VIEW ARTICLE

Etiology

Identification and Distribution of Races C1 and C2 of Cercospora beticola from Sugarbeet. E. D. Whitney, Plant Pathologist, Agricultural Research Service, U. S. Department of Agriculture, U. S. Agricultural Research Station, Salinas, California 93901; R. T. Lewellen, Geneticist, Agricultural Research Service, U. S. Department of Agriculture, U. S. Agricultural Research Station, Salinas, California 93901. Phytopathology 66:1158-1160. Accepted for publication 1 April 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1158.

On the basis of differential cultivar reactions, 14 sugarbeet isolates of Cercospora beticola from California, Colorado, Maryland, and Texas were classified as either physiological race C1 or C2. Race C2 occurred in California and Maryland, and race C1 was collected from all four states. Although the races could not be distinguished by morphological or cultural characteristics, there were large differences among isolates in length of conidia and conidiophores. Isolates reacted differentially on water agar, sugarbeet leaf extract agar, and sugarbeet leaves. In some cases, conidia and conidiophores lengths were longer on one medium than on another; whereas on other media, they were shorter. Thus there was a highly significant isolate × growth media interaction. In general, race C2 isolates were more aggressive on the susceptible cultivar than were race C1 isolates.