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Resistance

Population Dynamics of Erwinia carotovora pv. carotovora in Potato Stems. M. K. Rahimian, Graduate research assistant, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706; J. E. Mitchell, professor, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706. Phytopathology 74:217-220. Accepted for publication 6 September 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-217.

Inoculum (2 103 cfu per plant) of Erwinia carotovora pv. carotovora micropipetted into a potato stem at a leaf axil increased logarithmically in the stem tissue of potato cultivar Norgold Russet, but increased less rapidly in similarly inoculated Russet Burbank potato plants. The population of a weakly virulent strain increased less rapidly than that of a highly virulent strain that caused rapid death of the plants. This weakly virulent strain caused only slight necrosis at the point of inoculation when inoculum of 2 107 cfu per plant was used. In infectivity titration tests, specific inoculum doses ranging from 108 to 102 cfu per plant were injected at a leaf axil of each plant by means of a capillary pipette. Probit analysis of quantal responses (number of stems showing soft rot) of potato cultivars to the highly virulent strain gave ED50 values of 1.27 105 for the susceptible Norgold Russet and 1.36 107 for the more resistant Russet Burbank. A soil strain, serogroup XXIX, was less virulent than a highly virulent strain isolated from a potato stem.