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Dead basil stems — a possible ecological niche for the hoar-frost fungus
Volume 15, Part 4, November 2001
Dead basil stems - a possible ecological niche for the hoar-frost fungus
Botryosporium longibrachiatum HENRY T. TRIBE l AND ROLAND W. S. WEBER2 lWolfson College, Cambridge CB3 9BB, UK. "Lehrbereich. Biotechnologie, Unioersitiii Kaiserslautern, Paul-Ehrlich-Str. 23, 67663 Kaiserslautern, Germany. E-mail [email protected]
In the summer of 1997, HTT found that the lower, dead parts of some plants of basil (Ocimum basilicum) appeared very much as if covered with hoar-frost. The plants, which had been bought from a supermarket as pots of seedlings, had been partially used for culinary purposes but then left on a window-sill and neglected such that they had dried out and died. The 'needles' of 'hoar-frost' were found to be the long conidiophores of Botryosporium longibrachiatum (Oudemans 1890) Maire 1903 (Figs 1, 2 and 5). This spectacular fungus has been recovered from similarly maltreated basil plants in each subsequent year, which leads us to believe that recently dead basil tissue in the proximity of the potting soil used for commercial propagation represents an ecological niche in which this fungus develops regularly. An excellent paper on the genus Botryosporium Corda 1839 was published by Zhang & Kendrick (1990) who treated the four known species, redescribing and illustrating B. longibrachiatum. This species differs from the type, B. pulchrum Corda 1839, in several ways, notably in that its conidiophore is unbranched, whereas dichotomous branching is characteristic of B. pulchrum. Zhang & Kendrick pointed out that the photomicrographs ascribed to B. longibrachiatum in Barron (1968) are, in fact, those of B. pulchrum. Barron's material came from particles on the surface of potting soil in the greenhouse. Further, we may note that a beautiful fungus identified as B. pulchrum was observed in Alnwich Park during the BMS autumn foray of 1906, 'over-running decaying vegetation with a delicate frost-like coating' (Smith & Rea, 1907). These authors described their fungus 'with upright conidiophores about
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1/4 inch in height. The main axis gives rise to a succession of secondary branches in acropetal succession which are short and divide near their tips to form four or five semi-globose heads ... '. Nothing is noted on dichotomous branching, and it is very possible that in fact they were observing B. longibrachiatum. Botryosporium longibrachiatum was first found on the upper surfaces of leaves, mainly those which had dried out, of Curcuma rubricaulis in the Amsterdam Botanic Garden (Oudemans, 1890). Early authors found it on a wide variety of dead plant material, e.g. Maire in 1900 on a dead stem of Pogostemoti patchouly, Kellerman in 1903 on dead herbaceous stems in an Ohio greenhouse, and Bainier in 1910 on dead leaves of banana. Ellis & Ellis (1997) have classed it as a plurivorous fungus on (dead) herbaceous plants. They cited its occurrence on dead stems and leaves of 'Dahlia, Dianthus, Lycopersicon, Solanum, etc.', and subsequently (Ellis & Ellis, 1998) noted that it had been found several times on twine used to support tomato plants in greenhouses. Kendrick found it on leaves of Papaver in his garden at Waterloo, Ontario, and H.T. saw it once on dead tissue at the base of the Purple Heart house plant, Setcreasea purpurea. In order to test the ability of B. longibrachiatum to infect dead plant material de novo, we inoculated dried stems of basil and several other culinary herbs, viz chives (Allium schoenoprasum), lemon balm (Melissa officinalis), lovage (Levisticum officinale), marjoram (Origanum vulgare), parsley (Petroselinum crispum), sage (Salvia officinalis), tarragon (Artemisia dracunculus) and thyme (Thymus vulgaris), with a conidium suspension and then
Volume 15, Part 4, November 2001
Fig 1 Conidiophore of Botryosporium longibrachiatum prepared from an infected basil stem and mounte d as described in the text . Th e tip of the conidiophore is formin g num erous lateral branches which produce a swollen tip (vesicle). From eac h vesicle, several lobed am pullae ar ise which sub sequ entl y prod uce conidia. Bar = 100 [.L m . Fig 2 A frill of conidiophores arising from a dried colonized basil stem 48 h after placing it in a damp- chamber. Bar = 2 mm. Fig 3 Successive stages of conidiogenesis on ampullae from adjacent lateral branches. From an initially smooth surface (top), numerous denticles are produced (centr e), each of which expands a conidium (bottom). Also note th e very narrow points of attachment of the ampullae to the vesicles. Bar = 20 [.Lm. Fig 4 Nearly mature elongated egg-shape d conidia still attached to the denticles. Bar = 20 urn.
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Volume 15, Part 4, November 2001 Once plant stems with conidiophores of B. longibrachiatum have been obtained, they can be dried and stored dryas herbarium material for some months. Within 1-2 days of placing the dry material on moist tissue paper, a fresh crop of conidiophores is produced. The fungus is readily isolated into pure culture and displays good growth and sporulation on a range of agar media such as potato dextrose agar, oatmeal agar, 2% malt extract agar or cornmeal agar. For production of very large conidiophores, we recommend yeast extract-sucrose (YES) agar, containing 4 g yeast extract, 20 g sucrose, 1 g KH 2P0 4, 0.5 g MgS04·7H 20 and 15-20g agar per litre of tap water. Within a few days' incubation at r.t., abundant and strikingly beautiful conidiophores (up to 5 mm long) are produced (Fig 6). These are much larger than the ones produced on plant stems which are usually less than 2 mm in length (Figs 1 and 2). The fungus sporulates profusely in diffuse daylight as well as in the dark. The agar Fig 5 Typical occurrence of B. longibrachiatum on the dead stems and leaves of potted colonies, which are initially basil plants. Fig 6 B. longibrachiatum on YES agar after 5 days' incubation at room white, acquire a light salmon temperature. Note the dense tufts of very long conidiophores. Bar = 10 mm. colour after four weeks. incubated the samples in damp-chambers at Upon closer inspection, the conidiophore of B. room temperature. Within 3 days, typical longibrachiatum follows a regular pattern in which conidiophores (Fig 2) were observed on all the main axis produces lateral branches, each samples except lovage and parsley. In contrast, terminating in a swollen vesicle (Fig 1) which in no infections could be established on living turn gives rise to several lobed ampullae (Figs 3 healthy or wounded basil plants even after and 4). Detailed light microscopy observations of repeated heavy inoculation, indicating that B. these ampullae are rewarding because they reveal longibrachiatum is purely a saprotroph and has a splendid example of synchronous polyblastic no capacity to cause disease. We have, however, conidiogenesis, i.e. numerous conidia are observed it as a secondary infection in moribund produced simultanously at the tips of small regions of basil plants succumbing to Pythium denticles scattered over the entire distal surface damping-off or to the grey mould Botrytis cinerea of an ampulla whereby adjacent ampullae may Persoon 1801. show successive stages of conidium formation
Volume 15, Part 4, November 2001 (Figs 3 and 4). This type of conidium formation is also found e.g. in the genus Botrytis (Hughes, 1953). In order to obtain good material for microscopy, conidiophores should first be immersed in 70% ethanol in order to wash off the mature spores which otherwise obscure the features of interest. Material should then be transferred to a small volume of lactic acid in a watch-glass, from which individual conidiophores can be removed with a very fine needle for mounting in lactic acid on a microscope slide. It will be interesting to discover whether the fmding of B. longibrachiatum in the 'basil niche' is a general occurrence, because this has proved to us a very simple procedure for obtaining a fairly unusual and strikingly beautiful hyphomycete. We have not seen B. pulchrum. However, when Botryosporium species occur in natural vegetation they can be most striking. Bramley (1985), commenting about B. pulchrum on Urtica, noted that at Kingthorpe, Pickering, in October 1945, E. W. Mason remarked that 'over a hundred yards, the clouds of its conidia marked the track of every forayer'. Bramley did not include B. longibrachiatum in his fungus flora of Yorkshire.
Acknowledgement We thank Mrs. Renate Emser for providing liberal quantities of herbs for our inoculation experiments, and Mr. Philip Oswald for translating Oudemans's Latin. References Barron, G. L. (1968). Genera of Hyphomycetes from Soil. Williams and Wilkins: Baltimore. Bramley, W. G. (1985). The Fungus Flora of Yorkshire. Mycological Section, Yorkshire Naturalists' Union. Ellis, M. B. & Ellis, J. P. (1997). Microfungi on Land Plants (enlarged edition). Richmond Publishing: Slough. Ellis, M. B. & Ellis, J. P. (1998). Microfungi on Miscellaneous Substrates (enlarged edition). Richmond Publishing: Slough. Hughes, S. J. (1953). Conidiophores, conidia, and classification. Canadian Journal of Botany 31: 577-659. Oudemans, C. A. J. A. (1890). Micromycetes nouveaux. Verslagen en Mededeelingen der Koninklijke Akademie van Wetenschappen, Afdeeling Natuurkunde 3.7: 312327. Smith, A. L. & Rea, C. (1907). New and rare British fungi. Transactions of the British Mycological Society 3: 35. Zhang, T. & Kendrick, B. (1990). A reassessment of Botryosporium (Hyphomycetes). Acta Mycologica Sinica 9: 31-40.
British Mycological Society Publications Recent additions to the Society's list of Miscellaneous Publications are included here. All items are obtainable from the BMS Librarian, c/o The Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE. Prices do not include delivery - see below for postage costs. Guide to the Literature for the Identification of British Basidiomycetes. By Bert Brand, Alick Henrici & Patrick Leonard (2001). A completely new version of the earlier Guide, which was last produced by Margaret Holden in 1982. Price: £5.00 A Checklist of the Rust Fungi of the British Isles. By D. M. Henderson (2000). The revision and update of the earlier work by Wilson & Henderson. Price: £4.00 A Census Catalogue of the Myxomycetes of Great Britain and Ireland. By Bruce lng. Second edition (2000); 20pp, including Notes and Bibliography. Price: £2.00 Keys to Fungi on Dung. By M. J. Richardson & Roy Watling (1997). 68pp. Provides keys to the Ascomycetes, Basidiomycetes and Mucorales occurring on dung and associated debris. Price: £6.00 British County Foray Lists. Compiled by G. C. Ainsworth & Grace Waterhouse (1989). References to lists of fungi in the British Isles. Price: £3.00 Keys to the species of Russula. By R. W Rayner. 3rd Edition, 1985 Price: £5.00 Key to the Gasteromycetes of Great Britain. By V Demoulin & J. V R. Marriott (1981). Price: £2.00 For each of the above publications, add to the stated price 50p for postage within the UK or £1.00 for destinations within Europe; or £1.50 elsewhere.
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Dead basil stems - a possible ecological niche for the hoar-frost fungus
Botryosporium longibrachiatum HENRY T. TRIBE l AND ROLAND W. S. WEBER2 lWolfson College, Cambridge CB3 9BB, UK. "Lehrbereich. Biotechnologie, Unioersitiii Kaiserslautern, Paul-Ehrlich-Str. 23, 67663 Kaiserslautern, Germany. E-mail [email protected]
In the summer of 1997, HTT found that the lower, dead parts of some plants of basil (Ocimum basilicum) appeared very much as if covered with hoar-frost. The plants, which had been bought from a supermarket as pots of seedlings, had been partially used for culinary purposes but then left on a window-sill and neglected such that they had dried out and died. The 'needles' of 'hoar-frost' were found to be the long conidiophores of Botryosporium longibrachiatum (Oudemans 1890) Maire 1903 (Figs 1, 2 and 5). This spectacular fungus has been recovered from similarly maltreated basil plants in each subsequent year, which leads us to believe that recently dead basil tissue in the proximity of the potting soil used for commercial propagation represents an ecological niche in which this fungus develops regularly. An excellent paper on the genus Botryosporium Corda 1839 was published by Zhang & Kendrick (1990) who treated the four known species, redescribing and illustrating B. longibrachiatum. This species differs from the type, B. pulchrum Corda 1839, in several ways, notably in that its conidiophore is unbranched, whereas dichotomous branching is characteristic of B. pulchrum. Zhang & Kendrick pointed out that the photomicrographs ascribed to B. longibrachiatum in Barron (1968) are, in fact, those of B. pulchrum. Barron's material came from particles on the surface of potting soil in the greenhouse. Further, we may note that a beautiful fungus identified as B. pulchrum was observed in Alnwich Park during the BMS autumn foray of 1906, 'over-running decaying vegetation with a delicate frost-like coating' (Smith & Rea, 1907). These authors described their fungus 'with upright conidiophores about
•
1/4 inch in height. The main axis gives rise to a succession of secondary branches in acropetal succession which are short and divide near their tips to form four or five semi-globose heads ... '. Nothing is noted on dichotomous branching, and it is very possible that in fact they were observing B. longibrachiatum. Botryosporium longibrachiatum was first found on the upper surfaces of leaves, mainly those which had dried out, of Curcuma rubricaulis in the Amsterdam Botanic Garden (Oudemans, 1890). Early authors found it on a wide variety of dead plant material, e.g. Maire in 1900 on a dead stem of Pogostemoti patchouly, Kellerman in 1903 on dead herbaceous stems in an Ohio greenhouse, and Bainier in 1910 on dead leaves of banana. Ellis & Ellis (1997) have classed it as a plurivorous fungus on (dead) herbaceous plants. They cited its occurrence on dead stems and leaves of 'Dahlia, Dianthus, Lycopersicon, Solanum, etc.', and subsequently (Ellis & Ellis, 1998) noted that it had been found several times on twine used to support tomato plants in greenhouses. Kendrick found it on leaves of Papaver in his garden at Waterloo, Ontario, and H.T. saw it once on dead tissue at the base of the Purple Heart house plant, Setcreasea purpurea. In order to test the ability of B. longibrachiatum to infect dead plant material de novo, we inoculated dried stems of basil and several other culinary herbs, viz chives (Allium schoenoprasum), lemon balm (Melissa officinalis), lovage (Levisticum officinale), marjoram (Origanum vulgare), parsley (Petroselinum crispum), sage (Salvia officinalis), tarragon (Artemisia dracunculus) and thyme (Thymus vulgaris), with a conidium suspension and then
Volume 15, Part 4, November 2001
Fig 1 Conidiophore of Botryosporium longibrachiatum prepared from an infected basil stem and mounte d as described in the text . Th e tip of the conidiophore is formin g num erous lateral branches which produce a swollen tip (vesicle). From eac h vesicle, several lobed am pullae ar ise which sub sequ entl y prod uce conidia. Bar = 100 [.L m . Fig 2 A frill of conidiophores arising from a dried colonized basil stem 48 h after placing it in a damp- chamber. Bar = 2 mm. Fig 3 Successive stages of conidiogenesis on ampullae from adjacent lateral branches. From an initially smooth surface (top), numerous denticles are produced (centr e), each of which expands a conidium (bottom). Also note th e very narrow points of attachment of the ampullae to the vesicles. Bar = 20 [.Lm. Fig 4 Nearly mature elongated egg-shape d conidia still attached to the denticles. Bar = 20 urn.
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Volume 15, Part 4, November 2001 Once plant stems with conidiophores of B. longibrachiatum have been obtained, they can be dried and stored dryas herbarium material for some months. Within 1-2 days of placing the dry material on moist tissue paper, a fresh crop of conidiophores is produced. The fungus is readily isolated into pure culture and displays good growth and sporulation on a range of agar media such as potato dextrose agar, oatmeal agar, 2% malt extract agar or cornmeal agar. For production of very large conidiophores, we recommend yeast extract-sucrose (YES) agar, containing 4 g yeast extract, 20 g sucrose, 1 g KH 2P0 4, 0.5 g MgS04·7H 20 and 15-20g agar per litre of tap water. Within a few days' incubation at r.t., abundant and strikingly beautiful conidiophores (up to 5 mm long) are produced (Fig 6). These are much larger than the ones produced on plant stems which are usually less than 2 mm in length (Figs 1 and 2). The fungus sporulates profusely in diffuse daylight as well as in the dark. The agar Fig 5 Typical occurrence of B. longibrachiatum on the dead stems and leaves of potted colonies, which are initially basil plants. Fig 6 B. longibrachiatum on YES agar after 5 days' incubation at room white, acquire a light salmon temperature. Note the dense tufts of very long conidiophores. Bar = 10 mm. colour after four weeks. incubated the samples in damp-chambers at Upon closer inspection, the conidiophore of B. room temperature. Within 3 days, typical longibrachiatum follows a regular pattern in which conidiophores (Fig 2) were observed on all the main axis produces lateral branches, each samples except lovage and parsley. In contrast, terminating in a swollen vesicle (Fig 1) which in no infections could be established on living turn gives rise to several lobed ampullae (Figs 3 healthy or wounded basil plants even after and 4). Detailed light microscopy observations of repeated heavy inoculation, indicating that B. these ampullae are rewarding because they reveal longibrachiatum is purely a saprotroph and has a splendid example of synchronous polyblastic no capacity to cause disease. We have, however, conidiogenesis, i.e. numerous conidia are observed it as a secondary infection in moribund produced simultanously at the tips of small regions of basil plants succumbing to Pythium denticles scattered over the entire distal surface damping-off or to the grey mould Botrytis cinerea of an ampulla whereby adjacent ampullae may Persoon 1801. show successive stages of conidium formation
Volume 15, Part 4, November 2001 (Figs 3 and 4). This type of conidium formation is also found e.g. in the genus Botrytis (Hughes, 1953). In order to obtain good material for microscopy, conidiophores should first be immersed in 70% ethanol in order to wash off the mature spores which otherwise obscure the features of interest. Material should then be transferred to a small volume of lactic acid in a watch-glass, from which individual conidiophores can be removed with a very fine needle for mounting in lactic acid on a microscope slide. It will be interesting to discover whether the fmding of B. longibrachiatum in the 'basil niche' is a general occurrence, because this has proved to us a very simple procedure for obtaining a fairly unusual and strikingly beautiful hyphomycete. We have not seen B. pulchrum. However, when Botryosporium species occur in natural vegetation they can be most striking. Bramley (1985), commenting about B. pulchrum on Urtica, noted that at Kingthorpe, Pickering, in October 1945, E. W. Mason remarked that 'over a hundred yards, the clouds of its conidia marked the track of every forayer'. Bramley did not include B. longibrachiatum in his fungus flora of Yorkshire.
Acknowledgement We thank Mrs. Renate Emser for providing liberal quantities of herbs for our inoculation experiments, and Mr. Philip Oswald for translating Oudemans's Latin. References Barron, G. L. (1968). Genera of Hyphomycetes from Soil. Williams and Wilkins: Baltimore. Bramley, W. G. (1985). The Fungus Flora of Yorkshire. Mycological Section, Yorkshire Naturalists' Union. Ellis, M. B. & Ellis, J. P. (1997). Microfungi on Land Plants (enlarged edition). Richmond Publishing: Slough. Ellis, M. B. & Ellis, J. P. (1998). Microfungi on Miscellaneous Substrates (enlarged edition). Richmond Publishing: Slough. Hughes, S. J. (1953). Conidiophores, conidia, and classification. Canadian Journal of Botany 31: 577-659. Oudemans, C. A. J. A. (1890). Micromycetes nouveaux. Verslagen en Mededeelingen der Koninklijke Akademie van Wetenschappen, Afdeeling Natuurkunde 3.7: 312327. Smith, A. L. & Rea, C. (1907). New and rare British fungi. Transactions of the British Mycological Society 3: 35. Zhang, T. & Kendrick, B. (1990). A reassessment of Botryosporium (Hyphomycetes). Acta Mycologica Sinica 9: 31-40.
British Mycological Society Publications Recent additions to the Society's list of Miscellaneous Publications are included here. All items are obtainable from the BMS Librarian, c/o The Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE. Prices do not include delivery - see below for postage costs. Guide to the Literature for the Identification of British Basidiomycetes. By Bert Brand, Alick Henrici & Patrick Leonard (2001). A completely new version of the earlier Guide, which was last produced by Margaret Holden in 1982. Price: £5.00 A Checklist of the Rust Fungi of the British Isles. By D. M. Henderson (2000). The revision and update of the earlier work by Wilson & Henderson. Price: £4.00 A Census Catalogue of the Myxomycetes of Great Britain and Ireland. By Bruce lng. Second edition (2000); 20pp, including Notes and Bibliography. Price: £2.00 Keys to Fungi on Dung. By M. J. Richardson & Roy Watling (1997). 68pp. Provides keys to the Ascomycetes, Basidiomycetes and Mucorales occurring on dung and associated debris. Price: £6.00 British County Foray Lists. Compiled by G. C. Ainsworth & Grace Waterhouse (1989). References to lists of fungi in the British Isles. Price: £3.00 Keys to the species of Russula. By R. W Rayner. 3rd Edition, 1985 Price: £5.00 Key to the Gasteromycetes of Great Britain. By V Demoulin & J. V R. Marriott (1981). Price: £2.00 For each of the above publications, add to the stated price 50p for postage within the UK or £1.00 for destinations within Europe; or £1.50 elsewhere.
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