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Partial Characterization and Use of a Host-Specific Toxin from Helminthosporium sacchari on Sugarcane. Gary W. Steiner, Associate Pathologist, Genetics and Pathology Department, Experiment Station, Hawaiian Sugar Plantersí Association, Honolulu, Hawaii 96822; Ralph S. Byther, Associate Pathologist, Genetics and Pathology Department, Experiment Station, Hawaiian Sugar Plantersí Association, Honolulu, Hawaii 96822. Phytopathology 61:691-695. Accepted for publication 22 January 1971. DOI: 10.1094/Phyto-61-691.

Toxic filtrate was obtained from 20- to 24-day-old cultures of Helminthosporium sacchari, the causal agent of eye spot disease of sugarcane. Partial purification of the toxic compound was accomplished by treating concentrated filtrate with methanol (soluble), partitioning with chloroform (insoluble) and butanol (soluble), and fractionating by gel filtration (Sephadex G-15). The toxin was stable over extended periods of time and to heat of up to 144 C. Toxin production and fungus growth were affected by both temperature and time. Symptoms produced by the toxin and the fungus are similar. Only plants susceptible to the fungus are affected by the toxin. The toxin reaction of 182 sugarcane clones was significantly correlated (r = .88) to their reaction to the pathogen. Large-scale screening for resistance to eye spot disease can be accomplished accurately and rapidly by using this toxin.