Evolution de la lutte contre la processionnaire du pin: vers l'utilisation de la phéromone de synthèse

Diffusion du document : INRA, Centre d'Avignon, Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex

Evolution de la lutte contre la processionnaire du pin: vers l'utilisation de la phéromone de synthèse

Diffusion du document : INRA, Centre d'Avignon, Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex

Population monitoring of the pine processionary moth (Lepidoptera: Thaumetopoeidae) with pheromone-baited traps

International audienceA series of tests were carried out to design pheromone-based monitoring of the pine processionary moth (PPM), Thaumetopoea pityocampa. In a dose–response field test the number of male captures increased significantly with the dosage of pityolure to a plateau around 10 mg. The activity of pheromone dispensers persisted for at least 11 weeks, enough to cover the entire flight period of T. pityocampa. In a comparison of several saturating and non-saturating trap designs, plate sticky traps always showed the highest trapping efficiency. Captures were significantly higher in regularly cleaned traps than in traps without cleaning, and at tree canopy height; however, the latter were positively correlated with captures from traps positioned at breast height. The relationship between the number of PPM males captured in pheromone traps and the density of winter nests was investigated in 14 stands of the maritime pine (Pinus maritima) using 10 traps baited with low doses of pityolure. Mean trap captures calculated from 3 traps schemes to 10 traps were significantly correlated with nest density, indicating that four plate sticky traps baited with 0.2 mg of pityolure would provide a cost-effective tool for monitoring population densities of PPM per hectare. The reliability of this design was tested in 33 pine stands of different age and tree species across a range of geographic regions (France, Italy, Portugal), both in the core and expansion areas of the pest. The results were remarkably consistent, showing significant and positive correlations between mean male captures per day and total number of winter nests per hectare irrespective of the regions. The correlations with the level of infestation in the following generation was also positive for all regions although less significant. Our findings suggest that pheromone-baited traps provide a suitable tool for monitoring of T.pityocampa population

Origin and taxonomic status of the Palearctic population of the stem borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae)

The major pest of maize in Mediterranean Europe, the stem borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae), has a fragmented distribution, north and south of the Sahara. The present study aimed: (1) to clarify the uncertain taxonomic status of the Palearctic and sub-Saharan populations which were first considered as different species and later on as subspecies (Sesamia nonagrioides nonagrioides and Sesamia nonagrioides botanephaga) and (2) to investigate the origin of the Palearctic population which extends from Spain to Iran, outside what is considered typical for this mainly tropical genus. We reconstructed the evolutionary history of both populations using one nuclear and two mitochondrial genes. The sub-Saharan taxon was fragmented in two isolated populations (West and East) whose mitochondrial genes were distant by 2.3%. The Palearctic population was included in the East African clade and its genes were close or identical to those of a population from Central Ethiopia, where the species was discovered for the first time. Similarly, in Africa, the alleles of the nuclear gene were distributed mainly in two West and East clades, whereas some Palearctic alleles belonged to the West clade. The Palearctic population originated therefore from East and West Africa and is the progeny of the cross between these two African populations. The main species concepts were in agreement, leading to the conclusion that the three populations are still conspecific. In the surveyed regions, the species therefore does not include two subspecies but three isolated populations. The Palearctic population suffered from severe bottlenecks that resulted in the fixation of one East African mitochondrial genome and the large reduction in its genetic diversity compared to the African populations. The data suggest that natural colonization of the Palearctic region was more plausible than human introduction. The allelic distribution of the Palearctic population was similar to that of species that survived the last glaciation. It is concluded that the African populations expanded during the last interglacial, crossed the Sahara and mixed in North Africa where fixation of the East mitochondrial genome occurred. The species then colonized Europe westward through only one eastern entrance. The coalescent-based estimate of the time to the ancestor of the Palearctic population was 108 000 years, which is consistent with this scenario

The 5 ' Region of the MSH2 gene involved in hereditary non-polyposis colorectal cancer contains a high density of recombinogenic sequences

MSH2 rearrangements are involved in approximately 10% of hereditary non,polyposis colorectal cancer (HNPCC) families, and in most of the rearrangements, exon I is deleted. We scanned by quantitative multiplex polymerase chain reaction (PCR) of short fluorescent fragments (QMPSF) 200 kb of genomic sequences upstream of the MSH2 transcription initiation site in 21 HNPCC families with exon I deletions. This QMPSF scan revealed 12 distinct 5' breakpoints located up to 200 kb upstream of the MSH2 transcription initiation site. Sequencing analysis of the rearranged allele in 17 families revealed that most of the deletions (15/17) resulted from homologous Alu-mediated recombination. QMPSF and sequencing analysis in these 21 families led us to detect the presence of 20 distinct 5' breakpoints. In 14 out of 15 Alu-mediated recombinations, we found, either within the identical region in which the recombination had probably occurred or in its vicinity, the 26,bp Alu core sequence containing the recombinogenic Chi-like motif. Compared to the equivalent regions of other human genes, the MSH2 upstream region was found to contain a high density of Alu repeats (30% within 228 kb and 43% within 50 kb), most of which belong to the old Alu S subfamilies. In conclusion, this study demonstrates the heterogeneity of the breakpoints within the MSH2 upstream region and reveals the remarkable density of recombinogenic Alu sequences in this region