PHYLOGENY AND MORPHOLOGY OF NEODIDYMELLIOPSIS IRANENSIS SP. NOV., CAUSING DEAD BRANCHES OF CITRUS IN IRAN

Abstract

Citrus plants, which are mostly cultivated in the southern tropical area of the country, are one of the important economic crops in Iran. Branch canker and dieback of citrus is an ongoing problem for citrus growers located in these areas and has imposed irreparable damage to the citrus production in this region in recent years. Disease symptoms consisted of the blight of vigorously growing shoots and dieback of the branches and rootstock trunks. This study aimed to characterize the citrus dieback pathogen morphologically and phylogenetically, and the species Neodidymelliopsis iranensis Soleimani & Goudarzi, sp. nov., is described and illustrated here. Isolates were derived from collected citrus samples with dieback symptoms. After preparing pure cultures from single spores on oatmeal agar and malt agar, the morphological features of the species were described and their pathogenicity was confirmed on lime (Citrus aurantifolia). Morphologically N. iranensis is easily separated from the other species of Neodidymelliopsis by the size of pycnidia, conidia septation, and NaOH test results. The morphological differences between our isolates and the other known species of Neodidymelliopsis were strongly supported by a multi-locus phylogenetic analysis based on the ITS region, and LSU, RPB2, and TUB2 genes. In the reconstructed phylogenetic tree, N. iranensis formed a well-supported clade with other Neodiddymelliopsis species in the Didymellaceae family, but was separated from all other Neodiddymelliopsis species. The distinct phylogenetic position is supported by differences in morphological features. Consequently, the specificity of the morphological and phylogenetical features of the collected isolates has convinced us to describe Neodidymelliopsis iranensis as a new species.