R. Milani

Genetic variability and gene flow in geographical populations of Ceratitis capitata (Wied.) (medfly)

Two African populations of Ceratitis capitata (Kenya and Réunion Isl.) and two Mediterranean ones (Sardinia and Procida Isl.) have been studied for genetic variability at 25 loci by electrophoresis. Wright’s FST, Slatkin’s Nm* gene flow estimator, Nei’s distance (D) together with measures of variability such as [Hmacr ], [Pmacr ], Ā have been used to compare the population from Kenya with the other three. Parameters using gene frequencies (FST, D, Nm*) indicate the presence of substantial geographic heterogeneity, largely attributable to genetic drift and correlated with dispersion of the medfly from its source area (Subsaharan Africa) to the periphery. The Kenyan population has high genetic variability (assessed by [Hmacr ], [Pmacr ] and Ā), as might be expected given its native status. Significant gene flow estimates between Kenya and the derived Mediterranean populations supports the hypothesis of recent colonization. Part of the geographic heterogeneity is related to the presence of fixed alleles in the more differentiated Réunion population although it maintains the genetic attributes of the ancestral population. Selection or other forces may have played an important role in the differentiation of this population.

Spatial and temporal differentiation in colonizing populations of Ceratitis capitata

Two ancestral populations (Kenya and Reunion), two Mediterranean (Procida and Sardinia) and one new American population (Guatemala) of Ceratitis capitata were examined by electrophoresis for genetic variability at 27 enzyme loci. Two ordination approaches (principal component analysis and a tree representation) and F-statistical analysis have been used to distinguish the various patterns of genetic variations and to infer the underline causes and their relative contribution to the total variation. Three main patterns of variation emerge from the data: geographical, annual and seasonal differentiation. A main part of intraspecific variability involves the differentiation of central (Kenya and Reunion) versus peripheral populations (the Mediterranean and the American populations). The analysis suggests that the genetic structure of these populations is correlated with the historical events of their colonization. The affinity of the Guatemalan population with the Kenyan one could be the result of a recent founding of this population from the source area (Africa). More ancient historical events of colonization characterize the two Mediterranean populations. Seasonal variation has been found in the Procida population and chiefly involves the Mpi locus. In the same population the genetic variation across years has a minimum in 1986 due to the release of sterile T-101 males.

Evidence for a genetic duplication involving alcohol dehydrogenase genes inCeratitis capitata

AnAdh duplication is described in the medflyCeratitis capitata. Evidence is presented for two separateAdh1 andAdh2 structural loci mapping at a distance of 0.49 recombination unit from each other. By deletion mapping theAdh region has been cytologically located near the free end of the left arm of the second chromosome within an area between 2C;3A segments of the polytene chromosome. The genetic analysis of the region aroundAdh has identified seven neighboring genes (Acon1,Mpi, Est6,Aox, Xdh, Mdh2,LspI) which identify the linkage group D. The orientation of loci with regard to the centromere sets the origin of the map of the left arm of the second chromosome close to the twoAdh loci.

Recenti sviluppi delle ricerche genetiche sulla mosca domestica

Summary Linkage has been detected among three genes of M. domestica including kdr (DDT - Resistance), originally found in nature. The evidences so far produced by different workers on the inheritance of resistance suggest that the capacity of resisting high doses of insecticides can be a simple genetic character as well as a very complex one; all the evidences for multifactoriality (or polygeny) derive from laboratory selected strains tested with methods based on dosage/effeet correlations. Toxicological tests on several samples of wild flics collected in different points of a distriet periodically submitted to routine sprayings show that two quite distinet levels of tolerance can be found in each population; these levels are the same found in laboratory experiments involving susceptible and kdr resistant strains. The relative frequency of resistant and susceptible individuals differ between local populations.

Genetical approach to systematics and phylogeny of Trypetinae (Diptera, Tephritidae)

Abstract Genetic variation at 25 enzyme loci (64 alleles) has been considered in the attempt of an intra‐species analysis of Ceratitis capitata. Twenty‐seven hortologous loci (122 alleles) were selected to elucidate the relationships among Ceratitis capitata, Ceratitis rosa, Trirhithrum coffeae and Capparimya savastonoi of the Trypetinae subfamily. Two ordination approaches have been used for electrophoretic data: Principal Component Analysis (PCA) and cluster analysis through a tree representation. At the species level, for C. capitata ordination by means of PCA enabled the geographic and seasonal intraspecific differentiation to be recognized. At higher levels of taxonomy, when applied to species and genera, PCA has been used as an alternative to cluster analysis. Nei distance and UPGMA procedure have been used in both levels of systematic ordination. For species‐genera level, genetic distances have been calculated using also Rogers, Cavalli and Edwards methods (UPGMA and Wagner procedure). The cophenet...

6-phosphogluconate dehydrogenase in the housefly, Musca domestica L.:evidence for inheritable 6PGD polymorphism.

Two electrophoretic variants of the 6-phosphogluconate dehydrogenase (6PGD) enzyme have been found in the WHO/IN/Musca domestica/1 housefly laboratory strain. The patterns shown by Cellogel zone electrophoresis can be fully explained by the hypothesis of two codominant autosomal alleles. On this hypothesis, a specific Pgd locus has been postulated and the symbols PgdA and PgdB have been assigned to the two alleles causing the PGD-A and PGD-B phenotypes. The bands corresponding to the homozygous phenotypes PGD-A and PGD-B have different electrophoretic mobility and staining intensity; they can be described, respectively, as “fast-weak” and “slow-thick.” The heterozygous phenotype PGD-AB gives a three-banded pattern, indicative of a dimeric structure for this enzyme; this pattern is asymmetrical. Heterozygous flies have been found both among wild-type strains of recent colonization and among old established laboratory colonies. Most strains are PgdB monomorphic; up to now only three strains have been PgdA monomorphic, all of them being multimarker strains. The Pgd locus has been traced to the housefly linkage group III.

Map position of Aldox (aldehyde-oxidase) and Adh (alcohol dehydrogenase) loci on autosome II of Musca domestica L.

The Aldox and Adh structural loci of Musca domestica L. belong to autosome II. They code for the enzymes aldehyde oxidase and alcohol dehydrogenase. Both these enzymes have allelic variants with specific electrophoretic mobility, which, on cellogel, are seen as single bands. The Aldox and Adh loci encompass a large map interval, which includes the morphological markers ar, cm, and car. The recombination frequencies between these five loci indicate the alignment Aldox – ar – cm – car – Adh.

6-phosphogluconate dehydrogenase activity variants inMusca domestica L.: A further allele at thePgd locus as proved by densitometric assay

A new electrophoretic variant of 6-phosphogluconate dehydrogenase (6PGD) has been detected in flies of a laboratoryMusca domestica strain. This variant is to be added to the two already described, PGD-A and PGD-B, identified by a fast-weak and a slow-thick electrophoretic band, respectively. The new variant, PGD-C, has the same mobility as PGD-A but provides a more intensely stained band; therefore it can be described as a fast-thick phenotype. The staining intensity of PGD-C is slightly lower than that of PGD-B. Genetic and densitometric tests have shown that the different levels of enzymatic activity of the two fast variants A and C are inherited as alternative genetic units, and they have been interpreted as one aspect of the phenotypic expression of twoPgd alleles, namely,PgdA andPgdC. These alleles determine both the rates of electrophoretic mobility (fast in both cases) and the levels of activity (low for A, strong for C; shown by weak or thick stained electrophoretic bands). Similarly, the two distinctive features of PGD-B, namely, slow mobility and high activity level, are always jointly inherited and appear as two pleiotropic aspects of the phenotype coded for by thePgdB allele. ThePgdB/PgdC heterozygous flies provide a slightly asymmetrical three-banded zymogram, while thePgdA/PgdC combination leads to a single-banded pattern, showing the same mobility as the parents and an intermediate staining intensity. The quantitative analysis of enzyme activity of 6PGD zymograms, performed through densitometric methods, has led to the recognition of three different activity levels coded for byPgd alleles, one of which, namely,PgdC, would not have been detected using electrophoretic methods alone.

Spontaneous occurrence of brown and waltzer mutants in Rattus norvegicus

Abstract An adult male Rattus norvegicns, with a greyish‐brown sandy colour, similar to the mutant brown associated with the normal agouti’ allele, was trapped near Pavia in the year 1958. In 1960 we started a line by crossing this unusual animal with an albino female. After several years (in 1987), the progeny of these crosses produced a female affected by motor disorder corresponding to the description of the mutant waltzer. The close correspondence of the observed phenotypes with brown and waltzer suggest alle‐lism between the mutants responsible; however a direct test to confirm allelism was unfeasible. The origin of the mutants, their observed phenotypic properties and inheritance and, with regard to waltzer, degree of penetrance, are here reported.

Electrophoretic study of some enzymatic genes in Musca domestica L.

Abstract Cellogel electrophoresis has been used to study isocitrate dehydrogenase (IDH), malate dehydrogenase (MDH), malic enzyme (ME), and alcohol dehydrogenase (ADH), in the housefly. Two forms of MDH (MDH, and MDH2) have been separated. These show properties similar to those ascribed to supernatant and mitochondrial MDH enzymes in other organisms. In the housefly zymograms of the mitochondrial fraction show MDH2 activity only. Allelic variants of MDH1 differing in thermostability and resistance to p‐hydroxymercuribenzoate have been revealed by qualitative analysis. MDH2 is invariant. These findings indicate that the two forms are isozymes under independent genetic control. Other enzymes examined here exhibit only one isozyme, which shows genetic polymorphism in some strains. Using the variants and visible markers, the linkage groups of the structural loci of the enzymes have been identified: for some of them the genetic map position has been determined.