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In order to evaluate the relationship between different traits of grain yield in durum wheat, 20 durum wheat (Triticum durum Desf.) landraces selected from the northwest of Iran together with five controls were evaluated under normal and drought stress conditions. Environmental mean squares were significant for all the traits studied except for harvest index which showed that drought stress has significant effect on all the traits. In normal condition, fertile tillers, peduncle length, spike length, number of grain spike and harvest index had the most positive direct effect on yield, while under drought stress condition, biological yield and harvest index had the most positive direct effect on yield. In regression analysis (stepwise method) in normal condition, infertile tillers and 1000 grain weight remained in the final model (R2 = 0.485), while under stress condition, Fv/Fm, Fm and biological yield remained in the final model (R2 = 0.667). Factor analysis of the total five factors was used to determine 76.708 and 77.128% of the data changes and adjustments in normal irrigated and drought stress conditions, respectively. The multiple statistical procedures used in this study showed that harvest index and biological yield were the most important yield variables to be considered under drought conditions. So, these traits could be used as selection criteria for increasing yield.
Key words: Durum wheat, drought stress, chlorophyll fluorescence, chlorophyll content, multivariate analysis.