Crop cultivars development with high grain yield is the principle goal in bread wheat. In spite of that, the efficiency of each breeding program mainly depends on quality, direction and magnitude of the association between grain yield with other traits involved in grain yield formation and the relative importance of them. For this purpose, twelve cultivars and landraces of bread wheat (Triticum aestivum L.) were evaluated for seventeen characters. The result of simple correlation coefficient analysis indicated a significant positive association between grain yield with harvest index, biological yield, the number of spike per square meter and negative association with time to heading. Association between grain yield with harvest index and biological yield were also obtained through regression analysis using stepwise method. By using factor analysis, seventeen variables were defined in four factors explaining 84 percent of total variations. The first factor considered as yield factor confirmed the effective role of harvest index and biological yield each on grain yield again. The second factor considered as yield components factor, indicated negative correlation between the number of spike with kernel’s characteristics in each spike namely kernel weight and kernel number, which was in
accordance with the results which has obtained from simple correlation coefficient analysis. Path
analysis indicated direct positive effect of biological yield, the number of spike per square meter, the number of kernel per spike, plant height and spike length each on grain yield. Overall, our observations showed the harvest index and biological yield as important traits in selection of high yielding bread wheat varieties. Furthermore, the number of spike per square meter was the most important yield component and plant height was important morphological trait determining the grain yield, seemingly, selection of these two traits may contribute to increase in grain yield. Also, the reversed reciprocal effect of the number of kernel per spike on other traits involved in grain yield, explained limited success in improvement of bread wheat that has been pointed out by other researchers.