, 15-17: oospores.
6 mm. Main hyphae up to 5 /lm wide. Sporangia filamentous, slightly inflated. Oogonia terminal or intercalary, sometimes in chains of upto 4 oogonia, spherical, smooth walled, 13 - 34 (av. 21.5) /lm diam. Antheridia of monoclinous or diclinous origin, 1 - 7 per oogonium, much branched giving 1- 5 antheridial cells all crowding around the oogonia. Oospores spherical, aplerotic, usually single, but at times up to 3 per oogoni; 11-22 (av.16.3) /lm diam. Wall 1 - 2 /lm thick. 218
Microbiol. Res. 149 (1994) 3
This isolate (T-12) was obtained from a water sample taken in Aledjo in the Republic of togo. Apart from its slow growth and sometimes catenulate oogonia, most of the features fit closely the description of the species found in the literature. Pythium acanthicum Drechsler (figs 4 - 7 and 45) Colonies on PCA submerged, without a distinct pattern. Average daily growth rate on PCA at 25°C is
Figures 18-23: Pythium minor: 18-20 : hypha) bodies, 21-22: antheridia and oognia, 23: oospores; 24-29: Pythium oligandrum : 24-25: contiguous sporangia, 26-27: ornamented oogonia, 28-29 : oospores; 30-34: Pythiumperilium : 30: filamentous inflated sporangia, 31 : antheridia and oogonia, 32-34: oospores; 35-41: Pythium torulosum: 35: filamentous inflated sporangia, 36-38: oogonia and monoclinous antheridia, 39-41: oospores.
22 mm. Main hyphae up to 5 /lm wide. Sporangia intercalary and terminal, spherical, oval, oblong to cylindrical, usually connected by filamentous and contiguous elements. The spherical elements of the sporangia can be up to 30 /lm in diam., usually germinating by germ tubes. Oogonia usually termi-
nal, at times intercalary, 17 - 25 /lm diam., (av. 21 /lm)., walls ornamented with conical and blunt projections measuring 1.5 - 3 /lm in length and up to 3 /lm broad at the base. Antheridia monoclinous, terminal, 1- 2 per oogonium, antheridial cells sometimes constricted, making broad ventral Microbiol. Res. 149 (1994) 3
219
43
20}Lm
45
Figures 42 - 44: Pythium angustatum: 42: filamentous slightly inflated sporangia, 43 : oogonium with many antheridia, 44: oospores; 45: Pythium acanthicum: antheridia and ornamented oogonia, 46: Pythium injlatum: oogonium with diclinous antheridia, 47 - 48: Pythium per ilium: 47: filamentous inflated sporangia, 48: oospores.
220
Microbio!. Res. 149 (1994) 3
contact with the oogonia. Oospores spherical, mostly plerotic, 16-22 (av.19.3)!lm diam. Wall 1.4 - 3 !lm thick. This isolate (T-22.C) was obtained from a moist soil sample taken in Natitingou in Benin. Most of the features of this isolate are in common to those described elsewhere. Pythium deliense M eurs (figs 8 -11) Colonies on PCA forming moderate amount of aerial mycelium, with an average daily growth rate of 27 mm on this medium at 25°C. Main hyphae up to 10!lm wide. Sporangia filamentous, inflated, composed of elongated to irregular swollen elements. Zoospores not observed. Oogonia mostly terminal, spherical, to slightly ovoidal, 16 - 26 (av. 21) !lm diam., oogonial stalks bending towards the antheridium. Antheridia usually monoclinous, sometimes diclinous, both terminal and intercalary, usually single, rarely two per oogonium. Oospores spherical, aplerotic, one per oogonium with a regular size of 15-18!lm (av. 17) diam., provided with a regularly thin wall of approximately 1.5 !lm thick. Pythium deliense is closely related to Pythium aphanidermatum, but can be easily separated from this by the characteristic feature of the oogonial stalk bending towards the antheridium. It was also isolated from a moist soil sample taken in Natitingou in Benin (T-22 B). Pythium inflatum Matthews (figs 12 -17 and 46) Colonies in CMA & PCA submerged, giving a chrysanthemum pattern. Daily growth rate on PCA at 25°C 11 mm. Main hyphae 4 - 5 !lm wide. Sporangia filamentous, inflated with straight, irregular, or spherical elements. Zoospores and vesicles not observed. Oogonia smooth walled, globose, intercalary, catenulate, or terminal 13 - 37 (av. 22)!lm diam. Antheridia usually 1 (rarely 2) per oogonium, diclinous, and at times monoclinous, antheridial cells making a narrow apical contact with the oogonia. Oospores globose, plerotic, one per oogonium, 16-21 (av.18.3)!lm diam., and provided with a wall of 1.25 - 3 !lm. Pythium inflatum (T -26) is a rare fungus. It has been reported from few countries. This species was isolated only once, from a water sample taken in Toukountouna in the Republic of Benin. This is the first report of its presence in Africa. The isolate has most of the characcters of the one described by Plaats-Niterink (1981). Some minor differences like the presence of catenulate oogonia, at times monoclinous antheridia, and the absence of zoospore formation, have been observed. The presence of very large oogonia (up to
37 !lm) was also observed but these are mostly abortive. Pythium minor Ali-Shatayeh and Dick (figs 18 - 23) Colonies on CMA and PCA submerged showing an indistict rosette pattern on the latter. Daily growth rate on PCA at 25°C is 1 mm. Main hyphae up to 6!lm wide. Sporangia and zoospores not formed. Hyphal bodies produced plentifully on solid as well as in water on hemp seed halves. These are usually intercalary, rarely terminal, globose, ovoid to cylindrical, measuring 10-23 (av. 17.1)!lm diam. Oogonia terminal, infrequently intercalary, globose, ovoid, smooth walled, measuring 14-20 (av. 16)!lm diam. Antheridia monoclinous, much branched, giving a coralloid structure and the branches tending towards the oogonium, providing 1- 2 antheridial cells to the latter. Oospores globose, 1- 2 per oogonium, aplerotic and at times plerotic, 11-15 (av. 12.4) !lm diam., with a very thin wall of 0.75-1!lm. Pythium minor (T -28) was isolated only once from a soil sample collected in Toukountouna in the republic of Benin. Ali-Shtayeh and Dick (1985) reported P. minor as a new species from U.K. Ever since it has been found as a frequently occurring species in the north of France (Paul, unpublished) This is the first report of its presence in African soil. The species is easily distinguishable from other species because of its branched antheridia forming a coralloid structure around the oogonia, small oogonia and oospores, and slow growth. However there are some differences between this isolate and the one described by Ali-Shtayeh and Dick (1985): the hyphal bodies in this case are much smaller (10 - 23 !lm instead of 20-40 !lm); more than 2 oospores per oogonium were not found as compared to up to 6, and the oospores are mostly aplerotic in this case whereas the isolate described from U.K. has strictly plerotic oospores. Pythium oligandrum Drechsler (figs 24 - 29) Colonies on CMA & PCA produce scanty aerial mycelium without any pattern on the latter. Average daily growth on PCA at 25°C is 29 mm. Main hyphae are up to 7!lm wide. Sporangia are contiguous composed of globose, ovoidal, ellipsoidal to somewhat cylindrical elements connected with hyphal elements. Oogonia terminal or intercalary, measuring 17 to 32!lm diam., (av. 24.9 !lm), provided with conical mammiform to pointed protuberances which are up to 9 !lm long and up to 6 !lm broad at the base. Antheridia mostly lacking, at times monoclinous, one to two per oogonium. Oospores globose, aplerotic and plerotic, one per oogonium, measuring 19 - 30 (av. 21)!lm diam., provided with a wall of 1- 2.5 !lm thick (av. 1.7 !lm). Microbial. Res. 149 (1994) 3
221
The above description is of isolate no. T-15, isolated from a soil sample taken in Aledjo in the Republic of Togo. Most of the features of this fungus resemble those found in the literature. The only difference worth mentioning is the absence of zoospores in spite of the presence of sporangIa. Pythium per ilium Drechsler (figs 30 - 24 and 47 - 48) Colonies on PCA submerged, showing a narrow chrysanthemum pattern. Daily growth rate on PCA at 25°C is 14 mm. Main hyphae upto 5-6 J..Lm wide. Sporangia filamentous, inflated consisting mainly of irregularly swollen elements. Oogonia terminal or intercalary, globose to somewhat elongated, smooth walled, 11-28 (av. 21) J..Lm diam. Antheridia monoc1inous and dic1inous, much branched, stalks bearing upto 8 antheridial cells per oogonium. Oospores globose, plerotic, 10-25 (av. 18.9) J..Lm diam. Wall 1 - 3 J..Lm thick. Pythiumperilium (T-18) is also a rare fungus. It was isolated from water samples collected in "Tamberma land" in the Republic of Togo. This isolate resembles in most of its aspects one described by PlaatsNiterink (1981). The only difference worth mentioning is the presence of up to 8 antheridial cells per oogonium instead of up to 5. Pythium torulosum Coker and Paterson (figures 35-41) Colonies on CMA and PCA submerged, on PCA showing a radiate pattern and growing with an average daily growth rate of 14 mm at 25°C. Main hyphae up to 5 - 6 J..Lm wide. Sporangia consisting of filamentous inflated, toruloid elements. Oogonia terminal or at times intercalary, globose, sub-globose, 13-22 (av. 17.4J..Lm) diam. Antheridia monocolinous, 1- 2 per oogonium, antheridial cells making apical contact with the oogonia. Oospores globose, plerotic, single 9 - 20 (av. 16.8) J..Lm diam. Wall 1- 2 J..Lm in thickness. Pythium torulosum was isolated from soil samples collected near a waterfall in Tanoungou in the republic of Benin (T -38). Apart from slightly bigger oogonia an slightly greater distance between the origin of antheridial stalk and the oogonium (up to 30 J..Lm instead of 12 J..Lm described by Plaats-Niterink 1981) all the other characters of this isolate resemble the description of P. torulosum found in the literature.
222
Microbiol. Res. 149 (1994) 3
Acknowledgements
The authors are thankful to Professor Dr. John Webster of the University of Exeter, U.K. for reveiwing this article and for making valuable suggestions and corrections. Thanks are also due to Professor. A Delelis of the "Reseau de synecologie vegetale" at the "Faculte de pharmacie" of Lille in France for her encouragements and financial help towards the publication of this paper. References
Ali-Shtayeh, M. S., Dick, M. W (1985): Five new species of Pythium (Peronosporomycetidae). Botanical Journal of the Linnean Society 91, 297 - 317. deCock, A W A M., Mendoza, L., Padhye, A A, Ajello, L., Kaufman, L. (1987): Pythium insidiosum sp. nov., the etiologic agent of pythiosis. J. Clin. Micro. 25, 344-349. Dick, M. W, (1990): Keys to Pythium. University of Reading Press, 64. Fajola, A. 0., Alasoadura, S. O. (1974): Studies on the damping - off disease of tobacco (Nicotiana tabacum) in Nigeria. Mycopath. Mycol. appl. 52, 239 - 249. Fajola, A. 0., Alasoadura, S. O. (1975): Antagonistic effects of Trichoderma harzianum on Pythium aphanidermatum causing the damping-of diseases of tobacco in Nigeria. Mycologia 57, 47 - 52. Hendrix, F. F., Campbell, W D. (1983): Some pythiaceous fungi - new roles for old organisms. In: Zoosporic plant pathogens, a Modern Perspective. (Ed.: Buczacki, S. T.) Academic Press New York, 123-160. Middleton, J. T. (1943): The taxonomy, host range, and geographical distribution of the genus Pythium. Mem. torrey Bot. Club 20, 1-171. Nef, C., Rio, B., Chrestin, H. (1991): Induction of catharan thine synthesis and stimulation of major indole alkaloids production by Catharanthus roseus cells under non-growth-altering treatment with Pythium vexans extracts. Plant C. R. 10,26-29. Paul, B. (1986): An aquatic species, Pythium toruloides sp. nov., from Algeria. Trans. Brit. Mycol. Soc. 89, 195-198. Paul, B. (1987): A new species of Pythium with ornamented oogonia from Algeria. Mycologia, 79, 797 - 802. Plaats-Niterink, A J. van der (1981): Monograph of the genus Pythium. Studies in Mycology Baarn 21, 1- 242. Saunders, G. A, Washburn, J. 0., Egerter, D. E., Anderson, J. A (1988): Pathogenicity of fungi isolated from field-collected larvae of the western treehole mosquito, Aedes sierrensis (Diptera: Culicidae). J. Invert. Path. 52, 360-363. Waterhouse, G. M. (1967): Key to Pythium Pringsheim. Mycological P. CMI. 109, 1-15.
Microbiological Research ©
Gustav Fischer Verlag Jena
Some species of Pythium isolated from soil and water samples collected in western Africa Bernard Paull, Philippe Bouchet2, Fran90ise Bouchet 3 1 Laboratoire de Botanique, Faculte de Pharmacie, B.P: 83. 59006, Lille, France 2Laboratoire de Biologie Vegetale et de Cryptogamie, Faculte de Pharmacie, 51096 Reims, France 3Laboratoire de parasitologie, URA CNRS 1415, Faculte de Pharmacie, 51096 Reims, France
Accepted: May 2, 1994
Abstract Eight species of Pythium viz, P. angustatum, P. acanthicum, P. deliense, P. inflatum, P. minor, P. oligandrum, P. perilium, and P. torulosum, are described from soil and water samples
collected in Togo and Benin in the western Africa. Taxonomic and morphological details of the 8 species of fungi are dicussed in this article.
Keywords: Pythium - sporangia - antheridia - oogonia
- oospores
Introduction The genus Pythium with more than 120 species, is widely distributed. Most of these together with other microorganisms constitute the natural flora of soil and fresh water. Many species of this genus are well known plant parasites, others exist strictly as saprophytes, as a parasite on mosquito larvae (Saunders et al. 1987), and one species is known to be a mammalian pathogen (deCock et al. 1987). Very little work on this genus in particular and aquatic fungi in general has been done in the continent of Africa. Apart from some work in Nigeria (Fajola and Alasoadura 1974; 1975) and in Cameroun (Nef et al. 1991) almost nothing has been done on the genus Pythium in other adjoining countries of the Western Africa. Under a mycological and ethnobotanical tour, two of the authors from the "Faculte de Pharmacie" of Reims went to Togo and Benin in the month of August 1992 Corresponding author: B. Paul Present address: Universite de Dijon,
Science de la vie, 6 Bd. Gabriel F -21000 Dijon, France
and collected, at random, 49 soil and water samples. Pythiaceous fungi were isolated from these at the "Faculte de Pharmacie" in Lille. This is the first report of this programme in which 8 species of the genus Pythium are recorded and described.
Materials and methods Soil samples were collected in sterile disposable bottles and brought to France. Fungi were isolated using the usual baiting techniques in water described elsewhere (Plaats-Niterink 1981; Paul 1986; 1987; Hendrix and Campbell 1983). The baits used were boiled hemp-seed halves introduced either to a watery solution of the soil, or directly to the water samples. Temperature-growth relations were observed on solid media, potato carrot agar (PCA) and corn meal agar (CMA). Identification was done with the help of Keys provided by Middleton (1943), Waterhouse 1967), Plaats-Niterink (1981), and Dick (1990).
Observations and results From the 49 soil and water samples collected in Togo and Benin, aquatic fungi were isolated from most of the samples. These were mostly from the family of Pythiaceae. With the exception of Pythium oligandrum and Pythium torulosum which are quite common pythiaceous fungi, the other six species are quite rare as they have been reported from a very few localities. Pythium angus tatum Sparrow (figs 1- 3 and 42 - 44) Colonies on PCA submerged, giving a rosette pattern. Average daily growth rate on PCA at 25°C is Microbiol. Res. 149 (1994) 3
217
14
Figures 1-3: Pythium angustatum: 1: filamentous sporangia, 2: antheridia and oogonia 3: oogonia with oospores. Figs. 4-7: Pythium acanthicum 4: contiguous sporangia, 5: oogonium with monoclinous antheridium, 6 - 7: oospores; Figs. 8 -11: - Pythium deliense: 8 - 9: filamentous inflated sporangia, 10: oogonium bending towards antheridium, 11: oogonium containing an oospore: 12-17: Pythium injlatum 12: filamentous inflated sporangia, 13: catenulate oogonia, 14: oogonium with diclinous antheridia, 15-17: oospores.
6 mm. Main hyphae up to 5 /lm wide. Sporangia filamentous, slightly inflated. Oogonia terminal or intercalary, sometimes in chains of upto 4 oogonia, spherical, smooth walled, 13 - 34 (av. 21.5) /lm diam. Antheridia of monoclinous or diclinous origin, 1 - 7 per oogonium, much branched giving 1- 5 antheridial cells all crowding around the oogonia. Oospores spherical, aplerotic, usually single, but at times up to 3 per oogoni; 11-22 (av.16.3) /lm diam. Wall 1 - 2 /lm thick. 218
Microbiol. Res. 149 (1994) 3
This isolate (T-12) was obtained from a water sample taken in Aledjo in the Republic of togo. Apart from its slow growth and sometimes catenulate oogonia, most of the features fit closely the description of the species found in the literature. Pythium acanthicum Drechsler (figs 4 - 7 and 45) Colonies on PCA submerged, without a distinct pattern. Average daily growth rate on PCA at 25°C is
Figures 18-23: Pythium minor: 18-20 : hypha) bodies, 21-22: antheridia and oognia, 23: oospores; 24-29: Pythium oligandrum : 24-25: contiguous sporangia, 26-27: ornamented oogonia, 28-29 : oospores; 30-34: Pythiumperilium : 30: filamentous inflated sporangia, 31 : antheridia and oogonia, 32-34: oospores; 35-41: Pythium torulosum: 35: filamentous inflated sporangia, 36-38: oogonia and monoclinous antheridia, 39-41: oospores.
22 mm. Main hyphae up to 5 /lm wide. Sporangia intercalary and terminal, spherical, oval, oblong to cylindrical, usually connected by filamentous and contiguous elements. The spherical elements of the sporangia can be up to 30 /lm in diam., usually germinating by germ tubes. Oogonia usually termi-
nal, at times intercalary, 17 - 25 /lm diam., (av. 21 /lm)., walls ornamented with conical and blunt projections measuring 1.5 - 3 /lm in length and up to 3 /lm broad at the base. Antheridia monoclinous, terminal, 1- 2 per oogonium, antheridial cells sometimes constricted, making broad ventral Microbiol. Res. 149 (1994) 3
219
43
20}Lm
45
Figures 42 - 44: Pythium angustatum: 42: filamentous slightly inflated sporangia, 43 : oogonium with many antheridia, 44: oospores; 45: Pythium acanthicum: antheridia and ornamented oogonia, 46: Pythium injlatum: oogonium with diclinous antheridia, 47 - 48: Pythium per ilium: 47: filamentous inflated sporangia, 48: oospores.
220
Microbio!. Res. 149 (1994) 3
contact with the oogonia. Oospores spherical, mostly plerotic, 16-22 (av.19.3)!lm diam. Wall 1.4 - 3 !lm thick. This isolate (T-22.C) was obtained from a moist soil sample taken in Natitingou in Benin. Most of the features of this isolate are in common to those described elsewhere. Pythium deliense M eurs (figs 8 -11) Colonies on PCA forming moderate amount of aerial mycelium, with an average daily growth rate of 27 mm on this medium at 25°C. Main hyphae up to 10!lm wide. Sporangia filamentous, inflated, composed of elongated to irregular swollen elements. Zoospores not observed. Oogonia mostly terminal, spherical, to slightly ovoidal, 16 - 26 (av. 21) !lm diam., oogonial stalks bending towards the antheridium. Antheridia usually monoclinous, sometimes diclinous, both terminal and intercalary, usually single, rarely two per oogonium. Oospores spherical, aplerotic, one per oogonium with a regular size of 15-18!lm (av. 17) diam., provided with a regularly thin wall of approximately 1.5 !lm thick. Pythium deliense is closely related to Pythium aphanidermatum, but can be easily separated from this by the characteristic feature of the oogonial stalk bending towards the antheridium. It was also isolated from a moist soil sample taken in Natitingou in Benin (T-22 B). Pythium inflatum Matthews (figs 12 -17 and 46) Colonies in CMA & PCA submerged, giving a chrysanthemum pattern. Daily growth rate on PCA at 25°C 11 mm. Main hyphae 4 - 5 !lm wide. Sporangia filamentous, inflated with straight, irregular, or spherical elements. Zoospores and vesicles not observed. Oogonia smooth walled, globose, intercalary, catenulate, or terminal 13 - 37 (av. 22)!lm diam. Antheridia usually 1 (rarely 2) per oogonium, diclinous, and at times monoclinous, antheridial cells making a narrow apical contact with the oogonia. Oospores globose, plerotic, one per oogonium, 16-21 (av.18.3)!lm diam., and provided with a wall of 1.25 - 3 !lm. Pythium inflatum (T -26) is a rare fungus. It has been reported from few countries. This species was isolated only once, from a water sample taken in Toukountouna in the Republic of Benin. This is the first report of its presence in Africa. The isolate has most of the characcters of the one described by Plaats-Niterink (1981). Some minor differences like the presence of catenulate oogonia, at times monoclinous antheridia, and the absence of zoospore formation, have been observed. The presence of very large oogonia (up to
37 !lm) was also observed but these are mostly abortive. Pythium minor Ali-Shatayeh and Dick (figs 18 - 23) Colonies on CMA and PCA submerged showing an indistict rosette pattern on the latter. Daily growth rate on PCA at 25°C is 1 mm. Main hyphae up to 6!lm wide. Sporangia and zoospores not formed. Hyphal bodies produced plentifully on solid as well as in water on hemp seed halves. These are usually intercalary, rarely terminal, globose, ovoid to cylindrical, measuring 10-23 (av. 17.1)!lm diam. Oogonia terminal, infrequently intercalary, globose, ovoid, smooth walled, measuring 14-20 (av. 16)!lm diam. Antheridia monoclinous, much branched, giving a coralloid structure and the branches tending towards the oogonium, providing 1- 2 antheridial cells to the latter. Oospores globose, 1- 2 per oogonium, aplerotic and at times plerotic, 11-15 (av. 12.4) !lm diam., with a very thin wall of 0.75-1!lm. Pythium minor (T -28) was isolated only once from a soil sample collected in Toukountouna in the republic of Benin. Ali-Shtayeh and Dick (1985) reported P. minor as a new species from U.K. Ever since it has been found as a frequently occurring species in the north of France (Paul, unpublished) This is the first report of its presence in African soil. The species is easily distinguishable from other species because of its branched antheridia forming a coralloid structure around the oogonia, small oogonia and oospores, and slow growth. However there are some differences between this isolate and the one described by Ali-Shtayeh and Dick (1985): the hyphal bodies in this case are much smaller (10 - 23 !lm instead of 20-40 !lm); more than 2 oospores per oogonium were not found as compared to up to 6, and the oospores are mostly aplerotic in this case whereas the isolate described from U.K. has strictly plerotic oospores. Pythium oligandrum Drechsler (figs 24 - 29) Colonies on CMA & PCA produce scanty aerial mycelium without any pattern on the latter. Average daily growth on PCA at 25°C is 29 mm. Main hyphae are up to 7!lm wide. Sporangia are contiguous composed of globose, ovoidal, ellipsoidal to somewhat cylindrical elements connected with hyphal elements. Oogonia terminal or intercalary, measuring 17 to 32!lm diam., (av. 24.9 !lm), provided with conical mammiform to pointed protuberances which are up to 9 !lm long and up to 6 !lm broad at the base. Antheridia mostly lacking, at times monoclinous, one to two per oogonium. Oospores globose, aplerotic and plerotic, one per oogonium, measuring 19 - 30 (av. 21)!lm diam., provided with a wall of 1- 2.5 !lm thick (av. 1.7 !lm). Microbial. Res. 149 (1994) 3
221
The above description is of isolate no. T-15, isolated from a soil sample taken in Aledjo in the Republic of Togo. Most of the features of this fungus resemble those found in the literature. The only difference worth mentioning is the absence of zoospores in spite of the presence of sporangIa. Pythium per ilium Drechsler (figs 30 - 24 and 47 - 48) Colonies on PCA submerged, showing a narrow chrysanthemum pattern. Daily growth rate on PCA at 25°C is 14 mm. Main hyphae upto 5-6 J..Lm wide. Sporangia filamentous, inflated consisting mainly of irregularly swollen elements. Oogonia terminal or intercalary, globose to somewhat elongated, smooth walled, 11-28 (av. 21) J..Lm diam. Antheridia monoc1inous and dic1inous, much branched, stalks bearing upto 8 antheridial cells per oogonium. Oospores globose, plerotic, 10-25 (av. 18.9) J..Lm diam. Wall 1 - 3 J..Lm thick. Pythiumperilium (T-18) is also a rare fungus. It was isolated from water samples collected in "Tamberma land" in the Republic of Togo. This isolate resembles in most of its aspects one described by PlaatsNiterink (1981). The only difference worth mentioning is the presence of up to 8 antheridial cells per oogonium instead of up to 5. Pythium torulosum Coker and Paterson (figures 35-41) Colonies on CMA and PCA submerged, on PCA showing a radiate pattern and growing with an average daily growth rate of 14 mm at 25°C. Main hyphae up to 5 - 6 J..Lm wide. Sporangia consisting of filamentous inflated, toruloid elements. Oogonia terminal or at times intercalary, globose, sub-globose, 13-22 (av. 17.4J..Lm) diam. Antheridia monocolinous, 1- 2 per oogonium, antheridial cells making apical contact with the oogonia. Oospores globose, plerotic, single 9 - 20 (av. 16.8) J..Lm diam. Wall 1- 2 J..Lm in thickness. Pythium torulosum was isolated from soil samples collected near a waterfall in Tanoungou in the republic of Benin (T -38). Apart from slightly bigger oogonia an slightly greater distance between the origin of antheridial stalk and the oogonium (up to 30 J..Lm instead of 12 J..Lm described by Plaats-Niterink 1981) all the other characters of this isolate resemble the description of P. torulosum found in the literature.
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Microbiol. Res. 149 (1994) 3
Acknowledgements
The authors are thankful to Professor Dr. John Webster of the University of Exeter, U.K. for reveiwing this article and for making valuable suggestions and corrections. Thanks are also due to Professor. A Delelis of the "Reseau de synecologie vegetale" at the "Faculte de pharmacie" of Lille in France for her encouragements and financial help towards the publication of this paper. References
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