7. M. vespa_Mycol Res-1998.pdf

Mycol. Res. 102 (10) : 1274–1276 (1998)

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Mycosphaerella vespa sp. nov. from diseased Eucalyptus leaves in Australia

A. J. C A R N E G I E1* A N D P. J. K E A N E2 " School of Forestry and Resource Conservation, The University of Melbourne, Parkville, 3052, Australia # School of Botany, La Trobe University, Bundoora, 3083, Australia

Mycosphaerella vespa sp nov. is described from diseased leaves of Eucalyptus from south-eastern Australia. It is associated with small, circular to irregular lesions that have red-brown margins and amphigenous pseudothecia. These characters, in combination with ascospore morphology and germination, distinguish M. vespa from previously described species of Mycosphaerella on eucalypt leaves. Lesions associated with this pathogen were often found to be harbouring wasps and this observation is discussed.

At present, 26 species of Mycosphaerella have been described from leaves of various Eucalyptus species in Australia and elsewhere (Corlett, 1991 ; Crous et al., 1993 ; Carnegie & Keane, 1994, 1997 ; Crous, 1996 a, b ; Crous, Carnegie & Keane 1995 a–c ; Crous & Wingfield, 1996, 1997). Many of these have been described in the last decade as a consequence of the increased interest in diseases of eucalypts in commercial plantations. More species are currently being described (P. W. Crous, personal communication). During assessments of disease caused by Mycosphaerella species in eucalypt plantations throughout south-eastern Australia (Carnegie, unpublished data ; Dungey et al., 1997), and surveys of eucalypts throughout this region, we observed a new species of Mycosphaerella. It is described here and the association of this pathogen with wasps observed in leaf spots is discussed.

Lesions amphigenous, circular to irregular, mostly less than 5 mm diam., rarely confluent, light-brown to red-brown becoming grey with age, with a red-brown margin that is often raised and occasionally callused, especially along leaf veins ; wasps are often found in cavities within lesions which causes the centre of the lesion to rise. Pseudothecia amphigenous, immersed in stomata, scattered, often more common in the centre of lesions, black, globose, 73–130 µm diam. Asci fasciculate, bitunicate, aparaphysate, subsessile, eight-spored, obclavate to cylindrical, straight or curved, 40–52¬7– 10±5 µm. Ascospores 2-multi-seriate, hyaline, 1-septate, ends obtusely rounded, slightly constricted at the median septum or not so, widest in the middle of the apical cell, slightly tapered towards the basal end, 9±5–16±5¬2±5–4 µm. Anamorph. Not seen.

Mycosphaerella vespa Carnegie & Keane, sp. no. (Figs 1–3) Etym. : after its association with wasps in leaf spots Maculae amphiginae, circulares ad irregulares, plerumque minus quam 5 mm diam., raro confluentes, dilutae brunneae ad rubrae-brunneae transeuntes griseae cum aetate, cum margine rubro-brunneo plerumque subelevato ad interdum calloso, imprimis per folii veinas ; vespa plerumque in cavitatibus in maculis efficiens centrum tumidum. Pseudothecia amphigena, immersa in stomatibus, dispersa, plerumque plura in centris maculorum, nigra, globosa, 73–130 µm diam. Asci fasciculati, bitunicati, aparaphysati, subsessiles, ocospori, obclavati ad cylindrici, recti vel curvati, 40–52¬7–10±5 µm. Ascosporae 2-multiseriatae, hyalinae, 1-septatae, cellulis basalibus et apicalibus obtusis, constrictione ad septum vel non, latissimae ad medium cellulae apicalis, attenuatae ad cellulam basalem, 9±5–16±5¬2±5–4 µm.

Holotypus : on E. globulus, Flynn, Gippsland, Victoria, Australia, 10 Mar. 1995, A. J. Carnegie (DAR 72449 ex-type culture, DAR 72449). * Current address : Forest Research and Development Division, State Forests of NSW, PO Box 100, Beecroft, 2119, Australia.

Ascospore germination on malt-extract agar (MEA). Ascospores of M. vespa germinate at 25 °C after 24 h on MEA from the apices of both cells, parallel to the long axis of the spore (Fig. 3). Occasionally, a third germ tube grows at an acute angle from the median septum end of one of these cells (Fig. 3). Ascospore cultures. Single spore cultures are relatively fast growing, reaching 45–75 mm diam. in two months. Submerged mycelium is thin and grey-green to brown, often becoming dendritic towards the outer margins. Aerial hyphae are light grey to white and fluffy, becoming sparser towards the edge of cultures. Sclerotium-like structures are scattered throughout. These are probably pseudothecial initials, but do not mature on MEA. Distribution. South-eastern Victoria, Australia. Specimens examined. M. vespa on E. globulus, Flynn, Gippsland, Victoria, Australia, 10 Mar. 1995, A. J. Carnegie (Holotype – DAR 72449 ex-type culture, DAR 72449) ; on E. globulus, Doves Block,

A. J. Carnegie and P. J. Keane

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Figs 1–3. Mycosphaerella vespa. Fig. 1. Leaf spot on E. globulus showing irregular outline and circular hole associated with wasp (arrowed) ; Fig. 2. Asci and ascospores (Bar, 10 µm) ; Fig. 3. Ascospore germination at 25° after 24 h on MEA (Bar, 10 µm). Flynn, Gippsland, Victoria, Australia, 10 Mar. 1995, A. J. Carnegie (DAR 72445) ; on E. viminalis Sm., Calignee, Gippsland, Victoria, Australia, 10 Mar. 1995, A. J. Carnegie (DAR 72444) ; on E. globulus, Mount Worth State Park, Gippsland, Victoria, Australia, 14 Apr. 1994, A. J. Carnegie (DAR 72446) ; on E. globulus, Darlimurla, Gippsland, Victoria, Australia, 8 Nov. 1994, A. J. Carnegie (DAR 72443) ; on E. globulus, Korumburra, South Gippsland, Victoria, Australia, 27 Sep. 1994, A. J. Carnegie (DAR 72447) ; on Eucalyptus sp., Angahook Forest Park, Ayres Inlet, Victoria, Australia, 30 June 1994, P. J. Keane (DAR 72442).

Mycosphaerella vespa was found infecting leaves of E. globulus and less commonly E. viminalis in progeny trials and along roadsides in south-eastern Australia. Leaf spots associated with this fungus were more common on adult and intermediate foliage of E. globulus than juvenile foliage of this host. M. vespa differs from previously described species of Mycosphaerella in the combination of various morphological characters including mode of ascospore germination and cultural characteristics. Ascospores of M. vespa are tapered and germinate from both ends, parallel to the long axis of the spore, with a third germ tube occasionally germinating at an acute angle. Ascospore cultures on MEA are very fast growing (45–75 mm diam. in two months) and light grey to grey-green in colour with sclerotium-like structures scattered throughout. In contrast, ascospores of M. cryptica (Cooke) Hansf., a species also associated with circular to irregular lesions with amphigenous pseudothecia (Crous et al., 1995 a ; Parke & Keane, 1982) like M. vespa, do not taper and germinate from one cell, with the germ tube being formed perpendicular to

the long axis of the spore. Ascospore cultures of M. cryptica on MEA are very slow growing (5–15 mm diam. in two months) and often cause a discolouration of the agar (Crous et al., 1995 a), unlike M. vespa. There are a number of species of Mycosphaerella recorded from Eucalyptus that germinate from both apices of the ascospore and form germ tubes parallel to the long axis of the spore, similar to M. vespa. These include M. nubilosa (Cooke) Hansf., M. molleriana (Thu$ m.) Lindau, M. marksii Carnegie & Keane and M. juvenis Crous & M. J. Wingf. (Crous, Wingfield & Park, 1991 ; Carnegie & Keane, 1994 ; Crous & Wingfield, 1996). M. vespa differs from these, however, in having ascospores that are constricted at the septa ; M. nubilosa, M. molleriana, M. marksii and M. juvenis do not have constricted ascospores. Ascospores of M. marksii also have an asymmetrical apical cell, which distinguishes it from M. vespa. Cultures of M. nubilosa, M. molleriana and M. juvenis are generally dark grey to olivaceous green and slow growing (less than 30 mm diam. in one month), where those of M. vespa are very fast growing and light-grey to green in colour. M. vespa can also be distinguished from these other species by its occurrence on adult foliage : M. nubilosa, M. molleriana and M. juvenis have never been recorded from adult foliage. The association of this fungus with wasps may also distinguish M. vespa from other Mycosphaerella species occurring on eucalypts. When lesions with raised centres associated with M. vespa were cut open wasps from an unidentified family were often observed in a cavity within the raised part of the lesion. Both adults and}or shed pupal cases were observed in these cavities. Many of these lesions also

Mycosphaerella vespa from diseased Eucalyptus leaves had a circular to oblong hole that joined the cavity to the outside (Fig. 1). In these lesions only shed pupal cases from wasps were found. This raises the question whether M. vespa is a primary pathogen or a secondary invader of eucalypt leaves damaged by the insect. We have never found wasps in association with other species of Mycosphaerella and no observations of wasps associated with Mycosphaerella have been reported. Further work is required to establish the pathogenicity of M. vespa and to determine the precise relationship between M. vespa and the wasp on Eucalyptus leaves. We thank Dr T. New, School of Zoology, La Trobe University, Australia, for identification of the wasp and helpful discussion, and Mr J. A. Simpson, Forest Research and Development Division, State Forest of NSW, for helpful comments on drafts of the paper. Mr T. Phillips, School of Botany, La Trobe University, assisted with photography, and Ms D. Kent, Forest Research and Development Division, State Forest of NSW, assisted with the line drawings.

REFERENCES Carnegie, A. J. & Keane, P. J. (1994). Further Mycosphaerella species associated with leaf diseases of Eucalyptus. Mycological Research 98, 413–418. (Accepted 21 January 1998)

1276 Carnegie, A. J. & Keane, P. J. (1997). A revised Mycosphaerella gregaria nom. nov. for M. aggregata on Eucalyptus. Mycological Research 101, 843–844. Crous, P. W. (1995 a). IMI Descriptions of Fungi and Bacteria : Mycosphaerella gracilis ; M. heimii. Mycopathologia 130, 49–52. Crous, P. W. (1995 b). IMI Descriptions of Fungi and Bacteria : Mycosphaerella parkii ; M. suberosa. Mycopathologia 130, 57–60. Crous, P. W., Carnegie, A. J. & Keane, P. J. (1995 a). IMI Descriptions of Fungi and Bacteria : Mycosphaerella cryptica ; M. delegatensis. Mycopathologia 130, 45–48. Crous, P. W., Carnegie, A. J. & Keane, P. J. (1995 b). IMI Descriptions of Fungi and Bacteria : M. marksii ; M. molleriana. Mycopathologia 130, 53–56. Crous, P. W., Carnegie, A. J. & Keane, P. J. (1995 c). IMI Descriptions of Fungi and Bacteria : Mycosphaerella swartii ; M. walkeri. Mycopathologia 130, 61–64. Crous, P. W., Ferreira, F. A., Alfenas, A. & Wingfield, M. J. (1993). Mycosphaerella suberosa associated with corky leaf spots on Eucalyptus in Brazil. Mycologia 85, 705–710. Crous, P. W. & Wingfield, M. J. (1996). Species of Mycosphaerella and their anamorphs associated with leaf blotch disease of Eucalyptus in South Africa. Mycologia 88, 441–458. Crous, P. W. & Wingfield, M. J. (1997) Colletogloeopsis, a new coelomycete genus to accommodate anamorphs of two species of Mycosphaerella on Eucalyptus. Canadian Journal of Botany 75, 667–674. Crous, P. W., Wingfield, M. J. & Park, R. F. (1991). Mycosphaerella nubilosa, a synonym of M. molleriana. Mycological Research 95, 628–632. Dungey, H. S., Potts, B. M., Carnegie, A. J. & Ades, P. K. (1997). Mycosphaerella leaf disease : Genetic variation in damage to Eucalyptus nitens, E. globulus and their F hybrid. Canadian Journal of Forest Research 27, " 250–259. Park, R. F. & Keane, P. J. (1982). Three Mycosphaerella species from leaf diseases of Eucalyptus. Transactions of the British Mycological Society 79, 95–100.