植物病理学与微生物学杂志

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Phylogenetic Analysis of Alternaria species Associated with Citrus Black Rot in Iran

Shideh Mojerlou and Naser Safaie

Citrus black rot caused by Alternaria spp. is significant post harvest problem in Iran. The causal agent of black rot was originally identified as A. citri by Ellis and Pierce. The genus Alternaria circumscribes considerable morphological diversity and citrus black rot may be caused by more than one morphospecies in addition to A. citri. Morphological identification of small-spored Alternaria spp. is difficult. Phylogenetic analysis was performed on 7 small-spored Alternaria isolates from black rotted citrus fruit in Iran using sequence data from an anonymous locus, OPA10-2. Samples were collected from navel oranges in Mazandaran province in the north of Iran. All isolates caused black rot in a fruit inoculation assay with Navel and Valencia oranges and significant differences were observed between
cultivars and among isolates. No association was found between morphological classification and phylogenetic clade. We identified A. tenuissima (ALT 6) as the causal agents of citrus black rot. Two isolates (ALT8 and ALT9) grouped together, separately from other clades in most parsimonious trees. It suggested that both of them belong to different species. This is the first report of molecular characterization of citrus-associated Alternaria species in Iran and A. tenuissima is reported as the causal agent of citrus black rot in Iran for the first time.