Life History Studies in the Genus Hypocrea Fr.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 84, 1956-57, Page 689

Life History Studies in the Genus Hypocrea Fr. By Joan M. Dingley, M.Sc. [Received by the Editor, August 21, 1956.] Abstract Species of Hypocrea previously described from New Zealand have been studied in pure culture and the asexual stages described. In cultures of three species mature perithecia were formed. Nine species developed conidial stages which could not be separated morphologically from one another. This conidial form, which is typical of the form species Trichoderma viride Pers. ex Fr., must therefore be regarded as common to a number of species of Hypocrea. Hypocrea sulphurea (Schw.) Sacc. produces hyaline conidia typical of the form genus Cephalosporium Corda. Species of Hypocrea Fr. recorded in New Zealand by Dingley (1951; 1956) have been grown in pure culture to ascertain the asexual spore forms associated with them. Although Tulasne (1865) related H. rufa Fr. with the conidial form Trichoderma viride Pers. ex Fr., Bisby (1939) stated that “Brefeld in 1891 proved by pure culture that ascospores of H. rufa developed Trichoderma viride as the conidial stage”. He added that Brefeld also reported on the conidial stage of Hypocrea gelatinosa (Tode) Fr. Bisby held that Trichoderma was a monotypic genus since no species so far described can be separated morphologically from the type species Trichoderma viride. Since he obtained from ascospore cultures of Hypocrea gelatinosa a conidial form typical of Trichoderma viride Bisby suggested that H. gelatinosa is a growth form or a mature form of H. rufa. Bisby also described a Cephalosporium sp. from ascospore cultures of H. pulvinata Fckl. (= H. citrina (Pers.) Fr.) Methods of isolation and culturing techniques are the same as those described previously in studies of life histories in Nectria Fr. (Dingley 1957). Life Histories 1. Hypocrea atrogelatinosa Dingley (Text-fig. I, 1) Cultures floccose, with white byssoid mycelium, usually formed in zones, media not discoloured; pigmented conidia develop within five days, giving whole surface an olive green colour. Mycelium hyaline, 4–8μ diameter, septate. Conidiophores produced singly, occasionally in tufts, branched, 8–80μ long, terminating in clusters of 2–5 phialides; phialides also produced as lateral branches, usually flask-shaped, 5–8μ long. Conidia catenulated from tips of phialides, globose or oval, 1.5–4.5 × 1.5–3μ, minutely echinulate, pigmented, often aggregated into gelatinous balls. Chlamydospores sometimes present, usually globose, 12–17μ diameter, terminal or intercalary. Cultures are typical of those of Trichoderma viride. 2 Hypocrea coprosma Dingley (Text-fig I, 2) Cultures slower growing than those of H. rufa, H. schweinitzii (Fr.) Sacc. and H. atrogelatinosa, more or less tomentose, opaque, rarely discolours media; conidia formed within seven days, forming a sage green outer zone. Mycelium 3–8μ diameter, septate. Conidiophores produced usually singly 8–100μ long, septate, branching usually immediately below the septa. Phialides borne either as short lateral branches or in terminal clusters of 2–3, usually short, 2.5–3.5 × 3.5μ. Conidia mostly globose 1.5–3.5μ, pigmented and minutely echinulate, usually aggregated into small mucilaginous balls, 10μ diameter.

Chlamydospores not present. Although appearing different in cultural characters, conidia and conidiophores are typical of those of T. viride. 3. Hypocrea hunua Dingley (Text-fig. I, 3) Cultures growing similar to H. rufa, floccose, rarely discolouring media; conidia formed within five days, olivaceous green, formed irregularly over whole surface of culture. Mycelium 4–6μ diameter, often with intercalary vesicles 10μ diameter. Conidiophores often formed in tufts, 10–80μ long, usually verticillately branched immediately below the transverse septa. Phialides arranged in terminal or lateral whorls of 2–5, short, rarely elongated, 5–10 × 2.5–5.5μ. Conidia mostly globose 3–4μ, echinulate and pigmented. Chlamydospores usually absent. Perithecia formed in cultures 4–6 weeks old. Cultures are identical with those of T. viride. 4. Hypocrea lactea Fr. Cultures similar to H. rufa, floccose, media becoming discoloured, isabelline, conidia formed within seven days, dark olivaceous, developing over whole surface of culture. Mycelium 3–8μ diameter, often slightly swollen immediately below a transverse septum. Conidiophores produced in tufts more or less verticillately branched immediately below a transverse septa. Phialides arranged in terminal or lateral whorls of 2–5, usually pyriform, 5.5–10 × 3.5μ. Conidia catenulated from tips of phialides, globose, rarely oval, 2–3.5 × 2.3–3μ, pigmented and echinulate. Chlamydospores absent. Mature perithecia were formed on a small effuse stroma on a culture approximately ten days old. This species has not hitherto been recorded from New Zealand. Collections typical of European material were obtained from Glandville Forest, Totara Flats, Westland, in April, 1955, growing on branches of dead Nothofagus fusca (Hook. f.) Oerst. The conidial stage of this species is typical of T. viride. 5. Hypocrea rufa (Pers.) Fr (Text-fig. I, 6) Cultures quicker growing than H. semiorbis and H. coprosma, floccose, sometimes discolouring media, varying from greenish blue to isabelline, especially when cultures are under two weeks old. Mature conidia formed within seven days, yellowish green, sage grey to dark olivaceous in old cultures. Mycelium 4–7μ diameter. Conidiophores formed singly or in clusters 10–100μ long, branched immediately below the septa, terminating in a whorl of phialides. Phialides also formed as lateral branches of conidiophores, flask-shaped 3–7 × 3–4μ. Conidia catenulated from tips of phialides, usually globose, 2.5–4.5 × 2.5–4μ, pigmented and echinulate. Chlamydospores often present, intercalary or terminal, globose, 7–12μ diameter. Cultures are typical of those of T. viride. 6. Hypocrea schweinitzii (Fr.) Schw. Cultures similar to H. rufa, floccose, showing distinct zones in young cultures, usually discolouring media isabelline or yellow. Mature conidia formed within seven days, yellowish green to dark olivaceous. Mycelium 3–7μ diameter. Conidiophores produced singly or in tufts, often branched. Phialides arranged in terminal whorls or immediately below transverse septa, flask-shaped, 3–7 × 3.5μ. Conidia globose or oval, 2.5–4.5 × 2–3μ, echinulate and pigmented. Chlamydospores rarely present globose, 5–8μ diameter, usually intercalary. Cultures are typical of those of T. viride.

Text-fig. I.—Fig. 1.—Conidia and conidiophores of H. atrogelatinosa. Fig. 2—Conidia and comdiophores of H. coprosma. Fig. 3—Conidia and conidiophores of H. hunua. Fig. 4- Conidia and conidiophores of H. tawa. Fig. 5—Conidia and conidiophores of H. vinosa. Fig. 6—Conidia and conidiophores of H. rufa. Fig. 7—Conidia and conidiophores of H. semiorbis.

Text-fig. II.—Conidia and conidiophores, chlamydospores and arthrospores of H. sulphurea. 7. Hypocrea semiorbis Berkeley (Text-fig. I, 7) Cultures slower growing than those of H. rufa, H. hunua, H. atrogelatinosa and H. schweinitzii, translucent, becoming floccose on the outer zone accompanied by conidial formation, yellow or bright green when mature. Conidia formed in cultures nine to ten days old, rarely pigmenting media. Mycelium 3–5μ thick. Conidiophores produced singly or in tufts, simple or branched, terminating in a whorl of 2–3 phialides; latter are also formed as lateral branches of conidiophores immediately below the transverse septa. Phialides flask-shaped, sometimes with ends attenuated, 4–6 × 2–3μ. Conidia globose or oval, 2.5–5 × 2.5–3μ, echinulate and pigmented. Chlamydospores usually intercalary, globose, 7.5–9μ diameter. Although slow growing in culture, conidia and conidiophores are typical of those of T. viride. 8. Hypocrea sulphurea (Schw.) Fr. (Text-fig. II) Cultures similar in growth form to H. rufa but white, floccose during production of conidiophores. Mycelium 4–12μ diameter, septate. Conidiophores not well defined. Phialides terminal, usually formed singly and as lateral branches of conidiophores, 7–28 × 3–4.5μ. Conidia catenulated from tips of phialides, elliptical, naviculate, sometimes clavate, 7–11 × 3–4μ, smooth, hyaline. Chlamydospores sometimes present 6–10μ, usually intercalary; lemon-shaped vesicles are usually present among the vegetative mycelium, 15–20 × 10–15μ.

Arthrospores common, formed by fragmentation of vegetative mycelium, 10–17 × 3.5–4μ. Mature perithecia were formed in cultures six weeks old. The yellow stroma at first appeared in the form of floccose tufts, but as perithecia matured it became translucent and more or less effuse. This conidial form is similar to the one described by Bisby (1939) in life history studies of H. pulvinata Fckl. (= H. citrina (Pers.) Fr.). Bisby suggested that it should be classified as a species of Cephalosporium. 9. Hypocrea tawa Dingley (Text-fig. I, 4) Cultures similar to H. rufa, floccose, often discolouring media bright yellow. Conidia formed within seven days, at first bright green, becoming olivaceous. Conidiophores formed singly or in tufts 10–80μ long, sometimes singly but usually branched, branching immediately below the transverse septa. Phialides terminal, usually in whorls of 2–3, often formed as lateral branches of the conidiophores 4.5–6 × 3.5–4.5μ. Conidia catenulated from apices of phialides, globose, oval, rarely elliptical, 2.5–4.5 × 2.5–3.5μ, echinulate, pigmented. Chlamydospores globose or oval, terminal or intercalary, 8.5–10 × 5–8.5μ, thin walled, smooth. Cultures are typical of those of T. viride. 10. Hypocrea vinosa Cooke (Text-fig. I, 5) Cultures similar to H. rufa but more or less tomentose rather than floccose, sometimes discolouring media yellow or isabelline. Mature conidia at first a yellowish green, becoming olivaceous. Mycelium 3–6μ diameter. Conidiophores usually formed in tufts, verticillately branched immediately below the transverse septa. Phialides terminal, 3–5 × 2.5–3μ, in whorls or as lateral branches of conidiophore. Conidia globose or oval, 2–4 × 2.2–5μ, echinulate, pigmented. Chlamydospores common, terminal or intercalary, usually globose, rarely pyriform, 6–7μ diameter. Cultures are typical of those of T. viride. Discussion Nine species of Hypocrea produced in ascospore cultures growth forms which could not be separated morphologically from Trichoderma viride. Although cultures varied in growth rate, type of growth, colour, and amount of conidial formation, neither the vegetative mycelium, conidia nor conidiophores showed characters sufficiently distinct and constant to make specific separation possible Perithecial stages of these nine species possess differential characters either of the stroma or spores which separate them one from another Two species, H. hunua, and H. lactea, formed in culture fertile stromata identical to stromata present in field collections. The evidence of these cultures indicated that T. viride is a conidial form common to several species of Hypocrea. Hypocrea sulphurea produced a conidial form similar to that secured by Bisby (1939) from ascospore cultures of H. pulvinata which he named Cephalosporium sp. Literature Cited Bisby, G. R., 1939. Trans. Brit. Myc. Soc., 23, 149–168. Dingley, J. M, 1951. Trans. Roy. Soc. N.Z., 79, 323–337. ——, 1956. Trans. Roy. Soc. N.Z, 83, 643–662. ——, 1957. Trans. Roy. Soc. N. Z., 84, 467–477. Tulasne, L. R and C, 1865. Selecta Fungorum Carpologia, English translation by W. B. Grove, 3, 28–30. Joan M. Dingley, M. Sc., Plant Diseases Division, Department of Scientific and Industrial Research, Auckland.