Short report: The first report of round leaf spot disease of sugar beet caused by Cercospora beticola in Kermanshah province

Cercospora leaf spot with the fungal agent Cercospora beticola is one of the most important diseases of sugar beet in many countries of the world including Iran (Dabbagh et al. 2015). According to research conducted in many countries, cercospora leaf spot disease not only affect the quantity of sugar beet production but also have a negative effect on the quality characteristics of the crop such as sugar content and its constituent compounds (Dabbagh et al. 2015; Khan et al. 2007). The results of a study showed that in addition to reducing photosynthesis, the cercospora leaf spot disease causes a decrease in sugar and the amount of amino acids with the increase of phenolic substances, and has a negative effect on the process of producing sugar as the final product of sugar beet, as well as on root weight, sugar yield and raw syrup purity (Yoshimura et al. 1992). In Iran, this disease has been reported from Khuzestan, the shores of the Caspian Sea, Ardabil, Urmia, Khoy, Bojnord, Bandar Abbas and Kazerun (Eeshad 1995). In Khuzestan province, the level of contamination in some years, especially in early planting dates has been observed up to 50 and 80% in commercial and susceptible cultivars, respectively (Dabbagh et al. 2015). The most important symptom of cercospora leaf spot disease includes more or less circular spots, which spreads on old leaves and covers the whole leaf. Epidemic occurs rapidly and complete leaf senescence occurs (Jacobsen and Fran 2009). During the visit and inspection of sugar beet fields in Kermanshah province, no signs of cercospora round spot disease were observed. In August 2023, during a visit to the sugar beet fields located in Gowdin region of Kangavar county, the symptoms of this disease were observed on BTS and Salama cultivars. After transferring samples to the laboratory and preliminary evaluations in order to isolate the pathogen, the parts of the infected leaves with disease symptoms that contained C. beticola fungus spores were rinsed with sterile water and the obtained spore suspension was spread on 1.5% water-agar medium. After the spores germinated, one germinated spore was transferred to the culture medium (Potato Dextrose Agar) PDA (Abbasi et al. 2004). After the necessary evaluations based on the formation of conidiophores on the stromal tissue on the infected spots, the shape of the progeny on the culture medium and the measurement of the conidiophores and conidia, the fungi species C. beticola was identified by comparing with reliable scientific sources (Fig. 1) (Chand et al. 2013). . It should be noted that cercospora leaf spot caused by C. beticola is usually observed in relatively hot and humid areas, but in this study, the disease was observed in the easternmost part of Kermanshah province in a relatively cold and dry area. This is the first report of Cercospora leaf spot disease of sugar beet caused by C. beticola from Kermanshah province.