Association between Chrysosporium pannorum and Mucor hiemalis in Poa flabellata litter

Notes and brief articles mycelial cord-forming wood -decay species (P hallus impudicus Pers., Phanerochaete laev is (F r.) Erikss. & Ryv ., Steccherinum fimbriatum (Pers. : Fr.) Er ikss., Tricholomopsis platyphylla (Pers. : Fr.) Sing ., and' fairy -ring ' litter decomposers (Clitocybe fiaccida (Sow.: Fr.) Kummer, Clitocybe nebularis (Barsch : Fr.) Kummer, Marasmius wynnei Berk . & Br.) are capable of forming extensive and persistent systems of luxuriant mycelium (T hompson, 1982; Thompson & Rayner, 1982a ; Mitchell & Rayner, upubl.). Population studies indicate that mycelial types (genotypes) of such fungi can occupy areas of the woodland floor as much as 100 m or more in diameter (Becker , 1953 ; Thompson & Rayner, 1982b; Mitchell & Rayner, unpubl.). The durability of these may be associated with their non-palatability being maintained as a consequence of the lack of deleterious confrontations with other organisms of the same or different species. Clearly the implications of the present observations are numerous and varied, and provide the basis for novel experimental model systems. We thank the Natural Environmental Research Council and the Science and Engineering Research Council for financial support, and Mr Chris Dowson for the photograph of H . serpens.

151 REFERENCES

BECKER, G. (1953). La Vie Priueedes Champignons. Paris : Stock. COATES, D ., RAYNER, A. D. M. & TODD, N . K. (1981). Mating behaviour, mycelial antagonism and the establishment of individuals in Stereum hirsutum,

Transactions of the British Mycological Society 76, 4 1-51. HEALEY, I. N . & RUSSELL-SMITH, A. (1972). Abundance and feeding preferences of fly larvae in two woodland soils. Proceedings of the IVth International Congress of Soil Zoology, Dijon, 1970,177-191. RAYNER, A. D . M . ( 1976). Dematiaceous hyphomycetes and narrow dark lines in decaying wood . Transactions of the British Mycological Society 67, 546-549. RUSSELL-SMITH, A. (1979). A study of fungus flies (Di ptera: Mycetophilidae) in beech woodland. Ecological Entomology 4, 355-364. THOMPSON, W. (1982). Biology and ecology of mycelial cord-forming basidiomycetes in deciduous woodlands. Ph.D. Thesis, University of Bath. THOMPSON, W . & RAYNER, A. D. M. (1982a). Structure and development of mycelial cord systems of Phanerochaete laevis in soil. Transactions of the British Mycological Society 78, 193-200. THOMPSON, W . & RAYNER, A. D. M. (1982b). Spatial structure of a population of Tricholomopsis platyphylla in a woodland site. New Phytologist 92, 103-114. VISSER, S. & WHITTAKER, J. B. (1977) . Feeding preferences for certain litter fungi by Onychiurus subtenuis (Collem bola). Oikos 29, 320-325.

ASSOCIATION BETWEEN CHRYSOSPORIUM PANNORUM AND MUCOR HIEMALIS IN POA FLABELLATA LITTER BY J. L. HURST AND G. J. F. PUGH Department of Biolog ical Sciences, University of Aston in Brimingham, Gosta Green, Birmingham B4 7ET

Mucor hiemalis was frequently isolated from the litter of Poa flabellata where it apparently grows as a secondary sugar fungus in association with Chrysosporium pannorum. Chrysosporium pannorum (Link) Hughes has been reviewed by Carmichael (1962). It appears to be a widespread fungus, with recorded isolations from a variety of habitats and climatic conditions (Williams & Pugh, 1974). The species shows a well-developed ability to grow at low temperatures. Brooks & Hansford (1923) observed slight growth at -6°C, and Poole & Price (1971) stated that growth occurred at 5° on cellulose agar . Ivarson (1973) considered that C. pannorum was an important decomposer of leaf litter at low temperatures, and Hurst (1982) showed in vitro activity of Cx cellulase from C. pannorum at 1°. Hurst

(1982) working with sub-Antarctic isolates, and Kuthubutheen (1977) with English isolates, both found the fungus to have an upper temperature limit to growth of 28°, and an optimum temperature for growth of 18°. During a study of microfungi present on leaves and litter on the sub-Antarctic island of South Georgia (54°- 55° S, 36°-38° W), C. pannorum was frequently isolated in conjunction with Mucor hiemalis Wehmer from litter of the tussock grass , Poa fiabellata (Lam .) Hook.f. The litter of this grass normally accumulates at the bases of tussocks, where it may remain for some years prior to

Trans. Br. mycol. Soc. 81 (1), (1983). Printed in Great Britain

Notes and brief articles Table 1. Soluble carbohydrate content of Poa flabellata leaf classesfrom GLC analysis of 80 % ethanol extracts Carbohydrate Arabitol Fructose a-Glucose .a-Glucose Mannitol Sucrose Trehalose Total

Standing dead leaves

New leaves 0'00 11'60 ±5 '64 6-0<} ± 3-14 10'38 ±5'07 0-00 14'42 ±7-49 o'86 ±0'73

0'78 ± 0'40 l 'oo± 1'41 0-71 ± 1'00 0-89±1 '25 0'18 ±O'25 0'89±1 '25 2'31 ±2'06 6-74±7' 63

43'58±20'98

Litter 0-00 0-26±0-27 0 '13 ±0-13 o '4 2±0 '3 0 0'00 0-33±0'26 not tested 1'45±0-9 1

Values as flg rng" dry weight j s.n,

complete degradation (Smith & Walton, (975). The soluble carbohydrate content of the litter is relatively low when compared with new and standing dead leaves (Table 1), and the carbon :nitrogen ratio is usually between 40:1 and 60 : 1 (D. W. H. Walton, pers. comm.). M. hiemalis was unable to grow well in autoclaved litter at 5 or 20° in vitro following inoculation from a spore suspension, whilst C. pannorum grew to sporulation within 20 days from inoculation of the litter. Introduction of both C. pannorum and M. hiemalis to sterile litter allowed readily visible, although not prolific growth of the latter species. A similar situation has been observed on cellulose agar, where this isolate of Mucor hiemalis showed only very sparse growth prior to the introduction and growth of C. pannorum. On malt extract agar an interaction was often observed between colonies of the two species, such that the normal low powdery growth of C. pannorum was altered to a floccose growth up to 1 em in height. Overgrowth of Chrysosporium by Mucor also occurred. No hyphal lysis or other interaction has been observed in either colony. It is probable that in this situation, M . hiemalis is exploiting a microhabitat on a substrate upon which it cannot thrive alone. By growing in conjunction with C. pannorum, M . hiemalis is utilising soluble carbohydrate products resulting from cellulase activity of the Chrysosporium, and thereby taking the role of a 'secondary sugar fungus' as defined by Garrett (1963) and Hudson (1968). A similar role for M . hiemalis has been suggested by Frankland (1969) in fungal successions on bracken. Tribe (1966) showed a comparable phenomenon with Pythium oligandrum, which was able to grow on cellophane films in association with Trans. Br , mycol. Soc- 81 (1), (1983).

the cellulose-decomposing Botryotrichum piluliferum and Fusarium culmorum. Inoculation of M. hiemalis spores into colonies of C. pannorum on leaf litter in vitro has shown no significant increase in the rate of litter decomposition, but studies of the repression of production of cellulases by C. pannorum at high glucose levels may be rewarding. This study highlights the potential importance of dual or multiculture systems in ecological studies of this type . This work was supported by a grant from the Natural Environment Research Council, and was undertaken with the help of the British Antarctic Survey. REFERENCES

BROOKS, F . T . & HANSFORD, C. G. (1923). Mould growth upon cold stored meat . Transactions of the British Mycological Society 8, 113-141. CARM1CHAEL,J . W. (1962). Chrysosporiumand some other aleuriosporic hyphomycetes. Canadian Journal of Botany 40, 1137-1173. ' FRANKLAND, J. C. (1969). Fungal decomposition of bracken petioles . Journal of Ecology 57, 27-3 6. GARRETT, S. D . (1963). Soil Fungi and Soil Fertility. Oxford : Pergamon Press. HUDSON, H . J. (1968). The ecology of fungi on plant remains above the soil. New Phytologist 67,837-874, HURST, J, L. (1982). Biology of fungi on plants in the Sub-Antarctic. Ph .D. Thesis, University of Aston in Birmingham. IVARSON, K . C. (1973). Fungal flora and rate of decomposition of leaf litter at low temperatures. Canadian Journal of Soil Science 53, 79-84. KUTHUBUTHEEN, A. J. (1977 ). The effects of fungicides on soil and leaf fungi , Ph .D. Thesis, University of Aston in Birmingham.

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Notes and brief articles POOLE, N. J. & PRICE, P. C. (1971). The occurrence of Chrysosporium pannorum in soilsreceiving incremental cellulose. Soil Biology and Biochemistry 3, 161-166. SMITH, R. I. L. & WALTON, D. W. H. (1975). South Georgia, Sub-Antarctic. In Structure and Function of Tundra Ecosystems (ed. T. Rosswall & O. W. Heal), Ecological Bulletins (Stockholm)

20, 39~423.

153

TRIBE, H. T. (1966). Interactionsofsoilfungion cellulose film. Transactions of the British Mycological Society 49, 457-466. WILLIAMS, J. I. & PuGH, G. J. F. (1974). Fungal Biological Flora: Chrysosporium pannorum (Link) Hughes. International Biodeterioration Bulletin 10, 75-80 .

INFLUENCE OF A VOLATILE COMPOUND ON FORMATION OF VESICULAR-ARBUSCULAR MYCORRHIZAS BY T. V. ST. JOHN, R. I. HAYS AND C. P. P. REID

Natural Resource Ecology Laboratory and Forest and Wood Sciences, Colorado State University, Fort Collins, CO 8°523, U.S.A. Suppression of VAM infection in the presence of potassium permanganate indicates that an easily oxidizable compound(s) have a largely stimulatory effect on VAM infection. The effects of volatile compounds on soil microorganisms have received considerable attention (Linderman & Gilbert, 1975; Primrose, 1979; Stotzky & Schenck, 1976). Vancura & Stotzky (1976) have studied some of the many kinds of volatile compounds that can be produced by germinating seeds and seedlings and Koske (1982) has shown that an unidentified volatile compound is involved in the location of plant roots by Gigaspora gigantea germ-tubes. During attempts to establish pure twomembered vesicular-arbuscular mycorrhizal (VAM) infections, we hypothesized that an unidentified volatile compound influences the infection process and suggested that accumulation of an inhibitory volatile produced by plant, fungus, or components of the container assembly was responsible for difficulties in establishing gnotobiotic VAM cultures (St. John, Hays & Reid, 1981). We attributed our success to the container design, which allowed free circulation of air. In this paper we report an experiment designed to directly test for an active role of a volatile compound in VAM infection. The experiment was carried out in two sterile plastic isolators (' sterile tents '), illuminated by separate banks of plant growth lights. Quantum flux density at plant height was 110-120 p,E m ? S-1 inside the isolators. Day length waS15'5 hand room temperature 26'5 ± 1°C. Sterile clover (Trifolium repens L.) seedlings were planted in sand in glass funnels fitted with glass wool wicks and inoculated with two surfacesterilized spores of Gigaspora margarita Becker & Hall per plant. Each funnel rested in a 250 ml Trans. Br. mycol. Soc. 81 (1), (1983).

beaker containing 150 ml of nutrient solution (St. John, Hays & Reid, 1981). Each beaker-funnel unit was in turn placed inside a 1000 ml Berzelius beaker. In half of the units a 35 mm uncovered, sterile plastic Petri dish containing 2 g of silica gel impregnated with potassium permanganate was placed in each container. Permanganate is a strong oxidant of a wide range of organic compounds (Stewart, 1965) including hydrocarbons such as ethylene. Each small Petri dish was fixed to a glass microscope slide with silicon stopcock grease, and the slide placed on the edge of the funnel. The control treatment was identical except that the silica gel was not impregnated with potassium permanganate. Seven units of each treatment were placed in isolator 1 and 10 control and 11 treatment units in isolator 2. They were maintained for 34 days, during which time moisture was replenished as required by pouring sterile deionized water into the sand-filled funnel. At harvest a small quantity of sand from each funnel was plated on 'Difco' nutrient agar to check sterility. By harvest date all units had bacterial contaminants. Shoot weight of each plant was determined after oven-drying. Roots from each unit were cleared and stained (Phillips & Hayman, 1970) and length of infected root determined by a line - intercept technique (Marsh, 1971). Any portion of a root containing arbuscules or internal hyphae was considered infected. Analysis of variance showed that shoot weights did not differ significantly between the two plastic isolators or between treatments. Mean length of infected root is shown in

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