Identification of Mycosphaerella species associated with Eucalyptus nitens leaf defoliation in South Africa

Eucalyptus nitens is an important plantation tree species in South Africa, where it is grown for paper and pulp production. The growth and performance of E. nitens in South Africa is, however, reduced substantially by Mycosphaerella leaf blotch (MLB) disease. The aim of this study was to determine which species of Mycosphaerella are associated with MLB epidemics on E. nitens in the KwaZulu-Natal Province of South Africa. Mycosphaerella species were isolated from leaves from two commercial E. nitens plantations by inducing the active release of ascospores onto agar. All isolates were identified according to their ascospore germination patterns, anamorph associations and sequence data generated from the Internal Transcribed Spacer region of the rDNA operon. From taxonomic and sequence data, M. nubilosa was identified as the main cause of MLB on E. nitens in commercial plantations in the KwaZulu-Natal Province. M. nubilosa is an important Eucalyptus leaf pathogen, and its correct identification in South Africa is important for the future planting of E. nitens. This is particularly true during the initial years of tree growth where MLB results in severe defoliation.