Calonectria species, including four novel taxa, associated with Eucalyptus in Malaysia

Abstract

The genus Calonectria accommodates many important pathogens of agricultural, horticultural and forestry crops, including Eucalyptus. During 2017 surveys of Eucalyptus diseases in Sabah, Malaysia, typical symptoms of Calonectria leaf blight were observed. A large number of Calonectria isolates were collected from diseased leaves and soils associated with symptomatic trees. The aim of this study was to identify and resolve the phylogenetic relationships between these isolates using morphological characters and DNA sequence comparisons for six gene regions. From a collection of 73 isolates, eight species residing in three species complexes were identified. Amongst these, four undescribed species were characterized and are named here as Ca. borneana, Ca. ladang, Ca. pseudomalesiana and Ca. tanah. Results of this study support the view that planted Eucalyptus in tropical and subtropical areas of the world represent niches remarkably rich in Calonectria spp. This also has implications for the management of diseases on these important trees.