The taxonomic status of the tephritid pest Anastrepha fraterculus (Wied.) is a controversial subject, mainly because of misinterpretation of the observed genetic variation. In this work, the different karyotypes and DNA polymorphism of a geographically defined population from Northeastern Argentina were studied, using derived stocks maintained in the laboratory during 25 generations. The karyotypes were analyzed using C-banding and N-banding techniques, while DNA analysis was performed through the DNA polymerase chain reaction (PCR). The variants isolated from both the wild Montecarlo population and the derived laboratory stocks were fully compatible and are present in other wild populations from South Brazil (lat 31 degrees 30' S) to Mid-Argentina (lat 34 degrees 30' S). Single-pair crosses among stocks carrying different chromosomal variants demonstrated the absence of isolation barriers. The polymorphic fragments isolated by RAPDs/PCR showed polymorphisms among stocks whereas the analysis of rDNA ITS1 exhibit a unique ITS1 length. Our results seem to indicate that all the examined variants belong to a single species with extended polymorphism and therefore do not support the hypothesis that the extended chromosomal polymorphism in A. fraterculus implies the existence of a complex of cryptic species.
A random amplified polymorphic DNA polymerase chain reaction method using 10-base long commercial random primers was used to identify polymorphisms in Argentine populations of 2 fruit fly pests. A fast and reliable discrimination between Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and Anastrepha fraterculus (Wiedemann) immature or mature stages was obtained using as few as 1 insect per assay. The population of origin of immature individuals can be identified unambiguously using 2 primers.
BackgroundThe Mediterranean fruit fly Ceratitis Capitata (DIPTERA: Tephritidae) is a major agricultural pest in Argentina. One main cause for the success of non-contaminant control programs based on genetic strategies is compatibility between natural and laboratory germplasms.A comprehensive characterization of the fruit fly based on genetic studies and compatibility analysis was undertaken on two founder populations from the provinces of Buenos Aires and Mendoza, used in pioneering sterile male technique control programmes in our country. The locations are 1,000 km apart from each other.Methodology/Principal FindingsWe compared the genetic composition of both populations based on cytological, physiological and morphological characterization. Compatibility studies were performed in order to determine the presence of isolation barriers. Results indicate that the Buenos Aires germplasm described previously is partially different from that of the Mendoza population. Both laboratory colonies are a reservoir of mutational and cytological polymorphisms. Some sexual chromosome variants such as the XL and the YL resulting from attachment of a B-chromosome to the X-chromosome or Y-chromosome behave as a lethal sex-linked factor. Our results also show incompatibility between both germplasms and pre-zygotic isolation barriers between them. Our evidence is consistent with the fact that polymorphisms are responsible for the lack of compatibility.ConclusionsThe genetic control mechanism should be directly produced in the germplasm of the target population in order to favour mating conditions. This is an additional requirement for the biological as well as economic success of control programs based on genetic strategies such as the sterile insect technique. The analysis of representative samples also revealed natural auto-control mechanisms which could be used in modifying pest population dynamics.
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