Lophodermium canberrianum, a hitherto invalidly published name

Notes and brief articles

335

giving the ascospores the impression of being reticulately ornamented by light microscopy; overall dimensions (18'5-)20-28(-33) x (6-)8-11

non-ostiolate in culture, basal part of the ascomata black, carbonaceous, usually subglobose but sometimes broadly obpyriform, 80-220 pm diam; peridium pseudoparenchymatous, texrura angu- (-13) pm. laris, 15-30 pm thick, composed of 4-6(-7) layers Specimens examined. India, Bihar, on leaves of of dark brown radially compressed thick-walled cells, cells mainly 10-20 pm long, 5-7 pm thick, Pandanus sp., 23 Apr. 1977, M. A. Rizwi 32, IMI 213076; India, sine loc., on leaves of Pandanus and 10-15 pm diam in surface view, smooth- [asciculatus, comm. 4 Nov. 1976, R. S. Kanaujia RSK walled, the inner layer(s) of cells becoming 274/S, IMI 21oo39C. thinner-walled and hyaline; ostiole poorly differentiated, elongated, delicate, difficult to detect or The junior author is grateful to the British absent in culture, 80-100 pm tall and 30-50 pm Council (London) and the University Grants wide, walls composed of 1-2 layers of very Commission (New Delhi) for financial assistance irregularly shaped pale brown to brown pseudo- to visit the United Kingdom. The senior author is parenchymatous cells mainly 7-10 pm diam, indebted to Mr D . W. Fry for photographic terminating at the surface of the host and not assistance. protruding from it. Paraphyses absent . Asci arising REFERENCES in a fascicle from the base of the ascomata, subcylindrical to elongate-clavate, short-stalked, thick- VON ARX, J. A. (1975). On Thielavia and some similar walled at first but becoming very thin-walled at generaof ascomycetes. Studies in Mycology, Baam 8, 1-28. maturity, not developing synchronously, unitunicate, with a distinct refractive apical annular HAWKSWORTH, D. L. & UOAGAWA, S. (1977). Contributions to a monograph of Microthecium. Transring, 110-140 x 12-18 pm, 8-spored. Ascospores actions of the Mycological Society of Japan 18, arranged almost uniseriately to distichously in the 143-154· asci, narrowly ellipsoid to broadly fusiform, not HUGUENIN, B. (1966). Micromycetes du Pacifique Sud abruptly truncate at the apices, probably with (Quatrieme contribution). (1) Deux ascomycetes de a germ-pore at each end, usually 1- to z-guttulate, Nouvelle-Caledonie. Bulletin trimestriel de la Societe not septate, deep golden brown when mature, mycologique de France 81, 699-703. walls verruculose; verrucae densely compacted, MALLOCH, D. & CAIN, R. F. (1973). The genus convexly swollen and mainly 0'5-1 '5 pm wide, Thielaoia. Mycologia 65, 1055-1°77.

LOPHODERMIUM CANBERRIANUM, A HITHERTO INVALIDLY PUBLISHED NAME D. W. MINTER* AND C. S. MILLAR

Forestry Department, Aberdeen University AB9 zUU

In 1966 Stahl published the species Lophodermium canberrianum (Ascomycetes, Phacidiales)

without a Latin description or a designated type. He considered that it differed morphologically from L. pinastri (Schrad. ex Hook.) Chev. in lacking associated stromatic lines, in having totally subepidermal ascocarps with a dull black, less erumpent external appearance, which coalesce more frequently, in ascospores with different (though overlapping) lengths and in cultural characteristics. According to Stahl, L . canberrianum also differed ecologically, the species being restricted to pines of the ' ponderosa ' group, can tolerate dry conditions, lind can cause severe * Present address: Commonwealth Mycological Institute, Kew, Surrey. Trans. Br. mycol, Soc. 71 (2), (1978).

defoliation, whereas he notes that L. pinastri has a wide host range and has been of little economic concern in Australian Capital Territory. The morphological characters cited by Stahl, in particular those of depth of embedding of ascocarps in the host and presence or absence of stromatic lines were found recently (Minter, Staley & Millar, 1978) to be significant in distinguishing four Lophodermium species on Pinus sylvestris L. Examination of specimens of L. canberrianum at C.M.I. indicates that a Leptostroma stage is probably absent, another significant difference from other Lophodermium species on pine . Lophodermium canberrianum is therefore concluded to be a biologically good species and is validly published below.

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Notes and briefarticles

1

Fig. 1. Lophodermium canberrianum, ascocarps. x 25. Fig. 2. Lophodermium canberrianum, transverse section. x 250.

Lophodermium canberrianum Stahl ex Minter & Millar Ascocarpis in acubus amphigenis, 600-1400 jtm long., cellulis acuum epidermalibus omnino tectis, udo statu

Trans. Br. mycol. Soc. 71 (2), (1978).

nigris vel gnseis, lineola numquam circumscripta nigra, statu sicco similaribus sed fulvas aliquando iuxta rimam ostendentibus regiones quae epidermalium ob discolorationem cellulorum sane exoriuntur, Labiis hyalinis et parum saepe insignibus. Ascis cylindricis,

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Notes and brief articles octosporis, 110-150 pm long., 11-15 pm lat. Para physibus filiiformibus, apiee leniter c1avatis et ramosis rare, ascis aequilongis. Ascosporis filiformibus, 70120 pm long., mueo involutis gelatinoso et saepe versus asci apicern eonvolutas ostendentibus spirales. Desunt et pycnidia et lineare stromaticae.

Ascocarps amphigenous on needles (less than 40 % on adaxial surfaces). Wet ascocarps black or grey on either side of the split (Fig. 1), the black area having no definite margin, but merging with the browned needle a short distance from the split which often continues beyond the black surround into the browned needle area surrounding the ascocarp . Dry ascocarps often showing a tawny area immediately next to the split, th is discoloration resulting probably from the host epidermal cells, and needle stomata often darkened in the region of the ascocarp. Lips hyaline, often obscure. Ascocarps 600-1400 pm long (mean 880 pm), totally covered by the host epidermis (Fig. 2). In mid-point transverse section the development of the black stromatic clypeus is often poorly developed compared to that of L. pinastri. Asci cylindrical, 8-spored, 110-150 pm long, 11-15 pm wide. Paraphyses filiform, slightly swollen at the apex, rarely branched, the same length as asci. Ascospores filiform, 70-120 pm long, about 2 pm wide, enveloped in a gelatinous sheath and sometimes coiled spirally within the ascus . Pycnidia and stromatic lines lacking.

337

Cultures on 2 % malt agar slow-growing, growth invariably terminating before the edge of the Petri dish (90 mm diam) is reached. Cultures at first white, but rapidly gaining a characteristic orange or yellow colour and sometimes discolouring the surrounding agar, but never developing dark stromatic lines around the colony. Specimens examined. On dead needles of Pinus engelmannii Carr. Blundel's Farm Arboretum, Australian Capital Territory, 18 Dec. 1976, W. Stahl, IMI 223611, holorype ; on dead needles of Pinus ponderosa Dougl., Piccadilly Circus Arboretum, A.C.T., 18 Dec. 1976, W. Stahl, IMI 225310; on needles of Pinus ponderosa, Hall's Block, A.C.T., Mar. 1975, W. StaW, IM1213OO3. Examples of cultures may be seen with the type collections. Part of the work was supported by a Natural Environment Research Council Studentship and forms part of a Ph.D. thesis by one of us (D. W. M.) sustained recently at Aberdeen University. REFERENCES

D. W., STALEY,]. M . &MILLAR,C. S . (1978). Four species of Lophodermium on Pinus syluestris, Transactions of the B ritish Mycological Society 71 (2),

MINTER,

295-3 0 1 .

W. (1966). Needle-cast fungi on conifers in the Austra lian Capital Territory. Australian Forestry

STAHL,

30 (1) 20-32.

GERMINATION OF BREMIA LACTUCAE OOSPORES W. M. MORGAN

Glasshouse Crops Research Institute, Littlehampton, West Sussex, BN16 3PU Bremia lactucae Regel, the cause of lettuce downy

mildew, produces oospores erratically in infected leaf tissue but occasionally they occur in large numbers (Ingram, Tommerup & Dixon, 1975; Morgan, 1976). Their germination has not been reported hitherto but was implicit in investigations in which downy mildew infection of young lettuce plants occurred in the presence of leaf tissue which contained oospores (Humphreys-Jones, 1971; Morgan, 1976). After many unsuccessful attempts to germinate oospores (Morgan, 1976), r report here an account of their germination and an experiment which showed that germination was stimulated by, but was not dependent upon, the presence of germinating lettuce seed. A downy mildew isolate (virulence genes 1, 2 Trans . Br. mycol. Soc. 71 (2), (1978). 12

and 6) was maintained on lettuce seedlings of cv. Amanda Plus grown in enclosed polyethylene containers on sterile sand wetted with Hewitt's solution. They were illuminated with 5-10 W m- 2 during a photoperiod of 16 h and kept at day and night temperatures of 20 ± 0'5 and 16 ± 0'5 °C respectively. . Rotted, infected cotyledons were collected over a period of 6 months and kept at laboratory temperature in distilled water. When the cotyledons had become transparent, they were examined to confirm the presence of oospores and were then returned to water in a 9 em Petri dish . Six months after the last harvest of cotyledons, the now macerated leaf tissue was supported on 4 % distilled water agar. Using tungsten-wire spore handlers and a dissection microscope, oospores

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