Genetic Analysis of Path Coefficients of Some Traits in Relation with Tolerance to Alfalfa Leaf Weevil (Hypera postica Gell.)

Alfalfa, as a fodder plant in Hamedan, is attacked by alfalfa leaf weevil (Hypera postica Gell.). In this study, 76 alfalfa populations in the germplasm of Bu-Ali Sina University farm were investigated randomly. Traits SPAD, number of larvae, percentage of damage, height of the plant in the time of damage and harvest, percentage of dry matter, and traits of the dry and fresh yield of forage were studied in this research. The results showed that there is a correlation between the number of larvae trait and damage percentage (r = 0.733**), SPAD and damage percentage (r = 0.292*), forage yield and plant height at the time of damage (r = 0.512**), dry fodder yield and plant height at the time of damage (r = 0.314**), the yield of wet and dry fodder (r = 0.754), the percentage of dry matter with the yield of fodder (r = 0.316**), and the dry yield of fodder with the percentage of dry matter (r= 0.332**). Step-by-step regression for the wet yield of fodder as a function variable showed that traits of the dry yield of fodder, percentage of dry matter, and plant height in the damage stage were entered into the model, respectively, and justified the most changes in fodder performance with a cumulative explanation coefficient of 93.53%, while other studied traits had no significant effect on the model.  According to the entered traits (forage dry yield traits, dry matter percentage, and plant height in the damage stage) in the regression model, path analysis was done to determine causal relationships affecting. Path analysis of traits under study on wet forage yield revealed that it had the most direct and indirect effects on dry forage yield and matter percentage, respectively. This result was confirmed by the high correlation between wet fodder yield and dry fodder yield.