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Identification of Fusarium oxysporum f. sp. cubense Race 4 from Soil or Host Tissue by Cultural Characters. E. J. Sun, Graduate Research Assistant, Plant Pathology Laboratory, National Taiwan University, Taipei, Taiwan, Hilo, HI 96720; H. J. Su(2), and W. H. Ko(3). (2)Professor, Plant Pathology Laboratory, National Taiwan University, Taipei, Taiwan, Hilo, HI 96720; (3)Professor, Department of Plant Pathology, University of Hawaii, Beaumont Agricultural Research Center, Hilo, HI 96720. Phytopathology 68:1672-1673. Accepted for publication 24 April 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1672.

Fusarium oxysporum f. sp. cubense race 4 formed laciniated colonies distinct from those of races 1 and 2 on modified Komada’s medium (K2 medium) but not on potato-dextrose agar, PCNB agar, Martin’s medium, or surfactant agar. Race 4 was detectable by the laciniated colonies recovered from infected host tissue, and also directly from soil on dilution plates. All isolates of F. oxysporum obtained from 55 wilted Cavendish banana trees susceptible only to race 4 formed laciniated colonies on K2 medium. None of the isolates obtained from 16 wilted Latundan banana trees susceptible only to race 1 formed laciniated colonies on the same medium. Six formae speciales of F. oxysporum, one saprophytic F. oxysporum and three other species of Fusarium tested did not form laciniated colonies on K2 medium. The recovery of race 4 from experimentally infested soil was about 90% using K2 medium. The population of race 4 in naturally infested soil, determined with K2 medium, ranged from 50 to 650 propagules per gram of air-dried soil.