Possible heat‐tolerant wheat cultivar improvement through the use of flag leaf gas exchange traits in a Mediterranean environment

Abstract

AbstractBACKGROUND: Flag leaf traits are associated with performance of wheat (Triticum aestivum L.) genotypes in heat‐stress environments. Fifteen cultivars were evaluated during 3 years with two sowing dates under irrigated conditions so as to examine the relationship between the flag leaf traits and performance in a Mediterranean environment.RESULTS: It became possible to assess a heat susceptibility index (HSI) for each cultivar by altering the sowing date, exposing the crops to different temperatures. The cultivars showed significant differences for all measured traits except canopy temperatures and chlorophyll fluorescence, though not all were consistent. Excluding two cultivars that differed in development, yield, grain number, harvest index and leaf An (net CO2 assimilation rate), gs (stomatal conductance to water vapor), mc (apparent mesophyll conductance of CO2) and ash content were negatively associated with HSI, whereas leaf area and width were positively associated. Traits showing the best correlation with HSI were An, followed by area, gs, mc, width and ash content. High An was associated with smaller leaf size.CONCLUSION: It is worthwhile to select high ear grain number and harvest index. In addition, flag leaf gas exchange traits and ash content can be used as complementary selection criteria after the possible pleiotropic associations of these traits with leaf size are clarified. Copyright © 2008 Society of Chemical Industry