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Ultrastructure of Cells in Toxin-Treated and Helminthosporium sacchari-Infected Sugarcane Leaves. Gary A. Strobel, Professor, Department of Botany and Microbiology, Montana State University, Bozeman 59715; W. M. Hess(2), and Gary W. Steiner(3). (2)Professor, Department of Botany and Range Science, Brigham Young University, Provo, Utah 84601; and (3)Associate Pathologist, Hawaiian Sugar Planters Association, P.O. Box 2450, Honolulu, Hawaii 94804. Phytopathology 62:339-345. Accepted for publication 19 October 1971. DOI: 10.1094/Phyto-62-339.

Helminthosporium sacchari is the causal agent of eye spot disease of sugarcane, and produces a host-specific toxin, helminthosporoside. In this study, resistant and susceptible clones of sugarcane were treated with helminthosporoside and with helminthosporoside-14C for varying periods, then examined by electron microscopy and radioautography. Cells from fungal-infected leaves and from leaves of a susceptible clone treated with the toxin varied from showing virtually no alteration of the cytoplasm to its complete disruption. Furthermore, the cytological alterations seen in fungal infected tissues greatly resembled those observed in susceptible tissues treated with helminthosporoside. Abnormalities in the ultrastructure of chloroplasts in susceptible sugarcane were the earliest cytological disturbances that could be attributed to the action of helminthosporoside. In leaves of a resistant clone treated with the toxin, the chloroplasts and other organelles generally were not damaged. Helminthosporoside-14C was recovered from the same area of the leaf that was examined by electron microscopy, indicating that the toxin was present in the area of the leaf showing cytological abnormalities.