Analysis of ecotype × location interaction in cold-region alfalfa ecotypes

To study the yield stability and to select superior cold-region alfalfa ecotypes, this study was conducted with 17 ecotypes at 13 research stations in 2005-2008 growing seasons. For each location, a randomized complete block design with three replications was used. For further analysis and undesrtanding an AMMI analysis (additive main effects and the multiplicative interaction effects) was employed. The ecotypelocation interaction was significant. Based on dry forage yield (65.6%) and plant height (67.7%) of the sum of squares of ecotype×location interaction were explained by the first two interaction principal components. Biplot of the two first principal components and AMMI stability value on 17 ecotypes and 13 locations showed that Sadaghian ecotype was the most stable ecotype and Malekandi and Mohajeran had the highest dry forage yield. For plant height, Gharehaghaj ecotype was the most stable and Galebani had the tallest plant height. Ecotypes with high and stable dry forage yield were identified in each location.