Linkage map construction involving a reciprocal translocation

This paper is concerned with a novel statistical–genetic approach for the construction of linkage maps in populations obtained from reciprocal translocation heterozygotes of barley (Hordeum vulgare L.). Using standard linkage analysis, translocations usually lead to ‘pseudo-linkage’: the mixing up of markers from the chromosomes involved in the translocation into a single linkage group. Close to the translocation breakpoints recombination is severely suppressed and, as a consequence, ordering markers in those regions is not feasible. The novel strategy presented in this paper is based on (1) disentangling the “pseudo-linkage” using principal coordinate analysis, (2) separating individuals into translocated types and normal types and (3) separating markers into those close to and those more distant from the translocation breakpoints. The methods make use of a consensus map of the species involved. The final product consists of integrated linkage maps of the distal parts of the chromosomes involved in the translocation

Absence of knockdown resistance suggests metabolic resistance in the main malaria vectors of the Mekong region

<p>Abstract</p> <p>Background</p> <p>As insecticide resistance may jeopardize the successful malaria control programmes in the Mekong region, a large investigation was previously conducted in the Mekong countries to assess the susceptibility of the main malaria vectors against DDT and pyrethroid insecticides. It showed that the main vector, <it>Anopheles epiroticus</it>, was highly pyrethroid-resistant in the Mekong delta, whereas <it>Anopheles minimus sensu lato </it>was pyrethroid-resistant in northern Vietnam. <it>Anopheles dirus sensu stricto </it>showed possible resistance to type II pyrethroids in central Vietnam. <it>Anopheles subpictus </it>was DDT- and pyrethroid-resistant in the Mekong Delta. The present study intends to explore the resistance mechanisms involved.</p> <p>Methods</p> <p>By use of molecular assays and biochemical assays the presence of the two major insecticide resistance mechanisms, knockdown and metabolic resistance, were assessed in the main malaria vectors of the Mekong region.</p> <p>Results</p> <p>Two FRET/MCA assays and one PCR-RFLP were developed to screen a large number of <it>Anopheles </it>populations from the Mekong region for the presence of knockdown resistance (<it>kdr</it>), but no <it>kdr </it>mutation was observed in any of the study species. Biochemical assays suggest an esterase mediated pyrethroid detoxification in <it>An. epiroticus </it>and <it>An. subpictus </it>of the Mekong delta. The DDT resistance in <it>An. subpictus </it>might be conferred to a high GST activity. The pyrethroid resistance in <it>An. minimus s.l</it>. is possibly associated with increased detoxification by esterases and P450 monooxygenases.</p> <p>Conclusion</p> <p>As different metabolic enzyme systems might be responsible for the pyrethroid and DDT resistance in the main vectors, each species may have a different response to alternative insecticides, which might complicate the malaria vector control in the Mekong region.</p

The effect of the amimal-drawn mould boars plough without the coulter on traction in Ghana

No Abstract. Journal of the Ghana Science Association Vol. 2 (2) 1999: pp.32-3

Land preparation and moisture conservation with rice cultivation in the Northern region of Ghana

No Abstract. Journal of the Ghana Science Association Vol. 1 (1) 1999: pp.41-4

The use of solar dryer to control insect infestation in stored grains in Ghana

A study was carried out to assess the effectiveness of a simple solar dryer, built from local materials, to control cowpea bruchids, Callosobruchus maculatus (Fabricuis) and maize weevils, Sitophilus zeamais (Motsch.) in infested cowpea and maize. The effect of the heat generated in the solar dryer on the mortality of the insects, viability of the cowpea and maize seeds and the emergence of F1 progeny of C. maculatus and S.zeamais were the parameters assessed. The result obtained showed the reliability of the simple, low cost solar dryer in controlling the insects to an appreciable level. Complete (100%) mortality was obtained when theinfested cowpea and maize were placed in the solar dryers, for 60 minutes and 120 minutes, respectively. The highest mean percent seed viability of the infested cowpea was 66.4% after being exposed for 120 minutes inthe solar dryer and least viability was 48.5%. However, the mean percent seed viability of the infested maize decreased from 85% after 30 minutes of exposure in the solar dryer to 59.0% after 4 hours. The test indicatedthat exposure of the seed to the heat in the solar dryer reduced viability. The control for both cases gave higher percentage seed viability 73% and 86% for cowpea and maize, respectively. The period of exposure of theinfested grains in the solar dryer for one hour or more also effectively reduced the number of F1 progeny that emerged from the stored grains. The result for solar-treated seeds was only effective as post-harvest reduction in weevil injury and may not be viable for planting due to loss in germination.Keywords: mortality, viability, F1 progeny, C. maculatus, S. zeamais

Genetic characterization of a reciprocal translocation present in a widely grown barley variety

Artificially induced translocation stocks have been used to physically map the barley genome; however, natural translocations are extremely uncommon in cultivated genotypes. Albacete is a barley variety widely grown in recent decades in Spain and carrying a reciprocal translocation which obviously does not affect its agronomical fitness. This translocation has been characterized by a combination of cytological and molecular genetic approaches. Firstly, recombination frequencies between markers on chromosomes 1H and 3H were estimated to determine the boundaries of the reciprocal interchange. Secondly, 1H-3H wheat barley telosome addition lines were used to assign selected markers to chromosome arms. Thirdly, fluorescence in situ hybridization (FISH) with rDNA probes (5S and 18S-5.8S-26S) and microsatellite probes [(ACT)5, (AAG)5 and (CAG)5] was used to determine the locations of the translocation breakpoints more precisely. Fourthly, fine-mapping of the regions around the translocation breakpoints was used to increase the marker density for comparative genomics. The results obtained in this study indicate that the translocation is quite large with breakpoints located on the long arms of chromosomes 1H and 3H, between the pericentromeric (AAG)5 bands and above the (ACT)5 interstitial distal bands, resulting in the reciprocal translocation 1HS.1HL-3HL and 3HS.3HL-1HL. The gene content around the translocation breakpoints could be inferred from syntenic relationships observed among different species from the grass family Poaceae (rice, Sorghum and Brachypodium) and was estimated at approximately 1,100 and 710 gene models for 1H and 3H, respectively. Duplicated segments between chromosomes Os01 and Os05 in rice derived from ancestral duplications within the grass family overlap with the translocation breakpoints on chromosomes 1H and 3H in the barley variety Albacete