Notes and brief articles

DEMONSTRATION OF CHLAMYDOSPORES AND EVIDENCE FORMICROSCLEROTIA IN PERICONIA MACROSPINOSA

BY GEOFFREY HALL

Department of Applied Biology, University of Cambridge , Cambridge, CB2 ]DX, U.K.

Periconia macrospinosa produced chlamydospores in agar culture and in the roots of sterilewheat seedlings, in which microsclerotia were also formed.

347

Periconia macrospinosa Lefebvre & Johnson wasfirst described by Lefebvre, Johnson & Sherwin(1949) from milo roots in Kansas, U.S.A. Since thenit has often been isolated from the rhizospheres androots of plants in arable soils (Domsch, Gams &Anderson, 1980). Hoes (1962) isolated it fromroots of winter wheat, finding that it was morefrequently isolated during the later stages of plantgrowth. During an investigation into the fungiassociated with root senescence in winter wheat,P. macrospinosa was isolated from 1 cm rootlengths which had been surface sterilized in 1%NaOCI, rinsed in distilled water and plated on to2 % water agar (Bacto-Agar, Difco Ltd, U.S.A.).Close inspection of colonies grown from singleconidia on 2 % water agar revealed the presence ofchlamydospores.

Chlamydospores have only once been reported inPericonia, in P. circinata (Mangin) Sacco by Leukel(1948). There is no mention of chlamydospores inother treatments of Periconia (which include P. cir­cinara) given by Mason & Ellis (1953), Rao &Dev Rao (1964), Ellis (1971, 1976) and Sub­ramanian (1971).

Chlamydospores were formed within 14 d andwere most easily seen through the reverse of theagar plate (Fig. 1A). They developed fromswellings in hyphae which were cut off by theformation of cross walls . Droplets were formedinside the spores and later a dark pigmentationdeveloped (Fig. 1B). They occurred singly, or moreoften in chains of two to four, and were allintercalary. The average diameter (±S.E.) of 100mature chlamydospores was 21'1 ±0'30 psi: (range14'6-29'3 ,urn). Most were formed near the surfaceof the agar.

Wheat seeds (cv. Avalon) were surface sterilizedusing the method of Speakman & Kruger (1983),plated on to 10% Tryptone Soy Agar (Oxoid Ltd,U.K.) and incubated for 3 d at 25 °C in the dark.Sterile seedlings were placed on to slopes ofStandard Complete Nutrient Solution (Hewitt ,1966) made up with 2 % agar in 20 em screw-capboiling tubes . Aluminium foil was wrapped aroundthe tube base to exclude light. Seedling roots wereinoculated with conidia of P . macrospinosa andincubated for 14 d at 25° with a cycle of 18 h light

(from tungsten bulbs) and 6 h darkness. Roots wereremoved after 14 d, lightly cleared in 5 % KOH for15 min at 90°, mounted on slides in lactophenol andobserved under x 100 and x 400 magnification.Chlamydospores (and microsclerotia) were ob­served in the root cortical cells (F ig. 1C), but couldnot be seen in roots of uninfected control plants.Similar chlamydospores were also seen in wheatroots from field samples which had been clearedand stained by the method of Phillips & Hayman(1970), in close proximity to groups of conidio­phores (Fig. 1D ).

In a study of crater disease of summer wheat inAfrican drylands, Scott, Visser & Rufenacht (1979)described dark, sclerotium-like bodies occupyingcells of dead wheat roots colonized by P. macro­spinosa which were termed microsclerotia. Theyconsisted of large, thick-walled, angular cells upto 15 Ilm diam, which under moist conditionssometimes gave rise to conidiophores and conidiaof P. macrospinosa. Similar structures were seen inthe roots of sterile wheat seedlings (Fig. 1C), butwithout conidiophores. They were also seen inclose proximity to conidiophores bearing conidia ofP. macrospinosa in wheat roots obtained from fieldsamples (Fig. 1E), but only infrequently was anyconnexion observed between the microsclerotia andthe conidiophores (F ig. 1F, G ). Many morechlamydospores and microsclerotia were seen in theroots examined that were conidiophores bearingconidia, although this was probably a result oftissue processing.

Dispersal of fungal propagules occurs in space,extending the range of a fungus , and in time,ensuring its perennation. It is more likely thatchlamydospores and microsclerotia are the struc­tures in which P. macrospinosa would be found inthe soil, dispersing the fungus in time. The conidiamay also act in a similar manner, but noinformation on this subject is available .

REFERENCES

D OMSCH, K., GAMS, W. & ANDERSON, T.-H. (1980) . ACompendium of SoilFungi,1. London: Academic Press.

ELLIS, M . B. (1971) . Dematiaceous Hyphomy cetes. Com­monwealth M ycological In stitute, Kew .

Notes and brief articles

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Fig. 1. For legend see facing page.

Notes and brief articles 349ELLIS, M. B. (1976). More Dematiaceous Hyphomycetes.

Commonwealth Mycological Institute, Kew.HEWITT, E. J. (1966). Sand and water culture methods used

in the study of plane nutrition. Technical CommunicationNo. 22, rev. znd ed, pp. 434-436. Farnham Royal,U.K.: C.A.B.

HOES, J. A. (1962). Dynamics of the mycoflora ofsubterranean parts of winter wheat in the dryland areaof Washington (abstract). Phytopathology 62, 736.

LEFEBVRE, C. L., JOHNSON, A. G. & SHERWIN, H. S.(1949). An undescribed species of Periconia. Mycologia41, 416-419.

LEUKEL, R. W. (1948). Periconia circinata and its relationto milo disease. Journal of Agricultural Research 77,201-221.

MASON, E. W. & ELLIS, M. B. (1953). British Species ofPericonia. Mycological Papers (C.M.I.) 56, 1-127.

PHILLIPS, J. M. & HAYMAN, D. S. (1970). Improvedprocedure for dearing roots and staining parasiticand vesicular-arbuscular mycorrhizal fungi for rapidassessment of infection. Transactions of the BritishMycological Society 55, 158-160.

RAo, P. R. & DEV RAo (1964). Evolutionary trends withinthe genus Periconia. Mycopathologia et MycologiaApplicate 22, 285-310.

SCOTT, P. R., VISSER, C. P. N. & RUFENACHT, E. M. C.(1979). Crater disease of summer wheat in Africandrylands. Plane Disease Reporter 63, 836-840.

SPEAKMAN, J. B. & KRUGER, W. (1983). A comparison ofmethods to surface sterilise wheat seeds. Transactionsof the British Mycological Society 80, 374-376.

SUBRAMANIAN, C. V. (1971). The genus Periconia fromIndia. Mycologia 37, 576-581.

PROTOPLASMIC FLOW IN HYPHAE

BY C. T. INGOLD

11 Buckner's Close, Benson, Oxford OX9 6LR

It is suggested that the commonly observed forward streaming from cell to cell in septatehyphae represents movement within the protoplast, not transmigration of the protoplasm asa whole.

In his Benefactors' Lecture Gregory (1984)presented a lively and thought-provoking picture ofthe fungal mycelium, and paid warm tribute to thebeautiful and fundamental work of Buller (1933).Gregory proposed the term 'transmigration' forthe 'mass migration of living protoplasm along aroute in the mycelium'. He commented withenthusiasm on Langeron's (1945) idea that 'afungus is a nucleate cytoplasmic mass which movesin a centrifugal direction, either without restraint,or inside tubes which it builds gradually as it movestowards the periphery' (his free translation fromthe French). To Langeron slime moulds andEumycetes were all fungi, with the implication thata hypha is just an extending tube in which aplasmodium creeps forward.

To me this concept is unconvincing. In thegrowing mycelium of a septate fungus, while thereis often conspicuous streaming of visible particlesmainly towards the apical growing region, thereseems to be no mass flow of the whole protoplast.

It is necessary to consider what constitutes the

living protoplast. It is surely all that is contained bythe intact plasmalemma. Thus vacuoles, which mayultimately occupy the greater part of the cell(hyphal compartment), are membrane-bound inclu­sions in the protoplasm. The forward streaming,often readily observable in septate hyphae underhigh power, is really the movement of visibleparticles within the protoplast.

In a young mycelium of a higher fungus the livingprotoplast is co-extensive with the mycelium. Thusin Pyronema confiuens (Pers.) Tul. grown from acentral inoculum on 0'2 % malt agar at 20°C, thecolony is several centimetres in diameter after acouple of days. It is then a highly branchedanastomosing system of hyphae, but all theintercommunicating segments contain living proto­plasm. Active streaming is to be seen through poresin the septa, but there is no mass flow of the wholeprotoplast away from the centre. Nevertheless,protoplasm in the peripheral compartments iswithout vacuoles, while towards the centre of thecolony the cells are highly vacuolate.

Fig. 1 (A-G). Periconia macrospinosa. (A) Chlamydospores produced in 2 % water agar. (B) Chlamydosporechain in 2 % water agar. (C) Chlamydospores and microsclerotia in the root of a sterile wheat seedling.Preparation lightly cleared. (D) Chlamydospores in a wheat root from a field sample. Preparation cleared.(E) Chlamydospore and microsclerotia associated with a conidiophore in wheat root from a field sample.Preparation cleared. (F) Microsclerotium and conidiophore in a wheat root from a field sample. Preparationcleared. (G) Microsclerotia giving rise to conidiophores in a wheat root from a field sample. Preparation lightlycleared. Scale bars represent 50 11m, unless otherwise stated.