Biological Species in Pleurotus
INTERSTERILITY GROUP
ISG VII. Pleurotus cystidiosus O.K. Miller.
1969. Mycologia 61: 889.. 1969. Mycologia 61: 889.
Nomenclatural history: Although numerous later names are perhaps synonymous, the epithet cystidiosus is priorable and therefore correct.
Typification: UNITED STATES, Indiana, Brown Co., Hoosier Nat. Forest, [?1966], coll. F.H. Berry CS-66-083-A (BFDL; perhaps now at Madison, Wisconsin).
Taxonomic history: Miller (1969) took care to investigate the name Pleurotus corticatus (Fries: Fries) Kummer, which Kaufert (1935, 1936) used for a southern North American Pleurotus which produced coremioid asexual spores. Fries (1821: 179), however, attributed a partial veil to basidiomata of P. corticatus, a feature of P. dryinus, which was later found to produce brown arthrospores but not coremioid black conidia.
Basidiomata can be recognized by the presence of white coremia surmounted by black heads of arthroconidia on the stipes and basal mycelium. Because the occurrence of the anamorphic state coupled with the teleomorph basidiomata is noteworthy, several names have been proposed for similar organisms. Their independence (morphological or genetic) is imperfectly known, but Hilber (1993, 1997) cites P. cystidiosus var. abalonus (Han et al.). Zervakis (1998) also cites abalonus as an infraspecific taxon under P. cystidiosus based on sexual compatibility experiments. At the same time, he rejects P. cystidiosus var. formosensis Montcalvo (1995) as separate from the typical P. cystidiosus, again based on sexual intercompatibility between isolates of the two.
Formation of such coremia has been reported by Segedin et al. (1995) for P. purpureo-olivaceus, which differs in basidiome size (much larger than P. cystidiosus), deep olive-black pileus (tan to brown shades for P. cystidiosus) and gray lamellae (white for P. cystidiosus). Moreover, at present, P. purpureo-olivaceus has been reported only from New Zealand and Australia.
Genetic isolation history: Moore (1985) used monokaryon isolates from widely scattered locations (i.e. South Africa, southern North America, Taiwan), obtaining intercompatibility among all. He conjectured that P. cystidiosus generally fruited in a biogeographic band bounded by about 35o north and south. Zervakis (1998) worked with additional strains (not including Kaufert’s or Moore’s) and concluded that P. smithii was an independent intersterility group.
Both authors (Moore, 1985; Zervakis, 1998) concluded that P. cystidiosus comprised only a small number of A factors and B factors, based on the repetitive occurrence of these factors from widely disbursed collections. This is in sharp contrast to other investigated species of the genus (P. pulmonarius, Petersen and Hughes, 1993; P. ostreatus, Vilgalys, pers. comm.) in which redundant mating types are very infrequent.
Culture characteristics: see Hilber (1997). In culture under ambient conditions, the anamorph dominates, to the exclusion of basidiomata.
Mating system: tetrapolar (teste Kaufert, 1936, as P. corticatus). [no data on mating system by Hilber (1982, 1997) or Miller (1969)]
Self-cross (viz. Kaufert, 1936): UNITED STATES, Louisiana, Oak Grove, no date, culture no. 2A; UNITED STATES, Mississippi, Louise Rd., no date, culture no. 2F. Also Zervakis (pers. comm.).Moore (1985) used some of Kaufert’s dikaryotic strains to produce monokaryon isolates, which were deposited at CFMR (Madison, WI), CBS and ATCC. Correspondence of Moore’s codes with ATCC accession numbers follows: B-SA(0) = 34457; B-SA(1) = 34461; B-SA(7) = 34459; B-SA(8) = 34458. Tester strains are not available from our lab.
Moore (1985) established that haploid cultures produced haploid conidia, while conidia from dikaryon cultures were dikaryotic. Monokaryotic conidia could be used as gametic units in self-crosses in the same way that neohaplonts can be so used.
Anamorphic state: Antromycopsis macrocarpa (Ellis & Everh.) Stalpers et al. (1991; but see Pollack and Miller, 1976). Study of the anamorphic state commands a separate literature (see Moore, 1977, 1984).
Additional information: Guzmán et al (1980) and Mora et al (1984) used the name P. smithii and reported its occurrence in South America and Mexico together with its anamorphic state. Zervakis (1998) found isolates under the name P. smithii to be incompatible with isolates of under P. cystidiosus (including P. abalonus) and concluded that P. smithii was a discrete genetic unit.
Infraspecific taxa have been proposed: subsp. cystidiosus (autonym), subsp. abalonus (Han et al.) Hilber (1993; = Pleurotus abalonus Han et al. 1974. Mushroom Sci. 9: 168-170.).
Miller (1969) reported that dikaryon cultures only reluctantly produced basidiomata, and that seemingly mature in vitro basidiomata did not form lamellae and did not discharge basidiospores. Only basidiomata formed on a wood block successfully discharged basidiospores.