First Report of Ascochyta fabae on Sainfoin Turkey

Sainfoin (Onobrychis viciifolia Scop.) is one of the most commonly grown forage crops in Erzurum, Turkey. During the summer of 2000 and 2001, a serious disease with typical blight symptoms was observed in sainfoin fields in the province of Erzurum, Turkey. Initial symptoms on leaves were more or less circular, slightly sunken with a definite margin, and usually dark brown with a lighter centre in which pycnidia developed (Figs. 1 and 2).

Stem lesions were elongated, sunken and darker in colour than leaf lesions (Fig. 3) with scattered pycnidia. Small black pycnidia that produced a pink exudate containing hyaline, straight, slightly truncate at the base and rounded at the apex, 1-3 septate (rarely 3 septate), 13 to 24 µm (average 18.1 ± 0.32 µm) x 4 to 6 µm (average 5 ± 0.06 µm) conidia under high humidity were visible in the centre of the spots. The fungus was consistently isolated on potato dextrose agar from diseased leaves or stems, and identified as Ascochyta fabae Speg. based on morphological characteristics of pycnidia and conidia (Ellis & Ellis, 1985).

To satisfy Koch’s postulates, a conidial suspension (1.7 x 10⁶ conidia per ml) of the fungus was sprayed onto leaves and stems of sainfoin seedlings (15 weeks old) (cv. Erzincan). Both inoculated seedlings and control seedlings (inoculated with sterile water) were covered with plastic bags for 72 h in a glasshouse at 23 ± 2°C. Inoculated plants showed characteristic symptoms of Ascochyta blight 12 – 15 days after inoculation. The fungus was reisolated from lesions that developed on the leaves and stems of all inoculated plants but not from tissues on any of the control plants. The pathogen has been recorded previously on sainfoin in Iran, in 1996 (Sharifnabi & Fatehi, 1996). This is the first report of Ascochyta fabae on sainfoin in Turkey.