FIRST REPORT OF PLEOSPORA TARDA CAUSING LEAF SPOT OF LEPIDIUM DRABA IN IRAN

Abstract

Since 2009, leaf spot symptoms were observed on Lepidium draba (whitetop) an invasive weed collected in wheat plots (Triticum sp.) in the Hamadan Province of Iran. Typical symptoms included chlorosis of the basal leaves with black discrete ascomata protruding from the leaf surface. Colonies of a fungus recovered from diseases leaves were brown to olivaceous with a white aerial mycelium in the center. Since the morphological characters of this mycete were consistent with the description of Pleospora tarda (Simmons, 1985), its identification was confirmed by amplifying and sequencing the internal transcribed spacer region (ITS) of a representative isolate (GenBank accession No. KC660992). To fulfill Koch’s postulates, a spore suspension (105 ascospores/ml) of the fungus was sprayed onto leaves of whitetop seedlings at the 4-6 leaf stage. Inoculated seedlings were maintained in a growth chamber at 25°C, with more than 75% relative humidity and a 12 h light photoperiod. Inoculated plants showed symptoms like those observed in the field 14 days post inoculation. P. tarda was reisolated from inoculated plants and a culture was deposited in the Iranian Research Institute of Plant Protection with the accession code IRAN 2184C. To our knowledge, this is the first report of P. tarda infecting whitetop in Iran and in the world.