Determination of Interrelationships Among Phenotypic Traits of Iranian Fennel (Foeniculum vulgare Mill.) Using Correlation, Stepwise Regression and Path Analyses

Iran is known, as a main producer of Fennel. Fifty genotypes of Fennel (Foeniculum vulgare Mill.) from different part of Iran were collected and some phenotypic traits were studied with these main objectives (1) evaluate phenotypic diversity among Iranian fennel populations; (2) compare essential oil content and seed yield among populations originating from different ecological areas; (3) determine possible correlations between essential oil and seed yield with phenotypic traits. Genotypes of Meshkin shahr, Moqan and Fozve showed a high range (273-395 g/m(2)) of seed yield, while high essential oil content was detected in genotypes Fozve, Kashan, Givi, Marvdasht and Kaleibar (3-3.6 cc/100 g dry matter). Correlation and causal relationships among 26 phenotypic traits were determined. Seed yield and essential oil content were used as dependent variables in a stepwise regression model to determine predictor variables. Direct and indirect effects of each independent variable were calculated using path analysis. Stepwise regression showed that weight of dry biomass, harvest index, days to 50 % flowering, number of leaves, length of peduncle and number of tillers accounted for 55.58, 39.4, 1.57, 1.14, 0.43 and 0.2 % respectively, of the variations in seed yield. Also, stepwise regression showed that the number of leaves, length of peduncle and weight of dry biomass and length of the middle internodes accounted for 27.14, 11.91, 7.11 and 3.66 % respectively, of the variations in essential oil content. The residual effects in the present study were estimated to be 0.1694 for seed yield and 0.7079 for essential oil content model. Totally for seed yield improvement, positive selection for the weight of dry biomass and harvest index and negative selection for day to 50 % flowering are recommended and for the essential oil improvement, selection of weight of dry biomass, length of peduncle and length of middle internodes with negative effect can be done. In conclusion genetic diversity of Iranian fennel populations as shown in this study should play a critical role in future selection and breeding programs.