Archivio Journal of Plant Pathology

Abstract:

Circular or irregularly shaped necrotic spots with yellow border, present on ca. 30% of the leaves were observed in 2010 on pomegranate trees (Punica granatum) cv. Wonder- ful in an orchard in Thessaloniki (northern Greece). Single- spore cultures from the fungus isolated on PDA gave rise to white colonies which turned to grayish-black and produced obclavate, obpyriform or ellipsoidal conidia in long chains. Conidia had 1 to 6 transverse and 0 to 3 longitudinal septa and measured 9.4-30.8×5.6-15.4 μm (average 20.1×10.7 μm). These morphological characteristics conform to those of Alternaria alternata (Fr.) Keissl. (Simmons, 2007). The ITS1- 5.8S-ITS2 region was amplified with primers ITS1 and ITS4 and sequenced (GenBank accession Nos KT900855- KT900859). A BLAST search of GenBank database revealed 100% homology with the sequences of various A. alternata isolates (e.g. KR149266). Spraying leaves of 10 healthy green- house-grown pomegranate plants (cv. Wonderful) with a 106 spores/ml spore suspension resulted in the production, 20 days post inoculation, of leaf spots similar to those observed in the field. Control plants sprayed with sterile distilled wa- ter remained symptomless. A. alternata was reisolated from artificially inoculated leaves fulfilling Koch’s postulates. Al- though A. alternata has been reported to cause fruit rot on pomegranate in Greece (Tziros et al., 2008) this is the first report of A. alternata causing a foliar disease on this host.