Abstract

Grain yield in wheat, similar to other plants, is a complex trait that is directly and indirectly influenced by other plant’s characteristics. One of the main goals in wheat breeding programs is to increase the grain yield.Considering the role of crop rotation in the increase of wheat yield, in order to study variations in direct and indirect effects in different rotations, an experiment was conducted with six rotation types as treatments, in six replications, as randomized complete block design. The six rotation types included: wheat-wheat-wheat (without rotation), wheat-canola-wheat, wheat-chickpea-wheat, wheat-cotton-wheat, wheat-watermelon-wheat and wheat-sunflower-wheat. This study was implemented during 2004 to 2009 in the north of Iran, at the research station of Gonbad in Golestan province of Iran. Also, at the end of trial, wheat was cultivated in all experimental units in 2010. The results showed although in all the rotations, the spike numbers in m², kernel number per spike and kernel weight were important traits determining grain yield, crop rotations affected on type and amount of direct and indirect effect of yield components. Furthermore, the selection of different traits depending on the rotation’s condition can change in the selection. According to the results in wheat-wheat-wheat (without rotation) and wheat-watermelon-wheat and wheat-sunflower-wheat rotations, kernel weight, grain filling periods and vegetative period are useful for selection breeding strategy, while in wheat-canola-wheat and wheat-chickpea-wheat number kernel per spike, number spike, grain filling periods and vegetative period could be useful.

Key words: Breeding, grain yield, path analysis, selection.