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Resistance

Chemical Desiccation of Wheat Plants as a Simulator of Postanthesis Speckled Leaf Blotch Stress. Miriam Zilberstein, Department of Botany, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978; A. Blum(2), and Z. Eyal(3). (2)Division of Field Crops, The Volcani Center, ARO, P.O. Box 6, Bet-Dagan, Israel; (3)Department of Botany, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978. Phytopathology 75:226-230. Accepted for publication 29 June 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-226.

Field trials were conducted over 2 yr to evaluate whether the postanthesis destruction of the photosynthetic source by chemical desiccation may be used to detect wheat cultivars that sustain kernel growth in the presence of speckled leaf blotch. Spring wheat cultivars of diverse origin were subjected to three treatments: inoculation with virulent isolates of Septoria tritici until an epidemic was initiated, postanthesis application of magnesium chlorate (4% a.i.) solution to destroy most of the plant's green tissues, and a control in which a fungicide was applied to protect against loss of green tissue. Grain yield components, kernel growth curves, and harvest index were determined. The progress of the pathogen on the four uppermost leaves was monitored at weekly intervals. For similar Septoria progress values (area under the disease progress curve), various cultivars manifested different rates of loss in kernel weight (as percent of the fungicide-treated control), and harvest index. Cultivars differed in the rate of loss in kernel weight and harvest index when treated with the chemical desiccant. Significant correlations were revealed across the same five cultivars in losses in kernel weight between plants infected by S. tritici and those that had been chemically desiccated in 1 yr (r = 0.925) but not in the other (r = 0.804). Correlation between the two parameters was highly significant (r = 0.626) across 16 (out of 18) cultivars that had similar Septoria progress values. The correlations in losses in kernel weight between plants infected by S. tritici and those that had been mechanically defoliated (postanthesis) in the five cultivars in 1981-1982 were r = 0.733. The potential for utilizing post-anthesis chemical desiccation as a measure for revealing wheat cultivars tolerant to speckled leaf blotch in the absence of infection by S. tritici is discussed.