Effects of Cultural Conditions on Vesicle and Conidium Morphology in Species of Cylindrocladium and Cylindrocladiella

Impact of Calonectria Diseases on Ornamental Horticulture: Diagnosis and Control Strategies

Diseases caused by fungi in the genus Calonectria pose a significant threat to the ornamental horticulture industries in Europe and the United States. Calonectria spp. are particularly challenging pathogens to manage in ornamental production systems and the urban landscape for multiple reasons. A high level of species diversity and poorly resolved taxonomy in the genus makes proper pathogen identification and disease diagnosis a challenge, though recent molecular phylogenetic studies have made significant advances in species delimitation. From a disease management perspective, Calonectria spp. produce long-lived survival structures (microsclerotia) that contaminate nursery production systems and can survive multiple years in the absence of a susceptible plant host. Latent infection of plant material is poorly understood but likely contributes to long-distance dissemination of these fungal pathogens, including the clonal Calonectria spp. responsible for the global emergence of boxwood blight. Breeding for disease resistance represents a sustainable strategy for managing Calonectria diseases but is challenging due to the perennial nature of many ornamental plants and high levels of susceptibility in commercial cultivars. Ultimately, long-term sustainable management of Calonectria diseases will require an improved understanding of pathogen biology as well as integration of multiple disease management strategies.

Phytotoxic chaetoglobosins are produced by the plant pathogen Calonectria morganii (anamorph Cylindrocladium scoparium)

By the application of a bioassay based on cresson seedlings, two phytotoxic compounds were isolated by thin-layer chromatography from the culture fluid of a Calonectria morganii isolate. The structure of both compounds was elucidated by ESI/MS and NMR spectroscopy. According to the Chemical Abstracts database, they were identified as chaetoglobosin A and 19-O-acetylchaetoglobosin A, mycotoxins originally described for Chaetomium globosum.

New species of Mycosphaerella occurring on Eucalyptus leaves in Indonesia and Africa

Although Africa and Indonesia have not been particularly well surveyed for Mycosphaerella leaf spot fungi, several species are known to occur on Eucalyptus leaves in these areas. Three new species of Mycosphaerella with anamorph states are described from herbarium specimens and cultures in the present study. Mycosphaerella suttoniae and Mycosphaerella heimioides are described from Eucalyptus leaves from Indonesia. The former species is of particular interest, because its anamorph Phaeophleospora epicoccoides is the first species of Phaeophleospora linked to Mycosphaerella. Mycosphaerella irregulariramosa is described from Eucalyptus saligna growing in the Northern Province of South Africa. Both M. irregulariramosa and M. heimioides have Pseudocercospora anamorphs, and these are described as Pseudocercospora irregulariramosa and Pseudocercospora heimioides. Notes are also provided on the host range and geographic distribution of previously described species of Mycosphaerella on Eucalyptus leaves in other parts of Africa and in Indonesia. Key words: Eucalyptus, Kirramyces, Mycosphaerella, Phaeophleospora, Pseudocercospora, systematics.

Colletogloeopsis, a new coelomycete genus to accommodate anamorphs of two species of Mycosphaerella on Eucalyptus

Species in Colletogloeopsis are characterized by having acervular conidiomata, and brown, verruculose, thick-walled, aseptate conidia that are formed on brown, verruculose conidiogenous cells that proliferate sympodially or percurrently. Colletogloeum nubilosum, the anamorph of Mycosphaerella cryptica, is transferred to Colletogloeopsis. Colletogloeopsis molleriana is described for the anamorph of Mycosphaerella molleriana, formed from single ascospore isolations obtained from collections of Eucalyptus globulus leaves from Portugal and California, United States. Mycosphaerella molleriana is redescribed and distinguished from Mycosphaerella nubilosa, which was earlier regarded to be synonymous with the former. Key words: Colletogloeum, Mycosphaerella leaf blotch, systematics.

Identification of root rot fungi in nursery seedlings by nested multiplex PCR

The internal transcribed spacer (ITS) of the ribosomal DNA (rDNA) subunit repeat was sequenced in 12 isolates of Cylindrocladium floridanum and 11 isolates of Cylindrocarpon destructans. Sequences were aligned and compared with ITS sequences of other fungi in GenBank. Some intraspecific variability was present within our collections of C. destructans but not in C. floridanum. Three ITS variants were identified within C. destructans, but there was no apparent association between ITS variants and host or geographic origin. Two internal primers were synthesized for the specific amplification of portions of the ITS for C. floridanum, and two primers were designed to amplify all three variants of C. destructans. The species-specific primers amplified PCR products of the expected length when tested with cultures of C, destructans and C. floridanum from white spruce, black spruce, Norway spruce, red spruce, jack pine, red pine, and black walnut from eight nurseries and three plantations in Quebec. No amplification resulted from PCR reactions on fungal DNA from 26 common contaminants of conifer roots. For amplifications directly from infected tissues, a nested primer PCR using two rounds of amplification was combined with multiplex PCR approach resulting in the amplification of two different species-specific PCR fragments in the same reaction. First, the entire ITS was amplified with one universal primer and a second primer specific to fungi; a second round of amplification was carried out with species-specific primers that amplified a 400-bp PCR product from C. destructans and a 328-bp product from C. floridanum. The species-specific fragments were amplified directly from infected roots from which one or the two fungi had been isolated.

Foliicolous dematiaceous hyphomycetes from Syzygium cordatum

During a study of foliicolous fungi on Syzygium cordatum in South Africa, several previously undescribed or unreported fungi were collected. Two new species of Anungitea, Anungitea caespitosa and Anungitea syzygii, are described from leaf litter. An additional four new taxa are also described, Chloridium constrictospora, Parasympodiella elongata, and Vermiculariopsiella spiralis from litter, and Podosporium etheldoidgeae from living leaves. Several saprobic fungi are reported for the first time in South Africa. The morphological variation occurring in Conoplea mangenotii is discussed. Key words: foliicolous fungi, Myrtaceae, systematics, Syzygium cordatum.