Proc. Indian Acad. Sci. (Plant Sci.), Vol. 95, No. 5, December 1985, pp. 321-331. Printed in India. Characteristics of some species of Laccaria, a fungal genus of significance to forestry, temperate and tropical F IRVING*, A CROSSLEY, P A MASON, F T LAST, J WlLSON and K NATARAJAN** Institute of Terrestrial Ecology, Bush Estate, Penicuik, Midlothian EH26 0QB, Scotland *Present address: Rothamsted Experimental Station, Harpenden, Herts. AL5 2JQ, England **Centre for Advanced Studies in Botany, University of Madras, Madras 600025, India MS received 1 August 1985 Abstraer. With an inr interest in the use of selected fungi for the production of sheathing (ecto-) mycorrhizas by eontrolled inotmlations, attempts were made to identify eoiloctions of Laccaria fruitbodies from woodland and forest sites in central Seotland and at high altitudes in southern India. Although the sizes of individual fruitbodies within coUections varied appreciably, it was nonetheless possible to sort the eollections into 2 groups using mean sizes: one group with (i) stipes (stalks) about 7mm long and 1 mm diam. and (ii) pilei (caps) 10mm diam., anda ser group with appreciably larger fruitbodies. The group of larger fruitbod'.'es was found to contain collections with either 2- or 4-spored basidia; the basidia in the group of small fruitbodies were all 2-spored. Although of similar sizes, spores of the 4-spored specimens had ditferent shapes as judged by the ratios (Q values) of spore length: spore width, separately assessed for each s~0re with its apiculus in view. They were either globose (Q = 1.01) with 8-6 spines per 9/ah , each spine being on average 1-01/ara tall---a description eonforming to Laccaria laccata (Sr Fr.) Bk. and Br- or eUiptical (Q = 1-20)with 16-3spines per 9 q 2, each spine being only 0-72 q tall--a desr conforming to Laccaria proxima (Boud.) Pat. The spores of the group of Large fruitbodies with 2-spored basidia were globose, like those of Laccaria laccata, but slightly larger and with more spines per unit atea, 11.3 per 9/ah 2, a description conforming to Laccaria ohiensis (Mont.) Sing. The spores of the group of small fruitbodies with 2-spored basidia were similarly globose but, in contra.st, were appreeiably larger, 10-1 x 9-6/tm (r with 6-3 x 6.3/xm for L. laccata), with taller (1-91 q and fewer spines, 4-2 per 9/ah 2, a desr241 conforming to Laccaria tortilis (Bolt.) S. F. Gray. Laccaria laccata, Laccaria proxima and Laccaria tortilis were colleeted in Sr Laccaria proxima and Laccaria ohiensis in India. Contrary to exper Laccaria laccata was found less frequently than Laccaria proxima, the fruitbodies of both being sometimes outnumbered by those of Laccaria tortilis in young stands of Betula spp. Keywords. Laccaria; Laccaria laccata; Laccaria ohiensis;, Laccaria proxima; Laccaria tortilis;, basidia (2- or 4-spored); Q values; spore echinulation. 1. lntroduction Arising from the work of Melin (1923), Bjorkman (1942), and Marx (1980), interest in the possibility of inoculating tree seedlings, and for that matter rooted-cuttings, with isolates of selected sheathing (ecto-) mycorrhizal fungi, has, in recent years, intensified. However, events in axenic ('sterile')conditions, unlike those in unste¡ substrates, have indicated that the successful establishment of effective mycorrhizas on seedlings is controlled by the apposite choice of fungi, the choice being guided by the concept of 'mycorrhiTal succession' (Last et al 1983; Mason et al 1983; Miller 1983). In their differing papers, mainly concerned with Betula spp. but now including PŸ sitchensis 321 322 F IrvinO et al (Bong.) CarL Deacon et al (1983), Last and Mason and their colleagues indicated that 'early-stage' fungŸincluding spr of Hebeloma, Laccaria and lnocybe were likely to be appropriate whereas 'late-stage' fungŸsuch as species of Amanita, Russula and Tricholoma would be inappropriate. The fruitbodir (basidiomes) of Laccaria spp., members of the white-spored T¡ have been found worldwide in a diverse array of forests with Laccaria laccata (Scop.: Fr.) Bk. and Br. being the spr most frequently recorded. Br 1958 and 1970 L. laccata was found at 92 of 253 sites recorded by members of the British Mycological Society, L. proxima (Boud.) Pat. at 15 and L. tortilis (Bolt.) S. F. Gray at 5 (Rayner 1979). However, in a young plantation of Betula pendula Roth. and B. pubescens Ehrh. in central Scotland, an intensive study of Laccaria fruitbodies suggestr that L. laccata might be locally uncommon (Mason et al 1982). Most of the many fruitbodies were attributed to the closely related 4-spored species L. proxima or to a rarely recorded 2-sporr species L. tortilis. As Laccaria spp. appear from experiments to be leading candidates for the controlled inoculation of containerisr and seedbext nursery stocks (Molina 1982; Mason et al 1983), it was decided to probe more deeply into the identification ofrelevant Laccaria spp. to ensure that isolates, usr for inoculating young trees, were not incorrectly named as we now know has been the case in some of our work and which we suspect may have been so elsewhere. This interest was strengthened by the parallel identitication of 2-, and 4-spor~ species of Laccaria in association with Eucalyptus spp and Pinus patula (Schl. and Chato.) in southem India (Natarajan 1977). 2. Methods 2.1 Collection and preservation of samples, and assessment of their macroscopic features Fresh fruitbodies of Laccaria spp. were collected at (a) 9 UK sites, 8 of which were in central Scotland, where speci•s of Betula, Nothofaffus and Quercus were growing in association with a diverse array of other plants and (b) 4 plantations of either Pinus patula or Eucalyptus spp. near Kodaikanal (lat. 10~ 15'N, long. 77 ~31 'E) in Tamil Nadu, southern India. These were augmented by dried specimens of L. ohiensis (Mont.) Sing. from Udhaga mandalam (Ootacamund), also in southern India. Before being dried the macroscopic characters of fully mature fruitbodies were recorded using standard procedures and techniques. Thereafter, the samples were driexi bcfore being stored in either paper envelopes or glass bottles, containing silica gel crystals. 2.2 Assessment of microscopic details, particularly of basidiospores Idr basidiospores from fresh spore prints should be examined, but to enable compa¡ with all the material from India, spores, unless otherwise stated, were air- dried. They were then rehydrated in 10 % ammonia before noting size and shape using a light microscope. 'Q' values, ratios of length to width, were calculated separately for each spore, always ensuring that the apiculus, of the spore being measured, was in view. Because the degree of resolution obtained with a light microscope was insufficient to obtain accurate measures of the sizes and distributions of spines, they were examined under a scanning electron microscope (SEU). For this, sections of gill were attached to aluminium stubs. They were then dried in a desiccator fora further 24 hr before being Characteristics of some species of Laccaria 323 coated with gold and examined. Photographs at magnifications ranging from • 1003 to x 10000 were taken and used for assessing spore charactefistics. 3. Observations (table 1) 3.1 Separation by macroscopic features of fruitbodies 3.1.1 Group of relatively laroe fruitbodies: (i) Subset A Stipe (stem) 16-110 mm long and 1-5--10-0 mm wide. CharacteristicaUy fibrillose with distinct fibres running the length of the stipe which widens at the base and is covered by a white down of hyphae. Pileus (cap) 6-47 mm diam. Convex when young but becoming flattened and often centrally depressed when old. Finely scaly when young but with a somewhat concentric pattern of dark scales on older specimens which are especially evident towards the centre of the pileus. Pileus is orange-brown when fresh, fading eventually to a light orange to yellow-brown colour. Lamellae (giUs) notas darkly coloured as pileus. They are thick and wavy. (¡ Subset B Stipe 12-50 mm long and 2"0~ mm wide. Often twisted and although slightly fibrous and tough it lacks the distinct longitudinal fibres, characteristic of Subset A. Base of stipe covered with woolly weft of hyphae. Pileus 5-33 mm. Convex when young, later becoming [iattened with a central depression. Piteus has a noticeable wavy striate margin. Ir appears to be smoother (possibly finely scurfy) than in Subset A. It does not have dark scales. Its colour ranged from a pinkish-brown when fresh to a light orangy yellow when older and dry. Lamellae are pinkish, thick and wavy: often dusted white with spores when mature. (iii) Subset C Stipe up to 45 mm long and 5 mm wide. Cylindrical solid, smooth to fibrillose, fibrils same colour as pileus. Pileus 20-30mm diam. Convex when young, becoming flattened and centrally depressed: margin incurved and lobed. Lamellae thick, Titian red compared with cinnamon brown of pileus. 3.1.2 Group of relatively small fruitbodies: (i) Subset D Stipe 2-18 mm long and 0.5-2.0 mm wide. Usually tapering to base; sometimes slightly fibrous. Pileus 2-28 mm diam. Convex when young, becoming flattened and centrally depressed: margin wavy and striated. Slight scurf on surface; flesh pinkish brown. Lamellae thick, well spaced, usually wavy and same colour as pileus. 3.2 Separation by microscopic features (Figures 1 and 2) 3.2.1 Group of relatively lar9e fruitbodies: (i) Subset A Basidiospores white in mass. Using d¡ spores anda light microscope they measured 6-8-11-1 • 6-t-9-5 #m (excluding spines). Ellipsoid and finely echinulate (spiny). Table 1. Salient characteristics of fruitbodies and spores of 4 subsets of Laccaria collected in association with trees in Scotland and/or India Subset A Subset B Subset C Subset D (L.