Genetic diversity of Mayetiola destructor and Mayetiola hordei (Diptera: Cecidomyiidae) by inter-simple sequence repeats (ISSRs)

Inter-simple sequence repeats (ISSR) polymorphism was used to reveal genetic variability and phylogenetic relationships within and between three haplotypes of Mayetiola species. A set of 14 ISSR primers were screened representing di-, tri, tetra and penta-nucleotide repeats out of which 10 generated scorable bands and three were able to distinguish one of three haplotypes. The consensus tree constructed using binary data from banding patterns generated by ISSR-PCR clustered the two Mayetiola species according to their mitochondrial haplotype. Moreover, genetic diversity estimated by the coefficient of variation indicates a high intra and inter-haplotypes polymorphism. Our results indicate that ISSR can be useful as DNA-based molecular markers for studying genetic diversity and phylogenetic relationships of Mayetiola haplotypes.African Journal of Biotechnology Vol. 4 (7), pp. 601-606, 200

Structure génétique des cécidomyies des céréales en Tunisie

Genetic structure of Hessian flies in Tunisia. The genetic structure of M. destructor and M. hordei was investigated by sampling 21 fields of cereals in 14 localities of central and southern Tunisia. As previously shown, there was no strict association between the cereal species (wheat, barley and oat) and the Mayetiola species. M. destructor males displayed no heterozygosity at the Pgm3 locus, indicating that they were hemizygous as is the PGM locus in North America. In M. hordei, heterozygous males were observed at all loci, but strong heterozygote deficits were found at two loci (Mdh2 et Hk). Since no such deficit was observed in females, the population structure of M. hordei was studied only in females. Although heterozygosity was two fold higher in M. hordei than in M. destructor, the two species were similar for other genetic characteristics, including a low (Fst < 0.05) but significant (P < 0.05) genetic differentiation, no isolation by distance, and similar rates of gene flow (5.7 ≤ Nm ≤ 9.6). These results are discussed in relation to their consequences in the event of controlling Tunisian Hessian flies using wheat cultivars that are resistant to a M. destructor biotype

Razlučivanje dviju vrsta mušica šiškarica (Diptera: Cecidomyiidae) otkrivanjem razlika u genima za mitohondrijsku DNA

Mayetiola is an important pest of cereal in Tunisia. Two species were identified using isoenzymatic markers. To develop a DNA diagnostic tool, we assessed mitochondrial DNA study based on Restriction Fragment Length Polymorphism in Polymerase Chain Reaction Amplified Fragments (PCR -RFLP). Specific primers were used to amplify the cytochrome b and a 3’ terminal region of the 12S mt rDNA genes. Results showed that Sau3A restriction patterns can distinguish between the two morphologically similar species. Thus PCR-RFLP is a useful tool for identifying morphologically simiIar species of Mayetiola in large-scale pest identification.Mayetiola je važan nametnik na žitaricama u Tunisu, a dvije vrste bile su određene upotrebom izoenzimskih biljega. Kako bismo razvili dijagnostički alat zasnovan na upotrebi molekule DNA, pristupili smo proučavanju mitohondrijske DNA metodom praćenja polimorfizma duljine restrikcijskih fragmenata nakon lančane reakcije polimerazom (PCR-RFLP). Kako bi se umnožio gen za citokrom b i 3’ terminalno područje 12S mt rDNA bile su upotrijebljene specifične klice. Rezultati pokazuju kako se uzorak razgradnje dobiven restrikcijskim enzimom Sau3A razlikuje između dviju morfološki sličnih vrsta. Tako je ustanovljeno kako je PCR-RFLP metoda korisna za razlučivanje morfološki sličnih vrsta Mayetiola prilikom identifikacije ovih štetnika u velikom uzorku

Usporedba dviju skupina vrsta Mayetiola u različitim geografskim uvjetima: utjecaj varijacija biljke domaćina.

In Tunisia, two species of Mayetiola (M. destructor and M. hordei) have been identified on the basis of diagnostic alleles and PCR-RFLP of the cytochrome b gene. They are the major pests of wheat and barley responsible for serious crop losses. As these two species show feeding preferences between cereals, knowledge of the population dynamics of this phytophagous insect is needed in order to survey ecology and evolution of host parasite interaction. In this study, the PCR-RFLP technique based on the cytochrome b gene was used to identify the two species of Mayetiola and to investigate the relationships with their hosts. The comparison of Mayetiola assemblages on barley in different regions in Tunisia, showed a continual geographical gradient variation in species compositions and dominance order. However, on wheat there is a homogenous distribution. Thus, monitoring of pest must take into account our finding that population assemblage differs from host types and geographical location.U Tunisu su utvrdene dvije vrste roda Mayetiola (M. destructor i M. hordei) koristeći diagnostičke allele i PCR-RFLP citokroma b gena. Ove su vrste važni štetnici pienice i ječma te čine velike štete. Kako pokazuju preferenciju pri ishrani ovih žitarica potrebno je poznavati njihovu dinamiku populacije kako bi se mogle pratiti interakcije izmedu štetnika i domaćina. U ovim istraživanjima korištene su PCR- RFLP tehnike temeljene na citokromu b gena za identifikaciju obih vrsta i utvrđivanje odnosa prema domaćinu. Usporedba skupina vrsta roda Mayetiola na ječmu u različitim dijelovima Tunisa pokazala je kontinuirani geografski gradijent u sastavu vrste i redu dominantnosti. Medutim, na pšenici je distribucija homogena. Stoga se kod monitoringa štetnika moraju uzeti u obzir ovi nalazi prema kojima populacija ovisi o vrsti domaćina i geografskog lokaliteta

HESSIAN FLY, Mayetiola destructor (Say), POPULATIONS IN THE NORTH OF TUNISIA: VIRULENCE, YIELD LOSS ASSESSMENT AND PHENOLOGICAL DATA

Hessian fly, Mayetiola destructor (Say), is a destructive pest of wheat worldwide and an endemic pest in Tunisia. Two natural populations of this insect from the North of Tunisia were evaluated, in the field, for their virulence, based on response developed by bread wheat ( Triticum aestivum L.) cultivars carrying H3, H5, H6, H7H8, H11, H13 and H16 resistance genes. H11, H13 and H16 showed a high effectiveness against both populations; therefore, their implication in Hessian fly breeding programs would be of interest. The level of infestation, as well as the yield loss, was assessed, based on the percentage of infested plants and variation in growth parameters due to infestation. The percentage of infested plants, over a 2-yr period in Mateur, averaged 18.82% for durum wheat ( Triticum turgidum L. subsp. durum (Desf.) Husn.) and 32.50% for bread wheat. For the improved durum wheat cv. Karim used as reference, the plant height, number of internodes, number of productive tillers per plant, and 100-seed weight were negatively affected by infestation, while the number of tillers per plant was positively affected. Aiming to update information about the annual number of the fly generations occurring on wheat, we surveyed infestation in Jédéida. At least three Hessian fly generations were detected on bread wheat and durum wheat. Continued regular surveying of Hessian fly populations in terms of virulence, impact on yield and annual generations is required for optimal deployment of resistance genes and integrated management of Hessian fly across all wheat production areas

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 exclusively colonized by M. hordei and presents distinct stem swellings (galls), whereas wheat is almost exclusively colonized by M. destructor and has no gall. In Tunisia, previous studies have shown that Mayetiola infestations of wheat or barley never produce galls in the northern region, whereas galls are frequent on barley in the center and the rule in the south. In the present study, we have investigated the electrophoretic polymorphism at four 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, barley 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 from 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 Mdh2