3.7.53
THE GENUS LEPTOGRAPHIUM -- A RE-EVALUATION

K JACOBS1, MJ WINGFIELD1, PW CROUS 2 and BD WINGFIELD3

1Tree Pathology Co-operative Programme, Forestry and Agricultural Biotechnology Institute (FABI), Department of Microbiology and Plantpathology, University of Pretoria, Pretoria, 0002, Republic of South Africa; 2Department of Plant Pathology, University of Stellenbosch, Stellenbosch, 7602, Republic of South Africa; 3 Department of Genetics, University of Pretoria, Pretoria, 0002, Republic of South Africa

Background and objectives
The anamorph genus Leptographium is well known to forest pathologists and includes both pathogens of trees and species commonly associated with sap stain of lumber. Most species of Leptographium are closely associated with insects and particularly bark beetles (Coleoptera: Scolytidae) that act as their vectors. We recognise these fungi as anamorphs of Ophiostoma that contain cellulose and rhamnose in their cell walls, and that are able to tolerate high levels of the antibiotic, cycloheximide in culture [1, 2].

Throughout its taxonomic history, the genus Leptographium has been associated with several different, but morphologically similar genera. The first of these, Scopularia, described in 1851, was synonymised with Leptographium in 1927 because the characters reported for the former genus could not be verified [2]. Verticiciadieiia and Phialocephaia, two genera described in the Leptographium complex, were distinguished from Leptographium based on differences in conidium development. These differences were later shown not to be taxonomically reliable and Verticiciadieiia was reduced to synonymy with Leptographium. Those anamorphs of Ophiostoma, thought to represent Phialocephaia spp., have subsequently been accommodated in Leptographium . Species of Leptographium are morphologically similar and notoriously difficult to distinguish from one another. The lack of an effective key to species has contributed to difficulties in identifying these fungi. In many cases, the Ophiostoma state has been described with only a brief mention of the anamorph. In culture, the Leptographium state is predominant and a teleomorph is seldom found. Forest pathologists are commonly faced with the dilemma of having to identify Leptographium species based on poor descriptions and incomplete data. These problems have emphasised the need to re-evaluate Leptographium and to compile a comprehensive key to described species.

Materials and Methods
Isolates of all known species of Leptographium were grown on 2 % malt extract agar. Living cultures, as well as herbarium collections, were studied using ight and/or scanning electron microscopy. Relevant structures of all species were measured and illustrated photographically and through the use of line drawings.

Results and conclusions
Comparisons were made with the original descriptions as well as type specimens for each Comparisons were made with the original descript were compiled. Names were provided for species previously only known through their connection to an Ophiostoma state. A complete list of all hosts and insects associated with Leptographium spp. was compiled, and dichotomous as well as a synoptic keys to species, were constructed. With the aid of these keys, species presently known in Leptographium can now be accurately identified.

References
1. Wingfield MJ, 1993. Taxonomy, Ecology and Pathogenicity. (ed. MJ Wingfield. KA Seifert & JF Webber). American Phytopathological Press, St. Paul, Minnesota, pp 43-51.
2. Harrington, TC & Cobb, FW (Jr.), 1988. Leptographium root diseases on conifers. American Phytopathological Society Press, St. Paul Minnesota, pp 150.