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Pathological Changes in Ultrastructure: Effects of Victorin on Resistant Oat Roots. Harry Wheeler, Professor, Department of Plant Pathology, University of Kentucky, Lexington 40506; Phytopathology 61:641-644. Accepted for publication 4 January 1971. DOI: 10.1094/Phyto-61-641.

Oat roots, resistant to victorin, were exposed for periods of 4, 10, and 20 hr to solutions which contained 200 units of victorin/ml. In roots exposed for 4 hr and fixed in KMnO4, cortical cells had densely stained walls, hypersecretory Golgi dictyosomes with densely stained vesicles, and more or less parallel profiles of the endoplasmic reticulum. These features, which are not found in the cortex of non-treated roots, are similar to those described in susceptible roots exposed to much lower concentrations of victorin. In resistant roots treated with victorin for 4 hr, a few individual cells or isolated groups of 2-4 cells were severely disrupted, with only mitochondria recognizable as relatively intact organelles. These disrupted cells were similar to severely damaged exterior cells of victorin-treated susceptible roots. Resistant roots treated with victorin for 10 and 20 hr showed the same effects as those treated for 4 hr, except that some had unusually large Golgi vesicles and a few cells completely disrupted, with not even mitochondria recognizable. Cell wall lesions which are abundant in susceptible roots treated with victorin were not found in treated resistant roots. These results are consistent with physiological data, which indicate that at high concentrations, victorin induces in resistant tissues many of the changes found in susceptible tissues exposed to very low concentrations of this pathotoxin.

Additional keywords: Helminthosporium victoriae.