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A preliminary survey of fungi in some Sudan soils
[ 357 ] Trans. Brit. mycol. Soc. 39 (3), 357-360 (1956).
A PRELIMINARY SURVEY OF FUNGI IN SOME
SUDAN SOILS By M. A. NOUR Faculty of Agriculture, University College
if Khartoum
This was the first attempt in the Sudan to investigate the microscopic fungi inhabiting the soil. The Waksman dilution method, Warcup's soil-plate method and Cheaters's immersion-tube technique were used for ten soil samples from the top 6 in. at ten sites. A list of the isolated fungi is given. Few qualitative differences were observed between the species of fungi found in different soils.
Clouston (1935-40) isolated some fungi from roots in the Gezira soil but no other records have been found. It has therefore been imperative to aim first at finding which fungi are present rather than which are the more active in the soil. The Waksman dilution method (1922), as recommended by Brierley (1923), was therefore chiefly used, but the Wareup (1950) and Chesters (1948) techniques were also tried. For Waksman's method, five culture media were used, namely Waksman's, modified Waksman (dextrose, 20 g.; asparagin, 2 g.; MgS0 4 • 7H20, 0'5 g.; FeCla , o· I g.; NaCl, 0'5 g.; and agar 20 g.; distilled water 1000 mI.), Conn's, Czapek-Dox and soil-extract agar, at incubation temperatures varying over the range 29-34 0 C. The fungi that appeared were more or less the same on all media. However, overgrowth of Rhizopus in the first two rendered them less suitable for the dilution method. By comparison, the other three media are less rich, and therefore have proved more suitable, particularly when acidified or used with rose bengal. Acidification of the media to a pH 4'5-5 was found necessary to check the overwhelming growth of bacteria which appeared at pH 5'5 or more. Rose bengal at I: 15,000 was not as effective in its suppression of the bacteria or of Rhizopus as was found by Dawson & Dawson (1947). There was no significant difference, however, between media made up with rose bengal, at I: 15,000 or I: 10,000, and acidified media in the numbers and types of fungi growing on them. Rose bengal considerably limited the growth in diameter of all the fungi, and particularly so at I : 5000. Inoculations of bacteria, R. stolonifer and other fungi were made on all media, for comparison with the findings from soil dilution plates, under the same conditions. The directives in Brierley, Jewson & Brierley (1927) were followed. Soils from ten different sites were sampled from the top 6 in., and their moisture and clay contents were determined. All samples came from heavy sodium-alkaline clay soils from a locality some 7 miles north of Khartoum on the east bank of the Nile, except one less alkaline silt soil from a site near the river bank.
358
Transactions Britisb Mycological Society
The soils in the order examined were: Soil I. Rich in organic debris. The sample was obtained from a plot containing the crowns and roots of cut dura hay (Sorghum vulgare). Collected in August. Clay content 30 %. Moisture content 10'5. Soil II. From same plot as I above, collected 4 weeks later. Clay content 30 %. Moisture content 6·8. Soil III. Same plot as I; collected 12 weeks later. Clay content 30%. Moisture content 6'3. Soil IV. Virgin soil. Vegetation sparse; fairly abundant only during the rainy season (July to September); sample collected in November. Clay content 20 %. Moisture content 3.8. Soil V. Same as IV above, collected in February. Clay content 15 %. Moisture content 3'7. Soil VI. River silt, collected 2 ft. from the edge of the Nile in October, before the typical 'gerf' vegetation had started. Clay content 15 %. Moisture content 18'5. Soil VII. Same as VI above, collected 8 weeks later; 'gerf' vegetation present. Clay content 15 %. Moisture content 4'9. Soil VIII. Under Medicago sativa, collected in July. Clay content 35 %. Moisture content 17'2. Soil IX. Same as VIII above, collected 6 weeks later. Clay content 35 %. Moisture content 10'5. Soil X. Fallow for 6 months succeeding crop of Medicago sativa, collected in June. Clay content 35 %. Moisture content 6.5. Duplicate plates were used for soil dilutions of I: 20,000, I :40,000 and I : 100,000, in order to obtain a suitable dilution for a counting and examination. Counts were made on the third and fourth days. Sporulation occurred in most cases on the third day; complete overcrowding of colonies occurred on the fifth day, and by the eighth day the perithecial state of some Aspergilli, e.g. Aspergillus nidulans, completely replaced the conidial state. The numbers of fungi per gram of soil were consistently too high to be anything but largely a development of colonies from spores. Growth appeared in less than 36 hr. on all media; bacterial growth predominated within 3 days at the natural pH values of the media. Acidification to pH 4'5-5 was therefore necessary, using sulphuric acid with bromocresol green indicator and a 'Lovibond' comparator. The fungi grew well on all media and produced asexual spores on the third day, covering the plates completely by then, where rose bengal was not used. For the Chesters immersion tube and the Warcup soil-plate technique, plain agar (instead of nutrient agar as in Warcup, 1950) was used. Rhizopus stolonifer, Aspergillus nidulans, A. niger, A.flavus, Curvularia lunata, Alternaria tenuis, and Fusarium solani have been the most frequent fungi isolated by these three methods. They have appeared in most soils (see Table I); they were the dominant isolates not only with the Waksman method, where they may have been largely represented by their spores (Conn, 1918; McLennan, 1928), but also when the other two methods with plain agar were used.
359
Sudan soilfungi. M. A. Nour Table
I.
Occurrence
riffungi in samples rif Sudan soil (For details see text)
Name of organism Pythium aphanidermatum (Edson) Fitz, Pythium sp. Absidia blakesleeana Lendn. Rhizopus stolonifer (Ehrenb. ex Fr.) Lind R. arrhieus Fischer (syn, R. nodosus) Mucor hiernalis Wehmer M. circinelloides van Tiegh. Thamnidium (? elegans) Syncephalastrum racemosum (Cohn) Schroet. Helicostylum pyriforme Bain. Aspergillus niger van Tiegh. A. nidulans (Eid.) Wint. A. terreus Thom A. melleus Yukawa A. sydowi (Bain. & Sart.) Thom & Church A.jlavus Link ex Fr. A. versicolor (Vuill.) Tirab. A. flauipes Bain, & Sarto A. tamarii Kita A. nidulans (Eid.) Wint. var.nov. A. candidus Link ex Fr. A.fumigatus Fresen. var.nov, Penicillium funiculosum Thom P. corylophilum Dierckx Paecilomyces uarioti Bain, Gliocladium roseum Bain, Alternaria tenuis Nees Curvularia lunata (Wakker) Boedijn Cladosporium cladosporioides (Fres.) De Vries C. sphaerospermum Penzig Triclwthecium sp. Thielaoia sp, Fusarium solanisensu Snyder & Hansen F. scirpi Lamb. & Fautr, var. compactum Wr. Corticium solani (Prill. & De1acr.) Bourd. & Galz. Total number of species
,
A
I
I
II
III
x
x x
X
x
x x
x x
x x
x
x
IV
V
VI
VII VIII IX
x
x
X x
x
x
x
x
x x x
x
x
x
x
x
x
x
x x x x
x
x
x x x x x x
x x x x x x
x x x x x x
x x x x
x x x
x x x x
x x x x
x x x x x x
x x x
x x x
x x x
x x
x x x
x x
x x
x x
x x
x
x
x
x
x
x x
x x
x
x
x
26
28
29
x x x
x x x
x x
x
x x x x x
x x x x x x
x x x x x x
x x x x x
x x
x x x
x x x
x x x x
x x x
x
x
x x
x
x
x
x
x x x
x x x
x x x x x
x
x
x
x
x
x
x
x
x
21
22
22
x x
x
x x x
x x x x x x x x x X
9
8
8
26
CONCLUSION
The fungi obtained by the different methods are similar in type and in degree of prevalence to those recorded from similar soils in other warm countries (Sabet 1935; Chaudhuri & Sachar, 1934; Todd, 1932; Jensen, 1931; Waksman, 1917; Werkenthin, 1916). Although climate and soil are closely interdependent, it appears that climatic more than edaphic similarities have resulted in this similarity of soil fungal floras. I am grateful to the Director and staff of the Commonwealth Mycological Institute for their help in the identification of the fungi. Voucher
360
Transactions British Mycological Society
cultures are available in the mycological herbaria of the C.M.I. and the Faculty of Agriculture, Khartoum North. I am also grateful to Mr G. A. Worral for assistance in the soil analyses. REFERENCES BRIERLEY, W. B. (1923). The occurrence of fungi in soil. In Russell, E. J., The microorganisms of the soil. London: Longmans, Green & Co. BRIERLEY, W. B.,]EWSON, S. T. & BRIERLEY, M. (1927). The quantitative study of soil fungi. Proc. 1St Int. Congr. Soil Sci. 3, 48-71. CHAUDHURI, H. & SACHAR, G. S. (1934)' A study of the fungus flora of the Punjab soils. Ann mycol., Berl., 22, 90-100. CHESTERS, C. G. C. (1948). A contribution to the study offungi in the soil. Trans. Brit. mycol, Soc. 30, 100-117. CLOUSTON, T. W. (1935-40). Rep. Sudan Res. Div. CONN, H. ]. (19 I 8). The microscopic study of bacteria and fungi in the soil. Tech. Bull. N.r. St. agric. Exp, Sta., no. 64. DAWSON, V. T. & DAWSON, R. C. (1947). Further observations on the use of rose bengal for enumeration of soil fungi. Proc. Soil Sci. Soc. A mer. 1946, 267-269. JENSEN, H. L. (1931). The fungus flora of the soil. Soil Sci. 31, 123-158. McLENNAN, E. (1928). The growth of fungi in soil. Ann appl. Biol. 15, 95-109. SABET, Y. S. (1935). A preliminary study of the Egyptian soil fungi. Bull. Fac. Sci. Egypt. Univ.5, 1-29. TODD, R. L. (1932). Phycomycetes, Ascomycetes and Fungi Imperfecti in Oklahoma soils. Science, 76, 464. WAKSMAN, S. A. (1917). Is there any fungus flora of the soil? Soil Sci. 3, 565-589. WAKSMAN, S. A. (1922). A method for counting the number offungi in the soil. ]. Bact. 7,339-341. WARCUP,]. H. (1950). The soil-plate method for isolation of fungi from soil. Nature, Lond., 166, 117. WERKENTHIN, F. C. (1916). Fungus flora of Texas soils. Phytopathology, 6, 241-253.
(Acceptedfor publication 18 November 1955)
A PRELIMINARY SURVEY OF FUNGI IN SOME
SUDAN SOILS By M. A. NOUR Faculty of Agriculture, University College
if Khartoum
This was the first attempt in the Sudan to investigate the microscopic fungi inhabiting the soil. The Waksman dilution method, Warcup's soil-plate method and Cheaters's immersion-tube technique were used for ten soil samples from the top 6 in. at ten sites. A list of the isolated fungi is given. Few qualitative differences were observed between the species of fungi found in different soils.
Clouston (1935-40) isolated some fungi from roots in the Gezira soil but no other records have been found. It has therefore been imperative to aim first at finding which fungi are present rather than which are the more active in the soil. The Waksman dilution method (1922), as recommended by Brierley (1923), was therefore chiefly used, but the Wareup (1950) and Chesters (1948) techniques were also tried. For Waksman's method, five culture media were used, namely Waksman's, modified Waksman (dextrose, 20 g.; asparagin, 2 g.; MgS0 4 • 7H20, 0'5 g.; FeCla , o· I g.; NaCl, 0'5 g.; and agar 20 g.; distilled water 1000 mI.), Conn's, Czapek-Dox and soil-extract agar, at incubation temperatures varying over the range 29-34 0 C. The fungi that appeared were more or less the same on all media. However, overgrowth of Rhizopus in the first two rendered them less suitable for the dilution method. By comparison, the other three media are less rich, and therefore have proved more suitable, particularly when acidified or used with rose bengal. Acidification of the media to a pH 4'5-5 was found necessary to check the overwhelming growth of bacteria which appeared at pH 5'5 or more. Rose bengal at I: 15,000 was not as effective in its suppression of the bacteria or of Rhizopus as was found by Dawson & Dawson (1947). There was no significant difference, however, between media made up with rose bengal, at I: 15,000 or I: 10,000, and acidified media in the numbers and types of fungi growing on them. Rose bengal considerably limited the growth in diameter of all the fungi, and particularly so at I : 5000. Inoculations of bacteria, R. stolonifer and other fungi were made on all media, for comparison with the findings from soil dilution plates, under the same conditions. The directives in Brierley, Jewson & Brierley (1927) were followed. Soils from ten different sites were sampled from the top 6 in., and their moisture and clay contents were determined. All samples came from heavy sodium-alkaline clay soils from a locality some 7 miles north of Khartoum on the east bank of the Nile, except one less alkaline silt soil from a site near the river bank.
358
Transactions Britisb Mycological Society
The soils in the order examined were: Soil I. Rich in organic debris. The sample was obtained from a plot containing the crowns and roots of cut dura hay (Sorghum vulgare). Collected in August. Clay content 30 %. Moisture content 10'5. Soil II. From same plot as I above, collected 4 weeks later. Clay content 30 %. Moisture content 6·8. Soil III. Same plot as I; collected 12 weeks later. Clay content 30%. Moisture content 6'3. Soil IV. Virgin soil. Vegetation sparse; fairly abundant only during the rainy season (July to September); sample collected in November. Clay content 20 %. Moisture content 3.8. Soil V. Same as IV above, collected in February. Clay content 15 %. Moisture content 3'7. Soil VI. River silt, collected 2 ft. from the edge of the Nile in October, before the typical 'gerf' vegetation had started. Clay content 15 %. Moisture content 18'5. Soil VII. Same as VI above, collected 8 weeks later; 'gerf' vegetation present. Clay content 15 %. Moisture content 4'9. Soil VIII. Under Medicago sativa, collected in July. Clay content 35 %. Moisture content 17'2. Soil IX. Same as VIII above, collected 6 weeks later. Clay content 35 %. Moisture content 10'5. Soil X. Fallow for 6 months succeeding crop of Medicago sativa, collected in June. Clay content 35 %. Moisture content 6.5. Duplicate plates were used for soil dilutions of I: 20,000, I :40,000 and I : 100,000, in order to obtain a suitable dilution for a counting and examination. Counts were made on the third and fourth days. Sporulation occurred in most cases on the third day; complete overcrowding of colonies occurred on the fifth day, and by the eighth day the perithecial state of some Aspergilli, e.g. Aspergillus nidulans, completely replaced the conidial state. The numbers of fungi per gram of soil were consistently too high to be anything but largely a development of colonies from spores. Growth appeared in less than 36 hr. on all media; bacterial growth predominated within 3 days at the natural pH values of the media. Acidification to pH 4'5-5 was therefore necessary, using sulphuric acid with bromocresol green indicator and a 'Lovibond' comparator. The fungi grew well on all media and produced asexual spores on the third day, covering the plates completely by then, where rose bengal was not used. For the Chesters immersion tube and the Warcup soil-plate technique, plain agar (instead of nutrient agar as in Warcup, 1950) was used. Rhizopus stolonifer, Aspergillus nidulans, A. niger, A.flavus, Curvularia lunata, Alternaria tenuis, and Fusarium solani have been the most frequent fungi isolated by these three methods. They have appeared in most soils (see Table I); they were the dominant isolates not only with the Waksman method, where they may have been largely represented by their spores (Conn, 1918; McLennan, 1928), but also when the other two methods with plain agar were used.
359
Sudan soilfungi. M. A. Nour Table
I.
Occurrence
riffungi in samples rif Sudan soil (For details see text)
Name of organism Pythium aphanidermatum (Edson) Fitz, Pythium sp. Absidia blakesleeana Lendn. Rhizopus stolonifer (Ehrenb. ex Fr.) Lind R. arrhieus Fischer (syn, R. nodosus) Mucor hiernalis Wehmer M. circinelloides van Tiegh. Thamnidium (? elegans) Syncephalastrum racemosum (Cohn) Schroet. Helicostylum pyriforme Bain. Aspergillus niger van Tiegh. A. nidulans (Eid.) Wint. A. terreus Thom A. melleus Yukawa A. sydowi (Bain. & Sart.) Thom & Church A.jlavus Link ex Fr. A. versicolor (Vuill.) Tirab. A. flauipes Bain, & Sarto A. tamarii Kita A. nidulans (Eid.) Wint. var.nov. A. candidus Link ex Fr. A.fumigatus Fresen. var.nov, Penicillium funiculosum Thom P. corylophilum Dierckx Paecilomyces uarioti Bain, Gliocladium roseum Bain, Alternaria tenuis Nees Curvularia lunata (Wakker) Boedijn Cladosporium cladosporioides (Fres.) De Vries C. sphaerospermum Penzig Triclwthecium sp. Thielaoia sp, Fusarium solanisensu Snyder & Hansen F. scirpi Lamb. & Fautr, var. compactum Wr. Corticium solani (Prill. & De1acr.) Bourd. & Galz. Total number of species
,
A
I
I
II
III
x
x x
X
x
x x
x x
x x
x
x
IV
V
VI
VII VIII IX
x
x
X x
x
x
x
x
x x x
x
x
x
x
x
x
x
x x x x
x
x
x x x x x x
x x x x x x
x x x x x x
x x x x
x x x
x x x x
x x x x
x x x x x x
x x x
x x x
x x x
x x
x x x
x x
x x
x x
x x
x
x
x
x
x
x x
x x
x
x
x
26
28
29
x x x
x x x
x x
x
x x x x x
x x x x x x
x x x x x x
x x x x x
x x
x x x
x x x
x x x x
x x x
x
x
x x
x
x
x
x
x x x
x x x
x x x x x
x
x
x
x
x
x
x
x
x
21
22
22
x x
x
x x x
x x x x x x x x x X
9
8
8
26
CONCLUSION
The fungi obtained by the different methods are similar in type and in degree of prevalence to those recorded from similar soils in other warm countries (Sabet 1935; Chaudhuri & Sachar, 1934; Todd, 1932; Jensen, 1931; Waksman, 1917; Werkenthin, 1916). Although climate and soil are closely interdependent, it appears that climatic more than edaphic similarities have resulted in this similarity of soil fungal floras. I am grateful to the Director and staff of the Commonwealth Mycological Institute for their help in the identification of the fungi. Voucher
360
Transactions British Mycological Society
cultures are available in the mycological herbaria of the C.M.I. and the Faculty of Agriculture, Khartoum North. I am also grateful to Mr G. A. Worral for assistance in the soil analyses. REFERENCES BRIERLEY, W. B. (1923). The occurrence of fungi in soil. In Russell, E. J., The microorganisms of the soil. London: Longmans, Green & Co. BRIERLEY, W. B.,]EWSON, S. T. & BRIERLEY, M. (1927). The quantitative study of soil fungi. Proc. 1St Int. Congr. Soil Sci. 3, 48-71. CHAUDHURI, H. & SACHAR, G. S. (1934)' A study of the fungus flora of the Punjab soils. Ann mycol., Berl., 22, 90-100. CHESTERS, C. G. C. (1948). A contribution to the study offungi in the soil. Trans. Brit. mycol, Soc. 30, 100-117. CLOUSTON, T. W. (1935-40). Rep. Sudan Res. Div. CONN, H. ]. (19 I 8). The microscopic study of bacteria and fungi in the soil. Tech. Bull. N.r. St. agric. Exp, Sta., no. 64. DAWSON, V. T. & DAWSON, R. C. (1947). Further observations on the use of rose bengal for enumeration of soil fungi. Proc. Soil Sci. Soc. A mer. 1946, 267-269. JENSEN, H. L. (1931). The fungus flora of the soil. Soil Sci. 31, 123-158. McLENNAN, E. (1928). The growth of fungi in soil. Ann appl. Biol. 15, 95-109. SABET, Y. S. (1935). A preliminary study of the Egyptian soil fungi. Bull. Fac. Sci. Egypt. Univ.5, 1-29. TODD, R. L. (1932). Phycomycetes, Ascomycetes and Fungi Imperfecti in Oklahoma soils. Science, 76, 464. WAKSMAN, S. A. (1917). Is there any fungus flora of the soil? Soil Sci. 3, 565-589. WAKSMAN, S. A. (1922). A method for counting the number offungi in the soil. ]. Bact. 7,339-341. WARCUP,]. H. (1950). The soil-plate method for isolation of fungi from soil. Nature, Lond., 166, 117. WERKENTHIN, F. C. (1916). Fungus flora of Texas soils. Phytopathology, 6, 241-253.
(Acceptedfor publication 18 November 1955)