Life history traits and trade-offs between two species of the ascochyta blight disease complex of pea

Plant disease complexes are a playground to investigate coinfections in natural or cultivated systems. Pathogens of such complexes may affect each other through direct and/or indirect interactions and lead to changes in virulence or aggressiveness, offspring production, and transmission. As coinfections by sympatric host-pathogens can strongly influence pathogen dynamics and their evolutionary trajectories, new insights into the mechanisms of their coexistence is thus of critical importance. In order to characterize differences in ecological niches liable to explain species coexistence on the same host, the inter- and intraspecific diversity of the life history traits in natural collections of the two main pathogens (Peyronellaea (formerly Didymella) pinodes [Dp] and Phoma medicaginis var. pinodella [Pmp]) of the ascochyta blight disease complex of pea was evaluated under controlled conditions. Dp strains developed 1.3 times faster and produced longer, mainly bicellular spores and in lower amounts (3.7 times less) than Pmp strains. Pmp strains were separated into two groups, one producing more pycnidiospores, mainly bicellular, with less resources, and the other with mainly unicellular ones. These three groups can be interpreted as three distinct life history strategies: pioneer colonizer (Dp), scavenger (large-spored Pmp), and intermediate (small-spored Pmp), allowing differentiation in access to and use of resources. While this experimental work provides new insight into coexistence of two species of the ascochyta blight disease complex of pea, it also raises the question of the benefit of having two distinct life history strategies for one species (Pmp).     

Molecular diversity of barley yellow dwarf virus-PAV from China and the Czech Republic

Wheat yellow dwarf disease (BYD), caused by different species of barley/cereal yellow dwarf viruses (B/CYDVs), is one of the most serious cereal diseases in China and the Czech Republic. Because genetic diversity of the virus directly influences disease epidemiology, the molecular diversity and population structure of 24 Chinese isolates and 16 the Czech Republic isolates of BYDV-PAV from different regions in two countries were analyzed by sequencing their coat protein (CP) and readthrough protein (RTP) domain (RTD) genes and comparing the sequences with six CP and 16 RTP sequences of BYDV-PAV isolates from the NCBI database based on nucleotide identity position, phylogenetic analysis and nucleotide diversity. Nucleotide identities between the Chinese and the Czech Republic isolates for the CP were 76.6–99.4%, 73.9–89.1% for RTD (ORF5), respectively. The Chinese and the other country isolates showed 74.7–99.2% nucleotide identity for RTP (ORF3+ORF5). Phylogenetic analysis of CP sequences showed that 20 Chinese isolates clustered in the same clade, but the other four Chinese isolates clustered in another clade with the isolates from the Czech Republic and other counties. The population of BYDV-PAV in China had greater nucleotide variability and was more divergent than that in the Czech Republic. Geographical and ecological factors but not hosts might contribute to the population differences in the two countries.     

Screening events to reduce farmers' hazardous exposures

Dairy farmers may be exposed to high levels of noise and dust. Protections against these hazards exist, but many farmers do not use them. An intervention consisting of hearing and respiratory screenings combined with personalized education was implemented. This study evaluates the impact of this intervention on farmers' self-reported use of personal protective equipment (PPE) and implementation of noise and dust abatement. Participants were screened as to noise (n=209) or dust (n=392) hazards and use of PPE. Following this, they were counseled on PPE use, and identification and reduction of noise or dust hazards. Counselors sought a pledge from the farmers to eliminate hazards and increase PPE use. Farmers were subsequently surveyed and asked whether they had implemented the changes. At baseline, 70% (146/209) of farmers exposed to high levels of noise reported poor use ("sometimes", "rarely", or "never") of hearing protection. Results indicated that two months after intervention, 25.2% (28/111) of these subjects had successfully improved their PPE use. At baseline, 79% (311/392) offarmers reported poor use of respiratory protection, with 27.3% (41/150) showing improvement in PPE use within the same time. Strategies to reduce noise hazards were identified by 92.8% (194/209) of hearing screening attendees; 13.2% (18/136) successfully reduced or removed exposure. These values for dust screening attendees were 98.2% (385/392) and 30.7% (54/176), respectively. Use of this intervention appears to be an effective method for increasing PPE use on the farm. However, it is not effective for reducing noise hazards.     

Rollover protection on New York tractors and farmers' readiness for change

Tractor overturns contribute significantly to fatalities in New York State agriculture. On-site inspections a decade ago indicated that approximately 60% of tractors were without effective rollover protection. Our objectives were: to describe the current prevalence and distribution of rollover protective structures (ROPS) on New York farm tractors, to identify characteristics associated with the absence of ROPS, to explore segmenting the New York farm community on readiness for ROPS retrofitting, and to identify demographic characteristics that might assist in this segmenting. A random selection of 644 livestock, dairy, fruit, cash crop, vegetable, and organic farms were contacted for a telephone survey. Of 562 farms (87%) participating, 102 (18.1%) had all tractors equipped with ROPS and 138 (24.6%) had none. A disproportionate number of livestock, cash crop, and organic operations had no ROPS. Rates of ROPS-equipped tractors correlated directly with farm size and annual hours of tractor operation. Older farmers had a lower proportion of ROPS tractors. The presence of a child operator did not affect the proportion of ROPS tractors. After weighting the sample, the total number of non-ROPS tractors in New York is estimated at more than 80,000. In addition to providing key farm demographics, the survey enabled placement of farmers on a "stage of change" continuum related to readiness for retrofitting. Three-quarters of New York farmers are in the "precontemplation" stage of change relative to ROPS retrofitting, and this varies little by size of operation, age of farmer, or the presence of child tractor operators. Stage of change may relate to hours of tractor operation (p = 0.05) and does relate to commodity (p = 0.003) due primarily to the higher proportion of crop farmers in the earliest stage of change. The goal of retrofitting all New York farm tractors with ROPS appears nearly as daunting as it did a decade ago.     

A major genome region underlying artemisinin resistance in malaria

Evolving resistance to artemisinin-based compounds threatens to derail attempts to control malaria. Resistance has been confirmed in western Cambodia and has recently emerged in western Thailand, but is absent from neighboring Laos. Artemisinin resistance results in reduced parasite clearance rates (CRs) after treatment. We used a two-phase strategy to identify genome region(s) underlying this ongoing selective event. Geographical differentiation and haplotype structure at 6969 polymorphic single-nucleotide polymorphisms (SNPs) in 91 parasites from Cambodia, Thailand, and Laos identified 33 genome regions under strong selection. We screened SNPs and microsatellites within these regions in 715 parasites from Thailand, identifying a selective sweep on chromosome 13 that shows strong association (P = 10(-6) to 10(-12)) with slow CRs, illustrating the efficacy of targeted association for identifying the genetic basis of adaptive traits.     

Age‐Dependent Morphology of NADPH Diaphorase‐Positive Amacrine Cells in the Mouse Retina

NADPH diaphorase‐positive amacrine cells (NAC) were studied in retinal whole mount preparation of mice, ranging from 1 day to 30 months of age. Following a peak in number and size during early development at postnatal day 14, their number and distribution remained well preserved up to senescence. Functional considerations include immunological, vascular and neuro‐modulating aspects.     

Effects of sialidase knockout and complementation on virulence of Mycoplasma gallisepticum

Reannotation of the pathogenic Mycoplasma gallisepticum strain R(low) genome identified the hypothetical gene MGA_0329 as a homolog of the sialidase gene MS53_0199 of Mycoplasma synoviae strain MS53. Potent sialidase activity was subsequently quantitated in several M. gallisepticum strains. Because sialidase activity levels correlate significantly with differing M. synoviae strain virulence, we hypothesized this enzyme may also influence the virulence of M. gallisepticum. MGA_0329 was disrupted in strain R(low) to create mutants 6, 358 and P1C5, which resulted in the loss of sialidase activity in all three mutants. Chickens infected with the knockout mutants had significantly less severe (P<0.05) tracheal lesions and tracheal mucosal thickening than chickens infected with equal doses of strain R(low). Significantly fewer (P<0.05) CCU especially of strains 6 and P1C5 were recovered at necropsy. Mini-Tn4001tet plasmid pTF20 carrying a wild-type copy of MGA_0329 with its native promoter was used to complement the genetic lesion in strain P1C5. Three clones derived from P1C5, each having one copy of MGA_0329 stably transposed into a different site in its genome, expressed sialidase restored to wild-type activity levels (1.58×10(-8)U/CFU). Complementation of P1C5 with MGA_0329 did not restore it to wild-type levels of virulence, indicating that the contribution of sialidase to M. gallisepticum virulence is not straightforward.     

Effects of a mock ultrasonographic procedure on cortisol concentrations during low-dose dexamethasone suppression testing in clinically normal adult dogs

OBJECTIVE: To determine whether the stress of an ultrasonographic procedure would interfere with the suppressive effect of dexamethasone during a low-dose dexamethasone suppression test (LDDST) in healthy dogs. ANIMALS: 6 clinically normal adult dogs. PROCEDURE: In phase 1, an LDDST was performed 5 times at weekly intervals in each dog. Serum samples were obtained 0, 2, 4, 6, and 8 hours after dexamethasone injection. A mock 20-minute abdominal ultrasonographic examination was performed on all dogs at each time point during the LDDST on weeks 2 through 5. In phase 2, serum cortisol concentrations were measured before and immediately after a 20-minute mock abdominal ultrasonographic examination, as described for phase 1. RESULTS: We did not detect significant differences after dexamethasone injection when comparing median cortisol concentrations for weeks 2 to 5 (mock ultrasonographic procedure) with median concentration for week 1 (no mock ultrasonographic procedure). For 5 of the 6 dogs, cortisol concentrations after dexamethasone injection decreased to < 35.9 nmol/L after each mock ultrasonographic procedure and remained low for the duration of the LDDST. In phase 2, all dogs had significant increases in cortisol concentrations immediately after the mock ultrasonographic procedure. CONCLUSIONS AND CLINICAL RELEVANCE: A 20-minute mock abdominal ultrasonographic examination performed during LDDST did not alter results of the LDDST in most dogs. Cortisol concentrations measured immediately after a mock ultrasonographic examination were significantly increased. Ultrasonographic procedures should be performed a minimum of 2 hours before collection of samples that will be used to measure cortisol concentrations.     

Biochemical characterisation of navicular hyaline cartilage,navicular fibrocartilage and the deep digital flexor tendon in horses with navicular disease

The study hypothesis was that navicular disease is a process analogous to degenerative joint disease, which leads to changes in navicular fibrocartilage and in deep digital flexor tendon (DDFT) matrix composition and that the process extends to the adjacent distal interphalangeal joint. The objectives were to compare the biochemical composition of the navicular articular and palmar cartilages from 18 horses with navicular disease with 49 horses with no history of front limb lameness, and to compare navicular fibrocartilage with medial meniscus of the stifle and collateral cartilage of the hoof. Cartilage oligomeric matrix protein (COMP), deoxyribonucleic acid (DNA), total glycosaminoglycan (GAG), metalloproteinases MMP-2 and MMP-9 and water content in tissues were measured. Hyaline cartilage had the highest content of COMP and COMP content in hyaline cartilage and tendon was higher in lame horses than in sound horses (p<0.05). The concentration of MMP-2 amount in hyaline cartilage was higher in lame horses than in sound horses. The MMP-2 amounts were significantly higher in tendons compared to other tissue types. Overall, 79% of the lame horses with lesions had MMP-9 in their tendons and the amount was higher than in sound horses (p<0.05). In horses with navicular disease there were matrix changes in navicular hyaline and fibrocartilage as well as the DDFT with potential implications for the pathogenesis and management of the condition.