First report of leaf spots caused by Phoma sorghina on clover (Trifolium campestre) in Turkey

During disease surveys carried out in 1999-2001 (Sert, 2002), severe spots were found on clover leaves (Trifolium campestre; Fabaceae), growing in the Antalya province of southern Anatolia, Turkey. The symptoms began as small, circular, white spots on both lower and upper leaf surfaces. The circular spots increased in size (between 1-2 mm in diameter), developing into irregular lesions, which were pale brownish in colour. Microscopic examination of the spots revealed the presence of pycnidia (70-200 µm wide) on both the lower and upper leaf surfaces. Leaves showing symptoms were disinfected (1 min in 70% ethanol, 2 min in 1% NaOCl), plated onto malt extract agar and incubated at room temperature. Colonies grew rapidly (attaining a diameter of 61 mm after 5 days) and were grey-green to salmon-pink in colour. Pycnidia produced hyaline, ellipsoid simple conidia (4.5-6 x 2-2.5 µm) (Fig. 1). No chlamydospores were observed. The fungus was consistently isolated on malt extract agar and identified as Phoma sorghina based on the morphological characteristics seen (White & Morgan Jones, 1983).

Pathogenicity tests were conducted on 3-month-old clover plants, by spraying unwounded leaves with a conidial suspension (2x106 spores per ml.). Control plants were sprayed with sterile water. Inoculated and control plants were enclosed in transparent plastic bags and incubated at 22-24°C for 3 days with a 12-h photoperiod. The bag was then removed. Two weeks after spraying leaf lesions developed on inoculated plants and P. sorghina was consistently re-isolated. No disease symptoms were observed on control plants. The pathogen has been reported on many plant species in the world (Farr et al., 2004) but not on clover. This is the first record of P. sorghina on T. campestre in Turkey.