Archivio Journal of Plant Pathology

Abstract:

Alfalfa (Medicago sativa) is a perennial flowering plant in the pea family Fabaceae, cultivated as an important forage crop in many countries around the world including Iran. During a survey in spring and summer of 2016, symptoms of leaf spots on M. sativa were observed in an area of more than 20 ha in Hamadan province, Iran. It was estimated that 50-60% of plants were damaged by this disease. Leaf spots were small, dark brown, 0.3- 0.5 cm in diameter. Small pieces of infected tissues were taken from the margins of spots and after surface-disinfection, they were transferred to Potato Dextrose Agar (PDA) at 25°C. The isolates were purified and were transferred onto Oat Meal Agar (OA). On this medium aerial mycelium consisting of subhyaline, branched, septate, smooth, 2–3 µm wide hyphae, produced globose to subglobose, dark brown to black pycnidia. Conidia were hyaline, smooth to punctate, 1-celled, and cylindrical to subcylindrical, straight with rounded apex and truncate base, and measured 12-20 × 3-5 µm. Morphological characteristics of our isolates were in agreement with the description for Chaetopyrena penicillata (Arzanlou and Khodaei, 2012). Pathogenicity tests were performed three times. Medicago leaves were sprayed with conidial suspension (1×106 spores/ml), while control plants were sprayed with sterile distilled water Symptoms were reproduced 10 days after inoculation and C. penicillata was consistently reisolated from artificially infected plants only, To confirm the morphological identification, the internal transcribed spacer regions (ITS1, ITS2, and 5.8s gene) of rDNA were amplified with the primers ITS1/ITS4 and sequenced (White et al., 1990). The sequence was deposited in GenBank (Accession No. KY681683) and BLAST search showed 99% similarity with sequence belonging to C. penicillata (JQ663990.1). To our knowledge, this is the first report of leaf spot caused by C. penicillata on M. sativa in Iran.