Disease Note.

Two New and Unusual Dry Rots of Stored Potatoes in Greece. C. C. Thanassoulopoulos, Aristotelian University, Faculty of Agriculture, Plant Pathology Laboratory, P.O.B. 269, 540 06 Thessaloniki, Greece. E. Giapanoglou, Aristotelian University, Faculty of Agriculture, Plant Pathology Laboratory, P.O.B. 269, 540 06 Thessaloniki, Greece. Plant Dis. 78:924. Accepted for publication 29 April 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0924A.

In a market survey of potato tubers for postharvest fungal diseases, two unusual and not seriously damaging cases of dry rots were noticed, both from mountainous potato-growing areas in Nevrokopi and Vrondou of northern Greece. These rots involved the tuber flesh up to a depth of 10 mm. From a total of 2,500 tubers examined, 1.73 and 1.33% of each rot was found, respectively, without any association with other pathogenic or saprophytic organisms. In the first case, a yellow-orange mycelium was detected on the rotted area. The fungus had a yellow-orange, floccose colony, abundant verticillate conidiophores characteristic of the genus Verticillium, black microsclerotia, and hyaline chlamydospores. It was identified as Veriicillium tricorpus I. Isaak (2). In the second case, black mycelium of a fungus developed on the rotted areas. The colony of the fungus was grayish black and floccose with simple, erect conidiophores bearing phialide-like, conidiogenous cells. The fungus was identified as Phialophora parasitica Ajello, L.K. Georg, and Wang (1). Pathogenicity tests were performed with each fungus on each of 26 wounded and unwounded tubers by superficial inoculation with a small colonized agar piece. A polyester cylindrical cup (20 mm diameter and 20 mm high) containing moistened hydrophilous cotton was affixed over each inoculated site for at least 3-4 days, and tubers were placed al room temperature (15-24 C) for 40 days. Disease was evident to a depth of 15-20 mm into the flesh of wounded tubers only. Isolations from three depths at each rotted site were positive for 25 tubers inoculated with V. tricorpus and from 26 tubers with P. parasitica. Isolations from unwounded tubers and from noninoculated controls were all negative. This is the first report for both tuber rots and for the occurrence of the fungus V. tricorpus in Greece.