Role of transporters in paraquat resistance of horseweed Conyza canadensis (L.) Cronq.

Paraquat (Pq) inducible transporters are presumed to play a role in the resistance mechanism of horseweed and to function by carrying paraquat to a metabolically inactive compartment. The uptake and intracellular localisation of paraquat, the effect of transporter inhibitors on resistance, and paraquat-induced gene expression were studied to obtain a better understanding of the mechanism of resistance. Investigations proved that paraquat entered the cells of both resistant and susceptible biotypes, approached the maximum within the first hour in chloroplasts, and then declined in all organelle fractions. In the resistant biotype paraquat was located in the vacuoles a day after treatment. Selective transporter inhibitors blocked the sequestration of paraquat, suggesting the participation of not directly energized transporters. Four EST fragments were identified that were expressed in response to paraquat. Two of them are thought to play a role in the general stress response (Ferr2, Myb). The others exhibit a similarity to transporters (EmrE, CAT) and could conceivably be involved in the intracellular transport of paraquat and the mechanism of resistance.     

AFLPs in leek ( Allium porrum) are not inherited in large linkage blocks

Genetic linkages of 1:1 segregating amplified fragment length polymorphism (AFLP^TM) markers in leek (2n=4x=32) were studied with the aim of detecting block inheritance resulting from strong suppression of crossing over in chromosomal arms. The study comprised 97 markers in 70 plants originating from a cross between two highly heterozygous parents. At LOD≥3, 52 markers were linked in 23 linkage groups, spanning 405 of an expected 6400 cM. Cytogenetic data in previous studies indicated that recombination may be suppressed in two-thirds of the leek genome, supposedly leading to large linkage blocks of markers. In the present study, however, comparison of AFLP linkages with simulations indicates that the linkage blocks are much smaller, comprising no more than one-third of the leek genome. This revised version was published online in August 2006 with corrections to the Cover Date.     

Popular music in a transnational world: the construction of local identities in Singapore

As an area of geographical inquiry, popular music has not been explored to any large extent. Where writings exist, they have been somewhat divorced from recent theoretical and methodological questions that have rejuvenated social and cultural geography. In this paper, I focus on one arena which geographers can develop in their analysis of popular music, namely, the exploration of local influences and global forces in the production of music. In so doing, I wish to explore how local resources intersect with global ones in a process of transculturation. Using the example of English songs by one particular songwriter and artiste whose works are part of the popular music industry mainstream, and that of Mandarin songs of the genre xinyao, I will show that, despite increasing globalising forces, music is still an expression of local/national influences. Indeed, I will argue that globalisation intensifies localisation.     

Attraction to prey and prey-associated odours by the predatory mite Hypoaspis aculeifer in a soil experimental system

In terms of food searching and trophic interactions among soil organisms volatile signalling plays a crucial role. Still, volatile-based foraging decisions are poorly understood, especially as the dispersal and perception of cues is more restricted within the soil pore space than in simple laboratory approaches where volatiles disperse freely in the air. Focusing on the tritrophic interaction between the soil fungus Trichoderma viride, the fungivorous collembolan Folsomia candida and the predatory mite Hypoaspis aculeifer, we tested the effect of prey and prey-associated volatile signals on the food choice decision of the predatory mite in a laboratory experiment under soil conditions as well as the possible occurrence and relevance of grazing-induced indirect defence signals. The mites showed a clear preference for ungrazed and grazed fungal mycelium. However, we found no evidence of induced indirect defence as ungrazed mycelium was preferred to grazed fungus.     

Detection of tobacco rattle virus in different parts of tulip by ELISA and cDNA hybridisation assays

Different parts of tulips cv. Apeldoorn were assayed for the presence of tobacco rattle virus (TRV) by means of ELISA, cDNA hybridisation and immuno-electron microscopy. Assays were periodically performed during the growing season and upon storage of the bulbs, During the growing season in the field the relative TRV concentrations detected by ELISA and cDNA were highest mainly in the basal stem-parts and basal leaf-parts, respectively. When, during storage, infected bulbs were divided into a number of sections, TRV could be detected only in some of the sections, irrespective of the test used. However, nearly all sprouts of infected bulbs, stored at 5°C for 7 months, appeared to contain detectable amounts of TRV upon testing with ELISA and cDNA. Thus, testing of sprouts may offer a possibility to develop a routine test for TRV in tulip bulbs in due course.Samenvatting Verschillende delen van tulp cv. Apeldoorn werden getoetst op de aanwezigheid van tabaksratelvirus (TRV) met behulp van ELISA, cDNA-hybridisatie en immuno-elektronemicroscopie. Tijdens het groeiseizoen en de bewaring van de bollen werden regelmatig toetsingen uitgevoerd. Gedurende het groeiseizoen op het veld werden de relatief hoogste TRV concentraties voornamelijk gevonden in het basale deel van de stengel en het okselgedeelte van het blad met respectievelijk ELISA en cDNA-hybridisatie. TRV bleek gelokaliseerd aanwezig te zijn in een of meer stukjes van een gedeelde bol, onafhankelijk van de gebruikte toetsmethode. Bijna alle spruiten van geïnfecteerde bollen die gedurende 7 maanden bij 5°C bewaard waren, bleken bij het toetsen met behulp van ELISA en cDNA aantoonbare hoeveelheden van TRV te bevatten. Het toetsen van spruiten biedt de mogelijkheid te zijner tijd een routinetoets voor TRV in tulpebollen te ontwikkelen.