Differentiation of species of Elsinoë associated with scab disease of Proteaceae based on morphology, symptomatology, and ITS sequence phylogeny
Scab disease of Proteaceae, which was initially observed on Leucospermum in South Africa in 1981, has subsequently been reported on this host from Australia and Hawaii. The disease, commonly known as corky bark or scab, is associated with severe losses of commercial plantings of Leucospermum in South Africa, and has also been collected from species of Leucadendron, Protea and Serruria in South Africa, from Banksia, Leucadendron, Mimetes, Protea and Serruria in Australia, and from Leucospermum and Protea in California and Zimbabwe. The causal agent was determined to be a species of Elsinoë, which has not been formally described. The aim of the present study was to elucidate the taxonomy of the species of Elsinoë associated with scab disease of Proteaceae in these countries. Morphology, symptomatology and DNA sequence analysis of the 5.8S rDNA gene and its flanking ITS1 and ITS2 regions were used. Anamorph and teleomorph characteristics of isolates from Leucospermum, Protea and Banksia suggest that there are at least four distinct species involved. These findings are strongly supported by the phylogenetic tree inferred from DNA sequence data. Furthermore, these results also show that the Elsinoë isolates from Leucadendron, Leucospermum and Serruria in South Africa and Australia, and the isolates from Leucospermum in California and Zimbabwe are representative of the same species.