VIEW ARTICLE

Postharvest Pathology and Mycotoxins

Population Dynamics of Erwinia carotovora and Pectolytic Clostridium spp. in Relation to Decay of Potatoes. M. C. M. Pérombelon, Visiting Professor, Department of Plant Pathology, University of Wisconsin-Madison, Madison, 53706, Present address of senior author: Scottish Horticultural Research Institute, Invergowrie, Dundee DD2 5DA, Scotland, U. K.; J. Gullings-Handley(2), and A. Kelman(3). (2)(3)Research Specialist, and Professor respectively, Department of Plant Pathology, University of Wisconsin-Madison, Madison, 53706. Phytopathology 69:167-173. Accepted for publication 31 August 1978. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-167.

Three pectolytic strains of Clostridium spp., in addition to Erwinia carotovora var. carotovora (Ecc) and E. carotovora var. atroseptica (Eca), were present in samples of potato stocks in Wisconsin. Type L (white) and LP (pink), were strongly pectolytic obligate anaerobes with subterminal oval spores; type S (white) was weakly pectolytic and micro-aerophilic with round terminal spores. Types L and LP were more pathogenic (based on the effective median dose [ED₅₀] for induction of visible decay in injected tubers) than type S. Under anaerobic conditions strains of E. carotovora grew faster in tubers and were more pathogenic at 16 C than were type L clostridia; however, at 20–22 C Eca and Ecc were as pathogenic as type L. Furthermore, Eca was more pathogenic than Ecc at 16 but not at 20–22 C. When Eca and type L clostridia were injected together in tubers and incubated under anaerobic conditions at 16 C, the former organism became the dominant component of the population in the decayed tissue; however, at 20 C the clostridia tended to predominate. Rotting was induced in tubers by clostridia alone; furthermore Erwinia-free tubers derived from stem cuttings could be induced to rot if clostridia were present. Onset of decay however, was accelerated especially at 16 C if strains of E. carotovora were present.