Archivio Journal of Plant Pathology

Abstract:

Pomegranate (Punica granatum L.) is an emerging crop in Italy, particularly in Apulia region, where more than a third of fruits is produced. In 2016, rot symptoms were observed on the fruits of cv. Wonderful One in local markets and in a packinghouse in the province of Lecce, with an incidence of ca. 5%. Symptoms consisted of circular creamy-brownish lesions, centrally darker, with tissue softening. A fungus was isolated by plating marginal rotted tissue fragments from surface-sterilized (2% sodium hypochlorite) fruits on semi-selective potato dextrose agar (PDA). Plates were incubated at 24°C in the dark. Colonies were whitish, turning olive green and dark brown at maturity. Globose and dark brown pycnidia (250-500 µm) covered the mycelium after 14 days. Conidia were 4-6×1-2 µm in size, allantoid, hyaline, and aseptate. These characteristics corresponded to those of Cytospora punicae Sacc. (Saccardo, 1884). The ITS1-5.8S-ITS2 region (accession No. KY496629) proved 100% identical to a C. punicae sequence from GenBank (KJ621687). To fulfill Koch’s postulates, five surface-sterilized pomegranate fruit of cvs Acco and Wonderful One were wounded with a 5-mm-cork-borer at two opposite sides along the equatorial axis, and inoculated with mycelial plugs from 14-day-old PDA cultures. Sterile plugs were used as controls. Fruit were incubated as above. Symptoms were visible only on inoculated fruit, and after 14 days, pycnidia appeared. Fruits of cv. Acco proved to be the most susceptible. Cytospora punicae was re-isolated only from inoculated pomegranates. Although reported as a rot agent of pomegranate plants (Samouel and Kanetis, 2016) and recently fruits in South Africa (Venter et al., 2017), to our knowledge, this is the first report of C. punicae causing postharvest rot on pomegranate fruit in Italy.