BASIDIOCARPS annual, occasionally perennial, resupinate, effused-reflexed, or pileate; when pileate broadly attached, variable in shape, applanate, ungulate, or convex, often irregular, usually solitary; compressible to exude water droplets when fresh, corky hard when dry,; pilei 3.5-19 cm across, 2.5-17 cm radius, 1.5-8 cm thick at base; when effused-reflexed and extending along substrate branch, up to 62 cm long with numerous reflexed portions; when resupinate up to 50 x 36 cm. PILEUS SURFACE glabrous, concentrically sulcate in narrow to broad bands, brown to red-brown or dark brown, sometimes concentrically zonate with narrow bands of different shades of brown; at margin on actively growing pilei cream-coloured in a narrow to broad band; margin rounded or sharp. PORE SURFACE cream to light yellow-brown; pores angular to subdaedaleoid and sometimes radially elongated, 1-2(-3) per mm; tube mouths even; tubes up to 3.8 cm deep, concolourous with pore surface; in perennial fruitbodies, tubes weakly stratose and successive tube layers often receding; sterile margin 1-3 mm across. CONTEXT cream, corky, azonate, mostly less than 1 cm thick, up to 2 cm thick at base, of intertwined hyphae; cuticle dark brown, shiny when cut, to 170 µm thick, composed of brown hyphae. HYPHAL SYSTEM dimitic; generative hyphae thin-walled, simple septate, hyaline, nondextrinoid, 2.5-5.5 µm wide; skeletal hyphae dominating, straight to flexuous, sparingly branched, hyaline except in cuticle, dextrinoid, 2.5-6.5(-8) µm wide, with thickened walls to 2.8 µm thick. BASIDIA 4-sterigmate, cylindrical to clavate or sometimes slightly constricted about the middle; c. 15-18 x 6-7 µm. CYSTIDIOLES thin-walled, elongate, cylindrical, 3-6.5 µm diam., with one (rarely two) small apical bulbs; contents often granular; sometimes projecting beyond the hymenium. BASIDIOSPORES ovate, often uniguttulate; wall echinulate, hyaline in tubes, sometimes pale yellow-brown on pileus surface, up to 0.5 µm thick, IKI -; (4.7-) 5.7 (-8.3) x (3.7-) 4.6 (-6.0) µm; spore print white.
TYPE OF ROT: white.
CULTURAL CHARACTERISTICS: COLONY on malt agar, usually white, sometimes pale yellow, translucent. Marginal hyphae appressed, widely spaced. Aerial mycelium appearing farinaceous to subfelty, consisting of erect, simple or branched conidiophores. Colony reverse white or pale yellow. Optimum temperature for growth: 23-25 C. Tests for extracellular polyphenol oxidases, using gum guaiacum solution, tannic acid agar, and gallic acid agar (Nobles, 1965), positive. HYPHAE hyaline, thin-walled, up to 9 µm diam., simple septate or clamped, clamps present on wide, straight hyphae especially near margin; sulpho-positive hyphal elements present, thin-walled with short papillate side branches, cytoplasm granular or composed of tiny oil droplets; occasionally thick-walled, brown, interlocking hyphae forming crust in older parts of colony. CONIDIOPHORES arising as erect branches from prostrate hyphae, often constricted at junction with hyphae, sometimes covered with granular material at base, simple or branched, variable in length, up to 400 µm long, 5.5-13.5 µm diam., with an apical, inflated conidiogenous vesicle, 7-19.5 µm diam., from which develops conidia on conical denticles. CONIDIA subglobose, obovoid, or pyriform, unicellular, hyaline, smooth-walled, (5-) 7.6 (-16) x (3-) 5.3 (-13.5) µm; wall up to 0.5 µm thick.
SPECIES CODE (Nobles, 1965): 2,5,(6),7,(10),(11),(15),33,36,(37),38,42,50,(53),55,57.
SEXUALITY: homothallic.

DISTRIBUTION: Australia (eastern Queensland, northeastern New South Wales), New Zealand (northern North Island), Papua New Guinea, Fiji.

HOSTS: recorded on Araucariaceae (Agathis australis (D. Don) Lindley, A. vitiensis (Seem.) Benth. & Hook. f. ex Drake, Araucaria bidwillii Hook., A. cunninghamii Aiton ex Don) and Pinaceae (Pinus kesiya Royle ex Gordon, P. patula Schlecht. & Cham., P. taeda L.); on stumps or dead standing and fallen wood, rarely on living wood.

Fructificatio annua, interdum perennis, resupinata, effuso-reflexa vel pileata. Pileus late affixus, variabilis, applanatus, ungulatus vel convexus, 3.5-19 cm latus, 2.5-17 cm radius, 1.5-8 cm basi crassus, superficie glabra, concentricaliter sulcata, brunnea, interdum ad marginem cremea. Pori facies cremea; pori 1-2(-3) per mm, angulati ad subdaedalei. Contextus cremeus, ad 2 cm crassus; cutis fusca, ad 170 um crassa. Systema hypharum dimiticum; hyphae generatoriae effibulatae, hyalinae; hyphae skeletales dextrinoideae. Sporae hyalinae, ovatae, nondextrinoideae, (4.7-) 5.7 (-8.3) x (3.7-) 4.6 (-6.0) µm, muris echinulatis.

Etymology: araucariae, from host genus Araucaria (Araucariaceae).
Notes. Heterobasidion annosum sens. lat. is considered to be heterogeneous. Differences in a combination of characters separate H. araucariae from H. annosum sens. str. Some of these differences have been previously noted by other authors but in isolation they were considered insufficient to delimit a separate species.
The fruitbody of H. araucariae is most readily distinguished macroscopically from H. annosum by pore size with significantly larger pores in H. araucariae; mean number of pores per mm for 45 dried fruitbodies from Australasia ranged from 1.7-2.7, while for 80 dried fruitbodies of H. annosum from the northern hemisphere pore size was 2.8-5.9 pores/mm (Hood, 1985). In addition to larger pores, Cunningham (1965) noted the apparent absence of strata in tubes of most Australasian specimens, but reported receding tube layers in old perennial specimens. Most collections of H. araucariae examined in the present study appeared to be annual, with tubes up to 25 mm in length. In perennial fruitbodies, tube length varied from 5 to 15 mm between strata, with successive tube layers often receding. In collections of H. annosum examined, tube length between strata was shorter, 2-6 mm. Ryvarden (1976) reported up to 4 mm between strata for H. annosum. Fruitbodies of H. araucariae were often larger than those typical of H. annosum, but both species display a wide range of fruitbody size and shape.
Microscopically, H. araucariae can be distinguished from H. annosum by larger basidiospores. Mean dimensions for basidiospores of H. araucariae (344 spores measured from 20 collections) were 5.74 x 4.62 um, and for basidiospores of H. annosum (80 spores measured from 5 collections), 4.65 x 3.85 µm. The difference is statistically significant (p 0.001) for both mean length (SED = 0.06) and mean width (SED = 0.05) The range of spore size for the two species overlaps somewhat: H. araucariae 4.7-8.3 x 3.7-6.0 µm, H. annosum 4.0-6.0 x 3.2-4.5 µm. Spores of both species are of similar shape, have an echinulate wall and are binucleate (Chase et al., 1985).
In culture, H. araucariae can be distinguished from H. annosum by larger conidia (Fig. 3,4). Fifty conidia were measured from each of 3 strains of H. araucariae (Australia, New Zealand) and from 3 strains of H. annosum (France, Afghanistan, U.S.A.). Conidia were sampled from 6-week-old colonies using double-sided cellotape and mounted in 3% KOH. Mean dimensions for conidia of H. araucariae were 7.6 x 5.3 µm (range: 5-16 x 3-13.5 µm; width/length ratio: 0.69) and for H. annosum 5.3 x 4.2 µm (range: 3.5-8.5 x 2.5-6.5 µm; width/length ratio: 0.79). Differences between the two species are highly significant (p 0.001) for mean length (SED = 0.16), width (SED = 0.13), and width/length ratio (SED = 0.01). The dimensions obtained for conidia of H. annosum are close to those reported by Stalpers (1978), 4-8(-10) x 2.5-5(-6) um, but are larger than measurements given by Courtois (1972), 3.8-5.2 x 2.9-3.9 µm, and smaller than those of Korhonen (1978), mean 5.9 x 4.2 µm for P-intersterility group and 6.8 x 5.1 µm for S-group; Stenlid & Haggblom (1985) reported mean size of S-group conidia as 5.3 x 3.6 µm. The relative intersterility group of the 3 strains of H. annosum used in the present study is not known. For some fungal species there is a close relationship between spore size and nuclear volume (Tolmshoff, 1983). Considering that H. annosum and H. araucariae are closely related species, the larger conidia of H. araucariae might indicate a polyploid origin.
In other respects, cultures of H. araucariae are morphologically similar to those of H. annosum. Colonies of both species are typically white, farinaceous, with a Spiniger anamorph. Temperature optima and growth rates are similar. Hyphae are alike; sulphopositive hyphae bearing short papillate side branches, as described by Gluchoff-Fiasson et al. (1983) from cultures of H. annosum and H. insulare, also occur in H. araucariae (Fig. 2a).
Strains of H. araucariae and H. annosum can also be differentiated at the biochemical level. In a comparative electrophoretic study (unpublished data) the two species showed different alleles at two of four loci assessed, and marked differences in allele frequency at a third locus.
The name Spiniger is applied to oedocephaloid anamorphs of several species of basidiomycetes, although anamorph binomials have been published for only two of these species (Stalpers, 1974). It is considered inappropriate to publish a binomial for the anamorph of H. araucariae. In a key to the genus Spiniger (Stalpers, 1974), H. araucariae would key out beside H. insulare and S. meineckellus (A.J. Olson) Stalpers, the anamorph of H. annosum.
H. araucariae is homothallic. A survey of 43 single spore strains derived from 6 New Zealand collections showed the presence of clamped hyphal septa in all strains, although clamps were often rare and easily overlooked. Korhonen (1978) and Chase et al. (1985) reported homothallism for 3 Australian collections, and J.A. Simpson (pers. comm.) noted that single spores isolated from material collected in Papua New Guinea germinated to give clamped mycelium. In contrast, H. annosum is heterothallic with unifactorial incompatibility (Korhonen, 1978; Chase & Ullrich, 1983).
Two intersterility groups within northern hemisphere isolates of H. annosum were identified by Korhonen (1978) but 11 strains of 'H. annosum' from Australasia did not mate with either group. Subsequently, Chase et al. (1985) reported heterokaryon formation between auxotrophic mutants of Australian 'H. annosum' and some heterothallic auxotrophs of North American H. annosum. The possibility that gene flow may occur between strains of H. araucariae and H. annosum is being investigated by J. Stenlid (pers. comm.). In the light of other differences between the two taxa however, the demonstration of compatibility in vitro is not considered to negate arguments for the separation of H. araucariae from H. annosum.
The known hosts for H. araucariae are 2 species of Agathis, 2 species of Araucaria, and 3 species of Pinus. Most collections of basidiocarps are from stumps or dead wood. In New Zealand the fungus most commonly fruits on the trunk and branches of large fallen trees of Agathis australis (kauri), and on large, fallen branches shed from apparently healthy trees. It is reported to cause a sap rot of minor importance on living kauri (Gilmour, 1966). All known collections of basidiocarps on Pinaceae are from dead trunks, stumps, or logs. In northern New Zealand, on land cleared of kauri and replanted with several exotic species of Pinus known to be susceptible to H. annosum, H. araucariae has been recorded only on dead logs of P. taeda. In northern Queensland, basidiocarps of the fungus occurred on dead standing trees of Pinus patula in a stand showing high mortality, but it was not identified as the cause of death (Shain & Bolland, 1974). Although recorded on dead Araucaria cunninghamii in Papua New Guinea (Simpson, 1978), H. araucariae was not found on P. caribaea Morelet and P. patula in adjacent plantations.
Extensive plantations of Pinus radiata D. Don and Pseudotsuga menziesii (Mirb.) Franco occur throughout New Zealand. In the northern hemisphere, both species are susceptible to H. annosum (Gibson, 1979; Browne, 1968), but no Heterobasidion species has been recorded on either Pinus radiata or Pseudotsuga menziesii in New Zealand. Sutton (1965) offered the hypothesis that competition from Phlebiopsis gigantea (Fr.) Jul. could explain the non-pathogenic character of 'H. annosum' in New Zealand. However, pathogenicity tests using one-year-old Pinus taeda seedlings in a glasshouse showed that New Zealand and Australian strains (labelled H. annosum) were less virulent than strains from the northern hemisphere (Kuhlman, 1970). H. araucariae is considered to be a saprophyte or weak pathogen with a restricted host range, unlike H. annosum which is pathogenic on many coniferous hosts and other trees (Browne, 1968). Recognition of the taxonomic distinction and difference in pathogenicity between H. annosum and H. araucariae has important implications for quarantine. The introduction of H. annosum to Australasia could threaten health of exotic and endemic conifers and other susceptible species.
H. araucariae might be expected to occur on other Araucariaceae and in other parts of the geographic range of the family, which extends from Indochina through Indonesia and Philippines to Australia, New Zealand, and the Pacific Islands, and in South America from Brazil to Chile (Willis, 1973). Material of H. annosum reported from Malaysia and Vietnam (Anon., 1980) has not been examined; Parmasto (1986: 64) lists H. annosum from Vietnam but states 'possibly erroneous identification'. H. annosum has been reported on members of the Dipterocarpaceae in the Philippines (Eusebio, 1977). In Indochina, the northern limit of Araucariaceae, H. annosum and H. araucariae could possibly occur together. Neither species has been definitively recorded from South America (J.E. Wright, pers. comm.; Anon., 1980). On Norfolk Island H. araucariae was not found on the endemic Araucaria heterophylla (Salisb.) Franco (personal observation).
The third species accepted in the genus Heterobasidion, H. insulare, can be readily distinguished from H. araucariae. Pilei of H. insulare are typically imbricate, small (2.5-9 cm across, 1.5-7 cm radius, 0.2-1.0 cm thick) and coloured red, dark red or reddish brown on the pileus surface, often with a cream margin. The pore surface has smaller pores, 2-3(-4) per mm, with dissepiments often thin and pores sometimes tending irpicoid towards the base of the basidiocarp. Basidiospores measure (4.5-) 5-6 (-7) x (3.5-) 4-5 µm. H. insulare is a saprophyte, confined to Asia (India, Nepal, Burma, Japan, Philippines).

Holotypus: New Zealand, Northland, Waipoua Forest Sanctuary, Yakas Kauri Track, on fallen branch of Agathis australis, leg. P.K. Buchanan no. 85/299, 25 Sep 1985 (PDD 48002).