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This article in CS

  1. Vol. 19 No. 1, p. 75-78
     
    Received: June 28, 1978


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doi:10.2135/cropsci1979.0011183X001900010017x

Temperature Tolerance in Soybeans. I. Evaluation of a Technique for Assessing Cellular Membrane Thermostability1

  1. J. R. Martineau,
  2. J. E. Specht,
  3. J. H. Williams and
  4. C. Y. Sullivan2

Abstract

Abstract

The effect of temperature on yield of soybeans (Glycine max (L.) Merr.), is often underestimated despite reports of a significant relationship between yield and growing season temperatures. The identification of genotypes having heat tolerance appears to be warranted, but a simple, rapid technique for measuring tolerance to high temperature is needed. A technique previously used for assessing genotypic differences in membrane thermostability (heat tolerance) in sorghum (Sorghum bicolor (L.) Moench) was evaluated for use in soybeans. The technique involves the measurement by electrical conductance of the amount of electrolyte leakage from heat-damaged leaf tissue cells after exposure to elevated temperatures. The relationship between the degree of injury and the temperature at which that injury was induced was observed to be a sigmoidal response. Genotypic differences in heat tolerance were associated with differences in the relative position of the response curve with respect to the treatment temperature. Greatest sensitivity in detecting genotypic differences occurred at temperatures inducing about 50% injury. Genotypic differences were greatest in newly developed leaf tissue. Consequently, only the most recently developed leaves should be used in the assay. Plant-to-plant variation was appreciable and necessitated the use of bulked leaflets from several plants as samples. Genotypic differences were consistent across sampling dates, indicating that the assay can be conducted during any phase of vegetative growth. Results obtained from cultivar trials over several years show significant differences among genotypes and consistent relative ranking of genotypes in different environments. Although requiring replication to achieve a sufficiently small standard error, the technique shows promise as a screening method.

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