Morphological and Phylogenetic Insights Into <i>Calonectria acuminata</i> sp. nov., a New Pathogen Causing Leaf Blight of <i>Eucalyptus</i> in India

ABSTRACT This study describes Calonectria acuminata sp. nov. from the blighted leaves of Eucalyptus in India, using a polyphasic approach. This species is distinguishable from the currently recognised 140 Calonectria species by its unique, multiple tapered stipe extensions. Analyses of the combined partial actin , calmodulin , histone , rDNA internal transcribed spacer, translation elongation factor‐1α and β‐tubulin regions revealed a distinct phylogenetic position for this new taxon within the Calonectria cylindrospora species complex. The pairwise homoplasy index test also supported the hypothesis of a new species. This species caused foliar disease symptoms on Eucalyptus camaldulensis and was successfully reisolated, thereby fulfilling Koch's postulates. These findings emphasise the need for extensive disease surveys in northern India, which are essential for studying the diversity of Calonectria fungi. This approach has significant implications for managing foliar diseases caused by these pathogens on Eucalyptus and other important trees.