Biochemical characterization of sibling species in Tunisian Mayetiola (Diptera : Cecidomyiidae)

In Morocco, two sympatric species of Mayetiola (destructor and hordei) have been identified on the basis of microscopic characters. Barley is almost e xclusively colonized by M. hordei and presents distinct stem swellings (gal ls), whereas wheat is almost exclusively colonized by M. destructor and has no gall. In Tunisia, previous studies have shown that Mayetiola infestatio ns of wheat or barley never produce galls in the northern region, whereas g alls are frequent on barley in the center and the rule in the south. In the present study, we have investigated the electrophoretic polymorphism at fo ur loci of Mayetiola collected on field plants presenting or lacking galls from northern and central Tunisia. We showed that, in central Tunisia, two reproductively isolated groups were present in all samples from wheat, barl ey and oat whether these plants carried gall or not, In contrast, only one of these groups was found in samples from wheat and barley lacking galls fr om the north. On the basis of a comparison with Moroccan strains of the two species, these groups were identified as M. hordei and M. destructor which can easily be characterized by diagnostic alleles at two loci, Pgi and Mdh 2. (C) 2000 Elsevier Science Ltd. All rights reserved.