Hyphal interference by Peniophora gigantea against Heterobasidion annosum

Notes and Brief Articles

307

produced by thin-walled 'pro-RS' thalli in earlier studies of the RS strain (Horenstein & Cantino, 1961). Thus, there is no reason to change our view of the taxonomic status of B. britannica. At the same time, one aspect of the morphological variability of populations derived from aged TW plants was described in some detail because this had not been documen ted previously (Horenstein & Cantino, 1961). We do not yet know to what extent, if any, such phenotypic variation resides in differences among the zoospores themselves and how much of it arises as ontogeny progresses. As in B. emersonii (Cantino, 1969; Cantino & Hyatt, 1953), this intriguing question remains essentially unanswered. REFERENCES

CANTI:'W, E. C. (195 I). Metabolism and morphogensis in a new Blastocladiella. Antonie van Leeuwenhoek 17, 325-362. CANTINO, E. C. (1969). Physiological age and germinability of resistant sporangia of Blastocladiella emersonii. Trans. Br. mycol. Soc. 53, 463-467. CANTI~O, E. C. & HYATT, M. T. (1953). Phenotypic 'sex' determination in the life history of a new species of Blastocladiella, B. emersonii. Antonie van Leeuwenhoek 19, 25-7 0 . CANTINO, E. C., TRUESDELL, L. C. & SHAW, D. S. (1968). Life history of the motile spore of Blastocladiella emersonii: a study in cell differentiation. ]. Elisha Mitchell scient. Soc. 84, 125-146. HORENSTEI~, E. A. & CA:IlTDIO, E. C. (1961). Morphogenesis in and the effeet of light on Blastocladiella britannica sp.nov. Trans. Br. mycol. Soc. 44, 185-198. HOREl';"STEI:Il, E. A. & CA~TI:IlO, E. C. (1962). Dark-induced morphogenesis in synchronized cultures of Blastocladiella britannica. ]. Bact. 84, 37-45. HORE:IlSTEIN, E. A. & CANTINO, E. C. (1964)' An effect oflight on glucose uptake by the fungus Blastocladiella britannica. ]. gen. Microbiol. 37, 59-65. HORGE:-l, P. A. & GRIFFI:-l, D. H. (1969). Structure and germination of Blastocladiella emersonii resistant sporangia. Am. ]. Bot. 56, 22-25.

HYPHAL I~TERFERENCE BY PENIOPHORA GIGANTEA AGAINST HETEROBASIDION ANNOSUM F. E. O. IKEDIUGWU, C.

DE~NIS

AND

J.

WEBSTER

Botany Department, University of SheJlield Rishbeth (1950) reported that Heterobasidion annosum (Fr.) Bref. (Fornes annosus (Fr.) Cooke), the causal fungus of butt-rot disease of pines, may be replaced under natural conditions and on artificially inoculated root lengths by Peniophora gigantea. He later reported (1952, 1961, 1963) how artificial inoculation of pine stumps by oidia of P. gigantea could bring about considerable reduction ofcolonization ofpinc stumps by H. annosum, and thus contribute to the control of the disease. There is evidence (Meredith, 1960) that P. gigantea can effectively replace H. annosum as a colonist of pine stumps and it is of interest to examine the interaction betwecn these two fungi. Observations were made using a culture of H. annosum derived from a sporophore collected on a pine stump from Trans. Br. mycol. Soc. 54 (2), (1970). Printed in Great Britain 20-2

308

Transactions British Mycological Society

Sherwood Forest, Clumber Park, near Worksop, Notts. and a strain of P. gigantea (Isolate 9) kindly supplied by Dr Rishbeth. When inocula of the two fungi were placed on opposite sides of a 2 % malt extract agar plate at 25°C, and the colonies allowed to grow towards each other, there was no evidence of a reduction of the growth rate of the Heterobasidion hyphae as the colonies approached each other. This observation suggests that there is no readily diffusible antagonistic factor secreted in advance of the Peniophora hyphae causing inhibition of growth of the Heterobasidion hyphae. This was confirmed by use of the cellophane technique of Gibbs (Ig67a). Plates of z % malt extract agar were covered with a layer of boiled sterilized cellophane 50 flm thick, and the centre of each plate inoculated with a 6 mm disk cut from the margin of a rapidly growing culture plate of Peniophora. The cultures were allowed to grow for 2 and 5 days, then the cellophane carefully removed. The agar surface was re-inoculated with a disk of Heterobasidion inoculum. The growth of the Heterobosidion colonies was compared with controls inoculated directly on to malt extract agar. The control plates and those previously inoculated with Peniophora were incubated at about 22° in the light. No inhibition was detected in the plates previously inoculated with Peniophora. These results confirm those of Gibbs (1967 b). This suggests that if Peniophora affects the growth of Heterobasidion by means of a secretion, this is not diffusible through a cellophane membrane in sufficient concentration to affect the growth rate of the Heietobasidion hyphae. Peniophora gigantea was therefore examined for the ability to show hyphal interference, a mode of antagonism described in Coprinus heptemerus and a number of other coprophilous basidiomycetes by Ikediugwu & Webster (I970a, b). H. annosum and P. gigantea were opposed on a cellophane membrane placed on 2 % malt extract agar in Petri dishes and incubated at 25°. After the two colonies met the zone of contact was examined with a microscope. Cells of H. annosum in contact with the hyphae of P. gigantea were killed (Plate 26, fig. I). Granulation of cytoplasm and vacuolation are followed by loss of opacity of the affected cells. Affected cells take up neutral red, in contrast with the unaffected ones, indicating alteration in the permeability of the former. The flow of cell contents of the sensitive fungus to the point of contact of the cell with a hypha of P. gigantea (Plate 26, fig. 2) suggests that the fall in hydrostatic pressure associated with the hyphal interference is greatest at the point of contact. The hyphal interference of P. gigantea against H. annosum occurs within the range of temperature 5-30°, tested, its effect being limited in all cases to the contacted cells. Although the interference effect of P. giganiea is not exerted on H. annosum through a cellophane membrane, 50 /,lm in thickness, Ascobolus crenulaius overlaid with a cellophane strip of the antagonist shows symptoms of the interference. It appears that the interference factor is diffusible through cellophane and that H. annosum is less sensitive to it than A. crenulatus. It must be noted in addition that the growth of P. gigantea on malt extract lowers the pH of the medium to a level inhibitory to the growth of Trans. Br. mycol, Soc. 54: (2), (1970). Printed in Great Britain

Vol. 54. Plate 26

Trans. Br. myco!. Soc

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Notes and Brief Articles

309

A. crenulatus and that this might have contributed to the observed effects of the antagonist through the cellophane membrane. The antagonism shown by P. gigantea against H. annosum in both natural and artificial situations is possibly effected by means of hyphal interference. We are indebted to Dr ]. Rishbeth for generously making available a culture of P. gigantea and for helpful discussion. REFERE~CES

GIBBS, j. N. F. (1967a). A study of the epiphytic growth habit of Fornes annosus. Ann. Bot.

N.S. 3 1, 755-744. GIBBS,j. N. F. (1967b). The role of host vigour in the susceptibility of Pines to Fornes

annosus. Ann. Bot. N.S. 31,803--815. IKEDlUGWU, F. E. O. & WEBSTER,j. (1970a). Antagonism between Coprinus heptemerus and other coprophilous fungi. Trans. Br. mycol. Soc. 54, 181-204. IKEDlUGWU, F. E. O. & WEBSTER,j. (1970b). Hyphal interference in a range of coprophilous fungi. Trans. Br. mycol. Soc. 54, 205-210. MEREDITH, D. S. (1960). Further observations on fungi inhabiting Pine stumps. Ann.

Bot. 24, 63-78. RIsHBETH,j. (1950). Observations on the biology of Fornes annosus, with particular reference to East Anglian pine plantations. I. The outbreak of the disease and ecological status of the fungus. Ann. Bot. ~.S. :14, 365~-383' RISHBETH,j. (1952). Control of Fomes annosus Fro Forestry 25, 41-5°. RISHBETH,j. (1961). Inoculation of pine stumps against infection by Fornes annosus,

Nature, Lond. 191, 826-827. RISHBETH,J. (1963). Stump ptotection against Fornes annosus. III. Inoculation with Peniophora gigantea. Ann. appl. Biol. 52, 63-77. EXPLANATION OF PLATE

26

Hyphal interference by Peniophora gigantea, growing from left to right, against Heterobasidion

<2nnosum, growing upwards. Fig. I. The zone of contact between a colony of P. gigantea and one of H. annosum. The contacted cells of the Heterobasidion are killed (arrows) and are either transparent or granular. Fig. 2. Remains of the cell contents of the affected cells of H. annosum (arrows) are mainly located at the point of contact with the Peniophora hyphae.

ULTRASTRUCTURE OF AN ALBI~-o STRAIN OF ALTERNARIA BRASSICICOLA R. CAMPBELL

Department of Botany, The Unioersiiy, Bristol BS8

1

UG

The origin and general characteristics of an albino strain of Alternaria hrassicicola (Schw.) Wiltshire, have already been published (Campbell, Lamer & Madelin, 1968): this report compares its ultrastructure with that of the wild type (Campbell, 1968; 1969; 1970). The albino strain was grown on potato-dextrose agar at 25 °C for Trans. Br. mycol. Soc. 54 (2), (1970). Printed in Great Britain