Determining the Relation of Traits in TwoMentha spicataL. Populations from Iran, by Path and Principal Component Analysis

: To determine the relationships of essential oil yield with flowering shoot yield, morphological traits and essential oil percentage of two Mentha spicata populations, this six year experiment was conducted at the Research Institute of Forests and Rangelands, Tehran, Iran, from 1999 to 2004. The experiment was conducted as split plot in time in the form of a randomized complete block design with three replications and two factors: population (from Tehran and Yazd, Iran) as the main factor and year (six years of the plant growth) as the sub factor. Analysis of the variance indicated that for all traits were significant differences among years. For most of the traits there were also significant differences between two populations. Results of Pearson correlation showed that the total essential oil yield was significantly correlated to all other traits except for leaf width and flower essential oil percentage. Stepwise regression analysis indicated that leaf essential oil yield, flower essential oils yield, the number of lateral branches, flower essential oil percentage and stem diameter contributed to more than 96 % of the variations. Path analysis revealed that leaf essential oils yield had the highest positive direct effect (0.76) on the total essential oils yield. Finally, principal component analysis indicated that three components contributed to more than 90 % of the variations.