Distribution of a devastating fungal pathogen in mangrove forests of southern Iran

Abstract

An epidemic of canker and dieback was found on Avicennia marina (Forssk.) Vierth and Rhizophora mucronata Lam. in the mangrove forests located in three different regions (the Qeshm Island, Sirik Port and Khamir Port) of Hormozgan province, on the southern coast of Iran, Persian Gulf. For A. marina, the highest mean of disease incidence was estimated in the Sirik Port (60.6%), followed by the Qeshm Island (50.4%) and Khamir Port (45.2%). Based on a dieback ordinal rating scale from 0 to 5, disease severity had the highest mean in the Sirik Port (3.1), followed by the Qeshm Island (2.7) and Khamir Port (2.5). The species R. mucronata was more affected by the disease than A. marina with the mean disease incidence of 62.5% and the mean disease severity of 3.2. A fungus was consistently recovered from the symptomatic tissues which was identified as Neoscytalidium dimidiatum based on morphological and molecular studies. Phylogenetic analysis of partial nucleotide sequence of the internal transcribed spacer (ITS) region (ITS1–5.8S-ITS2) validated the identity of the putative pathogenic fungus. Koch's postulates were fulfilled using healthy detached branches of both mangrove species inoculated with mycelium plugs of N. dimidiatum. This study is the first report worldwide concerning the occurrence of canker and dieback on A. marina and R. mucronata caused by N. dimidiatum.