In order to determine the relationship between grain yied, main developmental stages, morphological structures and yield components, 500 bread wheat lines obtained from Iranian Cereal Collections were evaluated in an augmented design with four checks and 20 blocks in 1994. Measurements were made on days to flowering, days to physiological maturity, grain filling period, flag leaf length, flag leaf width, flag leaf area, length of flag leaf sheath, extrusion length, peduncle diameter, spike length, plant height, grain yield, biological yield, harvest index, kernels per spike, 1000 kernel w’eight, spikelets per spike, fertile spikelets, florets per spikelet, fertile florets per spikelet and spikes per plot. The data were analyzed by calculating simple correlation coefficients and by using stepwise regressions and factor analyses. Correlation coefficients of yield with all the traits except spike lenght, peduncle diameter and grain filling period was significant.The effectiveness of grain yied and biological yield from spike lenght and peduncle diameter was also observed in regression models. In factor analysis, the factor of grain filling period was considered as the only significant coefficient and 6.6 percent of total variation was accounted for by this coefficient in factor-5. The final results showed that all three methods had an emphatic and complementary role in determining the relationship between grain yield and related cha’racters, while the factor analysis had a preferable results.
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