Exploring the Morphological Traits and the Physiology of Yield Formation in Dominant Barley (Hordeum vulgare L.) cultivars in Temperate Zone and Gamma-irradiated Improved Barley, in Iran

An experiment was conducted at the experimental field of Agricultural Research Institute of Atomic Energy Organization in Karaj in 2015, as a randomized complete block design with three replications. Treatments included 14 barley cultivars . Results showed that there were significant differences between most of the studied barley cultivars regarding physiological and morphological traits. The newer cultivars and Roudasht showed advantages over older cultivars with regard to leaf area index, radiation use efficiency and crop growth rate. Cultivars Valfajr, Makouee and Bahman had the highest leaf mass fraction, mostly as a result of being late-maturity cultivars along with having high leaf area index and specific leaf area. On the other side, cultivars Behrokh, Roudasht and Makouee had the highest stem mass fractionmainly as a result of their corresponding growth habits (two-rows, gamma- irradiated and tall- statured, respectively). Also results showed that cultivars which had the highest stem and leaf mass fractions such as Makouee, Roudasht and Valfajr produced the lowest spike mass fraction and in turn grain yield. Cultivars Lout, Nosrat, Rayhann03 and Fajr30 had the highest spike mass fraction which could be attributed to their six-row habit of spike, early-maturity and lower leaf and stem dry matter at flowering stage. Overall, it could be concluded that tall statured late-maturity cultivars along with gamma- irradiated improved barley cultivar had the highest leaf and stem mass fractions compared to dwarf and early maturity cultivars. Such advantage, however, translated into lower spike mass fraction and grain yield of the former group.