Adaptation of the STICS intercrop model to simulate crop growth and N accumulation in pea–barley intercrops

Cereal–legume intercrops are gaining increasing interest in Europe. Modelling, by taking into account the complexity of species interactions, can be a very useful tool to study such systems and to test new strategies in various soil and climatic conditions. The present work describes the adaptation of an intercrop model for pea–barley intercrops through the extrapolation of the STICS sole crop model and its parameterisation from experimental data recorded on sole crops. Several improvements have been added to the existing crop model to allow an inversion of dominance in height between species during the crop cycle and a trophic link between crop growth rate and the potential for N₂ fixation. A 2-year dataset on pea and barley sole crops grown under non-limiting water conditions and with full crop protection was first used for calibration. The intercrop model was subsequently tested on experimental datasets of pea–barley intercrops grown under the same conditions as the sole crops. The intercrop experiments used to test the intercrop model differed in soil type, soil N supply and plant densities of each species.     

Beyond polarization: using Q methodology to explore stakeholders’ views on pesticide use,and related risks for agricultural workers,in Washington State’s tree fruit industry

Controversies in food and agriculture abound, with many portrayed as conflicts between polarized viewpoints. Framing such controversies as dichotomies, however, can at times obscure what might be a plurality of views and potential common ground on the subject. We used Q methodology to explore stakeholders’ views about pesticide safety, agricultural worker exposure, and human health concerns in the tree fruit industry of central Washington State. Using a purposive sample of English and Spanish-speaking agricultural workers, industry representatives, state agencies, educators, and advocates (n?=?41), participants sorted 45 statements on pesticide use and perceived human safety risks in the tree fruit industry in 2011. We used PQMethod 2.33 statistical software program to identify viewpoints, based on differences between how participants sorted the statements. The results revealed three distinct viewpoints among 38 sorters that explained 52 percent of the variance. The viewpoints included the: (1) skeptics (n?=?22) who expressed concern over the environmental and human health impacts of pesticide use; (2) acceptors (n?=?10) who acknowledged inherent risks for using pesticides but saw the risks as known, small and manageable; and (3) incrementalists (n?=?6) who prioritized opportunities to introduce human capital and technological improvements to increase agricultural worker safety. We then brought representatives with these different viewpoints together to analyze the results of the Q study, and to brainstorm mutually acceptable improvements to health and safety in tree fruit orchards. In describing and analyzing this case study, we argue that Q methodology can serve as one potentially effective tool for collaborative work, in this case facilitating a process of orchard safety improvements despite perceived stakeholder polarization.     

PCR-based detection of Pythium and Lagendium DNA in frozen and ethanol-fixed animal tissues

Abstract The purpose of this study was to evaluate the application of previously described Pythium insidiosum‐ and Lagenidium‐specific nested PCR assays to the detection of oomycete DNA in animal tissues. DNA was extracted from 15 frozen and 10 ethanol‐fixed tissues obtained from six animals with pythiosis, five animals with lagenidiosis, one animal with nonoomycotic skin disease and two animals without skin disease. First‐round PCR, which utilized universal fungal primers ITS1 and ITS2P, amplified a single product of the expected size for each of the P. insidiosum‐ and Lagenidium‐infected tissues, but not for tissues obtained from animals without fungal disease. Second‐round PCR using the P. insidiosum‐specific primers PI1 and PI2 produced a single 105‐bp product for the P. insidiosum‐infected tissues, but not for any of the other tissues. Second‐round PCR using the Lagenidium‐specific primers LAG1 and LAG2 produced a single 76‐bp product for the Lagenidium‐infected tissues, but not for any of the other tissues.     

A limited role for SsrA/B in persistent Salmonella Typhimurium infections in pigs

Virulence genes regulated by the SsrA/B system are indispensable for systemic disease in BALB/c mice. The role of this regulating system in the pathogenesis of Salmonella Typhimurium infections in pigs is not documented. In the present study, the interactions of Salmonella Typhimurium and an ssrA/B mutant were compared in vitro and in vivo. The ssrA/B mutant strain displayed decreased Salmonella Pathogenicity Island 2 (SPI-2) expression levels, showed a replication defect in mouse macrophages and was attenuated in a mouse model after oral inoculation. Using real time qRT-PCR and a porcine ileal loop model, it was shown that the ssrA/B mutant strain was not significantly attenuated in overall virulence and SPI-1 expression in specific. Flowcytometric analysis demonstrated that the ssrA/B mutant strain was defective in intracellular replication in porcine macrophages. After oral inoculation of piglets with the wild type strain or the ssrA/B mutant strain, the animals of both groups excreted Salmonella and were colonized by Salmonella to the same extent. In an intravenous mixed infection model, the ssrA/B mutant strain was defective in the colonization of several internal organs. These results suggest that the ssrA/B gene of Salmonella Typhimurium plays a limited role in the persistent intestinal colonization of pigs.     

On the origin of leprosy

Leprosy, a chronic human disease with potentially debilitating neurological consequences, results from infection with Mycobacterium leprae. This unculturable pathogen has undergone extensive reductive evolution, with half of its genome now occupied by pseudogenes. Using comparative genomics, we demonstrated that all extant cases of leprosy are attributable to a single clone whose dissemination worldwide can be retraced from analysis of very rare single-nucleotide polymorphisms. The disease seems to have originated in Eastern Africa or the Near East and spread with successive human migrations. Europeans or North Africans introduced leprosy into West Africa and the Americas within the past 500 years.     

Nanoparticle superlattice engineering with DNA

A current limitation in nanoparticle superlattice engineering is that the identities of the particles being assembled often determine the structures that can be synthesized. Therefore, specific crystallographic symmetries or lattice parameters can only be achieved using specific nanoparticles as building blocks (and vice versa). We present six design rules that can be used to deliberately prepare nine distinct colloidal crystal structures, with control over lattice parameters on the 25- to 150-nanometer length scale. These design rules outline a strategy to independently adjust each of the relevant crystallographic parameters, including particle size (5 to 60 nanometers), periodicity, and interparticle distance. As such, this work represents an advance in synthesizing tailorable macroscale architectures comprising nanoscale materials in a predictable fashion.     

Selection for tetracycline-resistant Chlamydia suis in treated pigs

The aim of this study was to investigate Chlamydia suis in a pig farm with an outbreak of conjunctivitis and diarrhea. Eye swabs and pooled fecal samples were investigated for the presence of C. suis by real-time PCR and ArrayTube microarray. Samples positive for C. suis by ArrayTube microarray assay were further tested for the presence of the tet(C) resistance gene by PCR. In the first examination, C. suis was identified in 12 six-week-old pigs showing conjunctivitis. Of these, the tet(C) gene-coding region was amplified in one pooled fecal sample and one eye swab, respectively. After oral treatment with tetracycline, clinical symptoms disappeared. Subsequently, all eye swabs investigated from 10 healthy pigs were positive for C. suis and the tet(C) gene-coding region. The present study reports rapid selection for tetracycline-resistant C. suis after antibiotic treatment.     

Experimental infection of crickets (Gryllus bimaculatus) with an invertebrate iridovirus isolated from a high-casqued chameleon (Chamaeleo hoehnelii).

Invertebrate iridoviruses (IIV) have been a regular problem for insect breeders. They have also recently been isolated from various lizard species. An iridovirus isolated from several tissues of a high-casqued chameleon (Chamaeleo hoehnelii) was identified as an IIV on the basis of electron microscopy (EM), sequencing of a portion of the major capsid protein (MCP) gene, and restriction endonuclease analysis of viral DNA. The pathogenicity of this isolate for crickets of the species Gryllus bimaculatus was tested by using 3 experimental infection studies. The mortality rates in the infected crickets ranged between 20% and 35%. The fat bodies of the crickets were examined on cell culture, with a nested PCR targeting the MCP gene, histologically, with in situ hybridization and by EM. Nested PCR was the most sensitive method for detecting IIV in the fat-body samples. Virus was re-isolated from several fat-body samples. In some fat bodies of infected crickets, massive arrays of viruses could be detected by EM. These findings support the hypothesis that IIV from insects are able to infect reptiles.