First report of leaf necrosis and wilt of rosemary induced by Cladosporium herbaroides in Iran.

Abstract

In Spring 2013, wilted and collapsed rosemary (Rosmarinus officinalis) plants were found in a greenhouse in the Hamedan province of Iran. Disease symptoms consisted of wilting and leaf necrosis followed by death. Leaf fragments from the edge of leaf lesions were surface- sterilized in 5% NaOCl for 60 sec. Eight-day-old cultures were subcultured on synthetic nutrient agar (SNA) at room temperature (23± 2°C). Morphological observations (Bensch et al., 2012) showed that conidiophores were both macro- and micronematous and branched in a few cases. Macronematous conidiophores measured 30-230×3-5 μm and micronematous conidiophores were 3-65×2–3 μm. Conidia formed by macronematous conidiophores were catenate, subglobose, obovoid, limoniform, ellipsoid to cylindrical, 3-33×3-6 μm size and 0-3 septate. Conidia formed by micronematous conidiophores were paler and narrower, mostly formed in unbranched chains, limoniform, narrowly fusiform, almost filiform to subcylindrical, 15-31×2-3 μm in size and 0-3 septate. A portion of the translation elongation factor 1-α (TEF) gene was PCR-amplified using primers EF1-526-F and EF1-156-R (Bensch et al., 2012) and sequenced. The TEF gene sequence was 99% similar to that of C. herbaroides (accession No. KM052582). Pathogenicity was tested by spraying a conidial suspension (1x105 spores/ml) in sterile water on healthy leaves of 2- to 3-week-old greenhouse-grown rosemary plants. Control plants were sprayed with sterile water. Symptoms appeared two weeks post inoculation on inoculated plants whereas control plants remained asymptomatic. The same fungus (C. herbaroides) was reisolated from inoculated plants, thus fulfilling Koch’s postulates. To our knowledge, this is the first report of C. herbaroides on rosemary in Iran.