Present status of citrus blast disease in Cukurova region in Turkey

Abstract: Citrus blast disease, caused by Pseudomonas syringae pv. syringae, in 1991, had a severe outbreak in Erdemli, is a province of Mersin, in the eastern of Mediterranean region of Turkey and so far, the blast disease got a great importance in this region. Characteristic disease symptoms were first seen on leaves as watersoaked lesions and black areas on the petiole wings. Later, lesions extended to the mid-vein of leaves and to the twigs surrounding the base of the petiole. Finally, the leaves dried and rolled, while still firmly attached, before eventually dropping without petioles. The necrotic areas on twigs further enlarged and the twigs were eventually killed within 20-30 days. We investigated the disease susceptibility of the most cultivated citrus plants in the region. Of the citrus varieties, Citrus limon cvs. Lamas, Enterdonate and Kutdiken were tolerant; C. paradisi cvs. Mars Seedless and Red Blush were less susceptible; C. sinensis cvs. Yafa, Valencia and Washington Navel, C. reticulata cvs. Clementine, Fremont, Satsuma and Mineola Tangelo, C. paradisi cv. Star Ruby were found the most susceptible varieties in citrus plants. In 2004, the disease appeared again and caused economically significant losses in C. sinensis cvs. Washington Navel and Marisol. Many strains isolated from damaged petioles, wings and leaves of citrus trees. Eight years later, the new outbreak, in 2012, the disease symptoms has observed in C. reticulata cvs. Nova and Okitsu, C. sinensis cv. Washington Navel and C. paradisi cv. Star Ruby. Since 1991, according to observations, it is supposed that environmental conditions and citrus varieties have a great role on disease development in the region. Pathogen can cause severe outbreaks on susceptible citrus plants just after warm and raining spring time. Additionally, in last years, many stone fruit plantations were established in the region, and, also well known that the pathogen can damage those plants. Our further studies will be focused on newly introduced citrus varieties and those stone fruit plantations.