202 Transactions British Mycological Society

REFERENCES

BUSHNELL, W. R. (1968). In vitrodevelopment of an Australian isolate of Puccinia graminisf. sp. triciti. Phytopathology 58, 256-257.

CLELAND, W. W. (1964). Dithiothreitol, a new protective reagent for SH groups.Biochemistry 3, 480-482.

COFFEY, M. D. , BOSE, A. & SHAW, M. (1969). In vitro growth of gelatin suspensions ofuredospores of Puccinia graminis f. sp. triciti. Canadian J ournal ofBotany 47, 1291-1293.

JONES, D. R. (1972). In vitro culture of carnation rust Uromyces dianthii. Transactions ofthe British Mycological Society 58, 2g-36.

K UHL, ] . L. , MACLEAN, D.]. , SCOTT, K.]. & WILLIAMS, P. G. (1971). The axenicculture of Puccinia species from uredospores: experiments on nutrition and variation .Canadian Journal of Botany 49, 201-209.

MOORE, W. B. (1968). Solidified media suitable for the cultivation of Clostridium nOlD'itype B. Journalof General Microbiology 53, 415-423.

TUREL, F. (1969). Saprophytic development of the flax rust Melampsora lini race 3.Canadian Journal of Botany 47,821-823.

WILLIAMS, P. G., SCOTT, K .]. & KUHL, ]. L. (1966). Vegetative growth of Pucciniagraminis f. sp. triciti in vitro. Phytopathology 56, 1414-1419.

WILLIAMS, P. G., SCOTT, K.]., KUHL,]. L. & MACLEAN, D.]. (1967). Sporulation andpathogenicity of Puccinia graminis f. sp. triciti grown on artificial medium. Phyto­pathology 57, 326--327.

WONG, A. L. & WILLETTS, H .]. (1970). Observations on growth of selected Australianraces of wheat stem rust in axenic culture. Transactions of the British MycologicalSociety 55, 231- 238.

EXPLANATION OF PLATE 15Fig . I. Small amount of mycelia produced by P. graminis tritici race I 26-ANZ-6, 7 from a clumpof spores after 2 weeks' growth on the basic culture medium.Fig. 2. A small colony of P. graminis triticirace 126-ANZ-6, 7 which has grown from a single sporewhen the basic medium was supplemented with 1'0 mg DTT/IO ml of medium.Fig. 3. Vesicle-like structures of P. graminis triticirace I 26-ANZ-6, 7. These were more abundantat the lower concentrations of DTT (0'1- 0'5 mg/IO ml of medium).Fig. 4. An infection structure of P. graminis tritici race 21-ANZ-2, 3, 7 from which a sparsemycelium has developed .

ECTENDOMYCORRHIZA OF PACIFICMADRONE (ARBUTUS MENZIESII)

B. ZAK

Forest Sciences Laboratory, Pacific Northwest Forest andRange ExperimentStation, U.S. Department of Agriculture, Corvallis, Oregon, U.S.A.

Probably all plants ofthe Ericaceae are mycorrhizal. Their mycorrhizas,as Harley (1969) has pointed out, are typified by intracellular penetrationby septate hyphae. Mycorrhizas of Arbutus species may be sheathed by afungal mantle much like that of ectomycorrhizas of many forest trees.However, little is yet known of these fungus-root structures. Least knownare the fungi which are symbiotically associated with them.

Described here is an ectendomycorrhiza of Pacific madrone (Arbutus

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menriesii Pursh) formed by Cortinarius zakii J. F. Ammirati sp. provo(Dr J. F. Ammirati, University of Michigan, kindly granted permissionto use this provisional new name) from western Oregon. Gross mor­phology and anatomy of the mycorrhiza are included, as well as micro­scopic details of attached mycelium of the fungal symbiont.

The mycorrhiza (PI. 16, fig. I), now designated Arbutus menriesii +Cortinarius zakii, was discovered in a second-growth mixed Douglas-fir(Pseudotsuga menriesii (Mirb.) Franco) and grand fir (Abies grandis (DougI.)Lindl.) stand containing scattered Pacific madrone and Oregon white oak(Quercus garryana DougI.). The stand is located along the eastern marginof the Coast Ranges in western Oregon at an elevation of 200 m. Themycorrhiza probably occurs throughout much of the range of Pacificmadrone along the west coast from California to British Columbia. Itsfrequency, however, is believed to be low.

In western Oregon it can be observed during most of the rainy season,from late October to the end of May. It is most easily located whenCortinarius zakii sporophores are present; madrone roots gathered beneatha sporophore will invariably bear the mycorrhiza. Depth of occurrence inthe soil is usually 2-10 em.

Mycorrhiza is ramiform; elements straight, (120-)200(-260) pm indiameter, sheathed by well-formed fungal mantle from which wefty,sheet-like mycelium extends and merges into short, flat to round, irregularrhizomorphs (PI. 16, fig. I); finely crusty, glistening mantle and attachedfungal tissue bright golden yellow (5Y; 8'5/H~*), often changing when oldto copper (2'5 YR; 6/12) or even dull coral (5 YR; 7/6); long-waveultraviolet light fluorescence of fungal tissues weak, dull orange to darkbrown (approximately 2'5 YR; 5/10); golden yellow fungal tissueimmediately turns dull yellow (approximately 5Y; 8'5/8) to dull brown(approximately IO YR; 6/6), and copper tissue vinaceous (approximately2'5 R; 4/10) in 15% potassium hydroxide and concentrated ammoniumhydroxide, but unchanged in guaicol, phenol, formaldehyde, chlorovanil­lin, alpha-naphthol, ferrous sulphate, concentrated sulphuric acid, andMelzer solution (according to Singer, 1962). All colour designations arebased on Munsell Book of Color, Glossy Finish Collection, Munsell ColorCo., Inc., Baltimore, Md. 1966.)

Anatomy is ectendomycorrhizal (PI. 16, figs.4, 5); mantle well-developedprosenchyma, 4-12 interwoven hyphae and (2-)6-8(-12) pm, thick;Hartig net well formed; intracellular ramifying hyphae, 1-3 pm in diam­eter, restricted to first tier cortical cells (PI. 16, fig. 6); attached hyphae(PI. 16, fig. 7) thin walled, free of to heavily covered with golden yellowamorphous deposits little affected by 5 % potassium hydroxide, diameterregular (1'5-)2-3'5(-5) pm; variable-diameter rhizomorphs have straightto undulating, mostly parallel-oriented, thin-walled hyphae of regulardiameter (1'5-)2-3'5(-6) pm bearing golden yellow incrustations becom­ing pale vinaceous in 5 % potassium hydroxide.

The fungal symbiont was identified by linking stipe base mycelium andrhizomorphs ofCortinarius zakii sporophores to mycelium and rhizomorphs

Trans. Br. mycol. Soc. 62 (I), (1974). Printed in Great Britain

204 Transactions British Mycological Societysurrounding underlying mycorrhizas according to the procedure outlinedby Zak (1971). Macroscopic and microscopic characters already listedwere compared in three separate sporophore-mycorrhiza collections.

Outwardly, the well-formed mantle with attached mycelium andrhizomorphs of Arbutus meneiesii +Cortiuarius zakii suggests an ectomycor­rhiza, rather than an ectendomycorrhiza. In fact, Douglas-fir and grandfir ectomycorrhizas also formed by C. zakii and found in close proximityto the Pacific madrone mycorrhiza appear closely similar to this mycor­rhiza except for tree species-determined size. Colour and other macro­scopic and microscopic features of attached mycelia and rhizomorphs arethe same. Except for intracellular infection of the first tier of cortical cellsand inherent cell configuration, the cross-sectional anatomy stronglyresembles that of these ectomycorrhizas. Thus, as Harley (1969) suggests,the Arbutus mycorrhiza may be regarded as a connecting link in structurebetween the ectomycorrhiza and the endomycorrhiza.

At least six other mycorrhizas (PI. 16, figs. 2, 3) were observed on rootsof Pacific madrone. A common one is formed by Cenococcum graniformeSow. Ferd. & Winge; fungal symbionts of the others were not recognized,but at least three are also basidiomycetes as evidenced by the presence ofclamp connexions on hyphae.

I thank Mrs Darlene Duff for carefully prepared microtomed sections.

REFERENCES

HARLEY, J. L. (1969). The biology ofmycorrhiza, snd ed. London: Leonard Hill.SINGER, R. (1962). The agaricales in modern taxonomy, snd ed. Weinheim: J. Cramer.ZAK, B. (1971). Characterization and identification of Douglas-fir mycorrhizae.

Proceedings of the First North American Conference on Mycorrhizae, Urbana. 1969. Mis­cellaneous Publication 1189, USDA Forest Service, pp. 38-53.

EXPLANATION OF PLATE 16Fig. I. Arbutus meneiesii-e-Cortinorius zakii mycorrhiza elements (arrows). Attachments aremycelium and rhizomorphs of fungal symbiont. Scale line equals 2 mrn.Fig. 2. Associated with C. zakii mycorrhiza on Pacific madrone roots in western Oregon is blackmycorrhiza formed by Cenococcum graniforme, and white mycorrhiza formed by unidentifiedbasidiomycete. Scale line equals 2 mm,

Fig. 3. A third mycorrhiza associated with C. zakii form on Pacific madrone roots is blackrnycorrhiza formed by unidentified basidiomycete. Mycorrhiza grossly resembles that formedby C. graniforme. Scale line equals 2 mm.Fig. 4. Cross-section of A. menziesii-s- C, zakii mycorrhiza. Note fungal mantle, and intracellularhyphae in first tier cortical cells. Scale line equals 100l"ffi.

Fig. 5. Tangential section through first-tier cortical cells of A. menziesii+C. zakii mycorrhizashowing Hartig net (arrows) between cells. Scale line equals 251"m.

Fig. 6. Longitudinal section of A. menziesii-s- C, zalcii mycorrhiza showing mantle (m) and intra­cellular hyphae (ih) in first-tier cortical cells. Scale line equals 251"m.

Fig. 7. Hyphae attached to mantle of A. menziesii+C. zalcii mycorrhiza. Clamp connexions areabundant. Mounted in 5 % potassium hydroxide, and viewed by phase-contrast lighting. Scaleline equals 10 I"m.

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