Variability of Different Characteristics of Field Resistance in Different Alfalfa (Medicago sativa L.) Genotypes to Alfalfa Weevil (Hypera postica Gyll.)

Alfalfa weevil is a major pest in parts of Iran and the world that alfalfa is grown. The damage would be decreased using resistant varieties. In the study of the field resistance of 42 genotypes of alfalfa in the germplasm cultivated in research farm of Bu-Ali Sina University towards this pest, it was found that different genotypes had significant effects on the number of larva, amounts of damage, status of chlorophyll, and the yield of fresh forage yield and on the other traits too. In the stepwise regression for the amounts of damage as dependent variable it was revealed that number of larvae, plant height in damage time and the percent of dried matter were respectively added to the model and confirmed the percentage of the most variations with the cumulative contrast coefficient of 30.48%. In the analysis into principal components, approximately 59 percent of the total variation was explained by the first two principal components. Selection based on the first component leads to the selection of high performance genotypes and selection based on the second component leads to the selection of genotypes with high resistance to larval feeding. Five clusters were induced after cluster analysis. Genotypes Fayez 49 with low resistance and high forage yield and Tack Buteh 23 with high resistance and low forage yield could be used as appropriate parents for hybridization in plant breeding.