Identification and characterization of Alternaria alternata (Fr.) Keissler causing Ceratonia Blight disease of carob (Ceratonia siliqua L.) in Turkey

Abstract

Carob (Ceratonia siliqua L.) leaves showing suspected symptoms of Ceratonia Blight disease were collected from both wild and domestic carob plants at various locations in the province of Antalya in Turkey. The fungus growing on culture medium started as white-grayish airy mycelium at the margin with clear light to dark green inner zonation radiating from a common center. Dark brown conidia in chains were observed ranging in sizes from 5 to 35 μm. The conidia surface was smooth to verruculose, slightly constricted with 4–6 transverse septa; the lower part of each portion had one or two longitudinal septa. The conventional PCR was conducted based on the beta tubulin gene and ITS region, which resulted in fragment sizes of 184 bp and 346 bp, respectively. The amplified PCR products were sequenced aligned and BLAST analysis showed 100% homology for the two genes with other strains from the GenBank nucleotide database. The isolates also tested positive with SYBR Green fluorescence dye using Real-Time PCR. The results of the disease incidence recorded across the fields ranged from 10 to 100% on both wild and domesticate carob plants. The putative pathogen was pathogenic on the inoculated carob plants and was consistently re-isolated from the symptomatic plant leaves and thereby satisfying the Koch’s postulates. Based on our knowledge, this is the first report implicating Alternaria alternata for causing Ceratonia Blight disease in Turkey.