19 BİTKİ KORUMA BÜLTENİ 2008, 48(4): 19-33 Erzurum-Pasinler Ovası’nda ayçiçeğinde Sclerotinia sclerotiorum ve S. minor tarafından oluşturulan gövde çürüklüğü hastalığının yaygınlığı, etmenlerin tanılanması ve bazı ayçiçeği çeşitlerinin hastalık etmenlerine reaksiyonu 1 Elif TOZLU 2 Erkol DEMİRCİ 3 SUMMARY Incidence and characterization of sunflower stem rot disease caused by Sclerotinia sclerotiorum and S. minor in Pasinler Plain of Erzurum, and reaction of some sunflower cultivars to the pathogens This study was conducted in Pasinler Plain of Erzurum Province. Two-hundred- thirty-two isolates of Sclerotinia spp. were obtained from infected plant stems in 1999-2001. Characterization of these isolates indicated that 73% belonged to Sclerotinia sclerotiorum and 27% to S. minor. Sclerotium sizes of S. sclerotiorum and S. minor isolates were 5.1-11.0 x 3.8-6.2 mm and 1.0-3.0 x 0.1-0.8 mm, respectively. Apothecium formation were observed in S. sclerotiorum isolates, and ascospors were in monomorphic structure. However, apothecium was not developed in S. minor isolates. Nine of the mycelial compatibility groups (MCGs) were identified among the 68 isolates of S. sclerotiorum. Four of them were single-member of MCGs, wheras the remaining MCGs comprised 4-28 isolates each. On the other hand, no MCGs were determined for S. minor isolates. It was found that palmitic, linoleic and oleic fatty acids were predominated in mycelia of all tested S. sclerotiorum and S. minor isolates. The incidence of Sclerotinia stem rot on sunflower plants was determined 4.5% in 2001 and 7.3% in 2002 in this area. Field inoculation tests revealed that S. sclerotiorum isolates were more virulent than S. minor isolates. Fifteen sunflower cultivars were determined to be sensitive against these pathogens at various degrees. Key words: Mycelial compatibility group, reaction of cultivar, Sclerotinia sclerotiorum, Sclerotinia minor, sunflower 1 Bu makale doktora çalışmasının bir kısmından hazırlanmıştır. 2 Doğu Anadolu Tarımsal Araştırma Enstitüsü, 25090 Erzurum. 3 Atatürk Üniversitesi, Ziraat Fakültesi, Bitki Koruma Bölümü, 25240 Erzurum. Yazının Yayın Kuruluşuna geliş tarihi (Received): 13.03.2009