Biochemical genetic studies on genotype strains of medfly, Ceratitis capitata (Wied.)

Four genotypes of Mediterranean fruit fly (medfly), i.e. two laboratory strains (dark and yellow pupae), genetic sexing line and wild strain were examined biochemically in larvae, pupae and adult stages by means of isoelectrophoresis to determine further genetic variations. Isozymes of alkaline phosphatase, polyphenol oxidase and esterase enzymes were chosen for study. The medfly genotypes exhibited variations in the strains, as well as the genetic sexing line according to the biological characters. In order to identify some markers to distinguish individuals of different strains it should prove necessary to compare the electrophoretic pattern mobilities of isozyme numbers and activities of the three tested enzymes. The isoenzymes were genetically different from one genotype to another and from one stage to another. These results appear to be consistent over polymorphic loci. The functional genes of alkaline phosphatase larvae were higher in band numbers and activities than those of pupae and adult extractions in all materials. No variations were found between the adult males and females of all materials except the males of the genetic sexing line, which were more active. Electrophoresis and spectrophotometer enzymatic analysis of polyphenol oxidase indicated that the larval stage was more active than the other stages. In addition, the larval polyphenol oxidase activity of the yellow pupae strain and the genetic sexing line were more active than the others. Concerning the esterases, the genes controlling the activity of isozymes were different from one strain to another according to the stages of development. The esterases band numbers were low in larvae, but a high number was found in adult males of the genetic sexing line and the females of the yellow pupae strain. The results of this work were supported by previous results of Sabrah et al., where the genic polymorphism and ontogenic variation of esterase isoenzymes in medfly collected from different geographical zones in Egypt was studied