Previous View
APSnet Home
Phytopathology Home


Physiology and Biochemistry

Heat- and Aging-Induced Tolerance of Sorghum and Oat Tissues to Host-Selective Toxins. Charlotte R. Bronson, Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824; Robert P. Scheffer, Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824. Phytopathology 67:1232-1238. Accepted for publication 24 March 1977. Copyright 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-1232.

Intact sorghum seedlings were held at high temperatures (37/30 C, day/night) and the roots were exposed to host-selective toxin from Periconia circinata. After 4 days, the plants had no visible symptoms, whereas toxin-treated plants at 22 C were dead. Assays based on net electrolyte losses from tissues showed that intact plants given brief thermal treatments were highly resistant to toxin, and that full sensitivity was regained within 3 days. Excised sorghum leaves pretreated in water at 35, 40, and 45 C for 15, 4.5, and 0.8 min had 50% as much toxin-induced loss of electrolytes as did controls exposed to water at 22 C. Prior thermal treatments also prevented toxin-induced increases in tissue respiration. Inoculated plants failed to develop symptoms at 37/30 C. Within 3 hr after excision, sorghum leaves at 22 C had 50% as much toxin-induced leakage of electrolytes as did freshly-cut leaves, and by 24 hr excised leaves leaked very little in response to toxin. Toxin sensitivity of excised sorghum leaves was maintained by treatment with kinetin (104M). Excision and aging did not reduce sensitivity of oat leaves to toxin from Helminthosporium victoriae, although sensitivity was lost after thermal treatments; longer exposure times or higher temperatures were needed to reduce toxin-induced losses in oats than in sorghum. The data are useful for design of toxin assays and may contribute to an understanding of the seasonal development of Periconia blight.