Journal of Plant Pathology Archive

Abstract:

A new disease of globe artichoke (Cynara scolymus), affecting ca. 50% of the edible portion, was observed during 2011 in Peloponnese (southern Greece). On flower buds, symptoms started as small concentric dark-brown sunken spots, later coalescing and covering the entire surface of the buds, which rotted completely. Single-spore cultures on potato dextrose agar (PDA) gave rise to white colonies which turned to grayish-black and produced verrucose, echinulate or smooth conidia in long chains. Conidia had 1 to 6 transverse and 0 to 2 longitudinal septa and measured 10.4-26.0x7.8-15.6 μm (average 18.1x10.1 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 No. KT071541). BLAST search revealed 100% homology with sequences of various A. alternata isolates (e.g., LN835252). Twenty healthy detached artichoke buds were sprayed with a spore suspension (106 spores/ml), covered with a polyethylene bag for 48 h and incubated in a growth chamber at 25oC. Ten days post inoculation, spots similar to those observed in the field developed on all inoculated buds, while control buds sprayed with sterile water remained symptomless. A. alternata was consistently reisolated from inoculated buds. Alternaria sp. has been reported on globe artichoke in Brazil, California, Mexico and South Africa (Farr and Rossman, 2015). This is the first report of A. alternata as the cause of bud rot on C. scolymus in Greece.