FIRST REPORT OF PHOMA ALIENA CAUSING FRUIT ROTS OF POMEGRANATES IN NORTHERN GREECE

Abstract

Pomegranate fruits rot is a very important disease with a worldwide distribution. In November 2012, pomegranate fruits showing rapidly enlarging brown lesions were observed in Vrontou (Prefecture of Pieria, Greece), from which isolations were made on acidified- PDA (2.5 ml 85% lactic acid per litre of medium). Plates incubated at 23oC for a week yielded colonies with a dark mycelium and abundant black, globose pycnidia 70 to 300 μm in diameter. Hyphae were septate and conidia were hyaline, one-celled, ellipsoid to ovoid (average 5-11x2-4 μm). Pathogen identification was based on morphological characteristics and sequencing of the ITS4/5 region (ca. 700 bp long) which was aligned with comparable fungal sequences using MEGABLAST. The highest homology (99%) was found with Phoma aliena (GenBank accession No. KC311486). For pathogenicity tests 20 mature fruits of cv. Wonderful were disinfected by dipping in 10% sodium hypochlorite for 15 min prior to inoculation, whereby 6 mm wide holes were made on the fruit peel in which an agar disk of the same size, excised from a fungal colony, was placed. Inoculated fruit were enclosed in plastic containers and incubated for a week in a growth chamber at 24-26°C. Control fruits were inoculated with agar discs without mycelium. A fungus identical to that used for inoculation was re-isolated from symptomatic fruits, fulfilling Koch’s postulates. Species of the genus Phoma such P. lycopersici, P. destructive, P. exigua were reported as the agents of fruit rot on tomatoes and eggplants (Kubota et al., 2000; Laundon, 1971). To our knowledge, this is the first report of the occurrence of P. aliena causing fruit rot of pomegranates in Greece and worldwide.