Archivio Journal of Plant Pathology

Abstract:

In March of 2012 a survey was conducted to determine the incitant of papaya (Carica papaya) scab disease in the Hamedan province of Iran. Symptoms consisted of pale green and water-soaked lesions on leaves. A fungus was consistently isolated from diseased tissues on potato dextrose agar (PDA) at 23± 2°C. Morphological observations were carried out on Synthetic Nutrient Agar (SNA) medium as described by Bensch et al. (2012). Conidiophores were macronematous or semimacronematous. Ramoconidia (15-50 × 2.5-5 μm) were straight and cylindrical with up to three septa. Small terminal conidia (3-6 × 1.5-2.5 μm) were subglobose to ovoid and aseptate. Intercalary conidia (5-12× 2-4 μm) were ellipsoid to ovoid and aseptate. A portion of the translation elongation factor 1-α gene was amplified (Bensch et al., 2012) and sequenced (GenBank Accession No. KP998105). A BLAST search showed 99% similarity with GenBank sequences belonging to C. cladosporioides. Pathogenicity tests were conducted in a greenhouse at 25°C. Inoculum was prepared by rinsing a 7-day-old culture on PDA with sterile water and adjusted to 106 spores/ml. Three papaya seedlings (cv. Horng-Fe) were sprayed with the spore suspension and covered with plastic bags for three days, while control treatments were sprayed with sterile water. Symptoms appeared five days post inoculation on all inoculated seedlings and C. cladosporioides was consistently reisolated, whereas control seedlings showed no symptoms. To our knowledge, this is the first report of C. cladosporioides causing papaya scab in Iran.