High-throughput screening reveals small molecule modulators inhibitory to Acidovorax citrulli

Acidovorax citrulli is a seed-transmitted gram-negative bacterium that can cause substantial economic yield loss in watermelon and melon production worldwide. Four small-molecule libraries containing 4,952 compounds were selected for high-throughput screening against A. citrulli wild-type strain Xu3-14 by evaluation of growth inhibition. One hundred and twenty-seven molecules (2.5% hit rate) were identified as bactericidal or bacteriostatic against A. citrulli at 100 μM. Secondary screens indicated that 27 candidate compounds were more effective against A. citrulli Group II strains than Group I strains (classified using repetitive element PCR). Several compounds were inhibitory to other pathogenic bacteria, including Clavibacter michiganensis subsp. michiganensis and Xanthomonas campestris pv. campestris, but did not affect the growth of plant beneficial bacteria Pseudomonas fluorescens and Bacillus subtilis. More than half of the compounds did not inhibit germination of Arabidopsis or watermelon seeds. The effect of small molecules on A. citrulli seed-to-seedling transmission was evaluated by applying each compound to inoculated watermelon seeds and assessing seedling infection. Nine compounds were chosen for further investigation based on their reduction of percentage seedling infection and compiling scores on their specificity, sensitivity, and phytotoxicity obtained in the secondary screens. The five best compounds were selected (thiamphenicol, nadifloxacin, pipemidic acid, ciclopirox, and zinc pyrithione) for greenhouse tests and were found to effectively reduce the seed-to-seedling transmission of A. citrulli in both artificially and naturally infested seeds. These top five compounds provide a basis for future development of an A. citrulli-specific bactericide.     

Strategy to identify resistance to white mould associated with high yield for irrigated common bean in Brazil

Development of common bean cultivars with partial white mould resistance through breeding techniques has been a challenge in Brazil. As yet, lines/cultivars from breeding programmes have not been investigated for resistance; therefore, this study screened 107 lines/cultivars for their reactions to white mould in 14 preliminary trials conducted under irrigation. Thirteen resistant lines/cultivars (three of Andean origin) and six Mesoamerican cultivars (three intermediately resistant and three susceptible) were selected for further investigation. These lines/cultivars and the resistant control A195 were evaluated in six advanced trials and two straw tests to assess the effectiveness of the screening procedure. In 11 preliminary trials, screenings were performed under moderate/high or higher disease pressure. These pressures occurred in two advanced trials in which, when yields were averaged across moderate/high and high pressures, 10 Mesoamerican lines/cultivars selected for resistance yielded 14%, 23%, and 38% more than intermediately resistant cultivars, A195, and susceptible cultivars, with median disease ratings (1–9 scale) of 4.5, 5.7, 5.7, and 6.7, respectively. In the straw test, three Andean lines/cultivars (A195 included) and two susceptible cultivars in the field were among those with the highest levels of physiological resistance. Thus, field rating under high disease pressure and greenhouse rating did not correlate significantly, suggesting that field trials are critical to evaluating resistance and to identifying high-yielding beans. Therefore, lines/cultivars from breeding programmes assessed in field trials may provide a low cost and fast way to identify high-yielding bean cultivars with partial resistance to white mould in the subtropical southern hemisphere.     

Isolating the effect of soil properties on agricultural soil greenhouse gas emissions under controlled conditions

Agricultural soils are important sources of greenhouse gases (GHGs). Soil properties and environmental factors have complex interactions which influence the dynamics of these GHG fluxes. Four arable and five grassland soils which represent the range of soil textures and climatic conditions of the main agricultural areas in the UK were incubated at two different moisture contents (50 or 80% water holding capacity) and with or without inorganic fertiliser application (70 kg N ha⁻¹ ammonium nitrate) over 22 days. Emissions of N₂O, CO₂ and CH₄ were measured twice per week by headspace gas sampling, and cumulative fluxes were calculated. Multiple regression modelling was carried out to determine which factors (soil mineral N, organic carbon and total nitrogen contents, C:N ratios, clay contents and pH) that best explained the variation in GHG fluxes. Clay, mineral N and soil C contents were found to be the most important explanatory variables controlling GHG fluxes in this study. However, none of the measured variables explained a significant amount of variation in CO₂ fluxes from the arable soils. The results were generally consistent with previously published work. However, N₂O emissions from the two Scottish soils were substantially more sensitive to inorganic N fertiliser application at 80% water holding capacity than the other soils, with the N₂O emissions being up to 107 times higher than the other studied soils.     

Effects of a highly purified fucoidan from Undaria pinnatifida on growth performance and intestine health status of gibel carp Carassius auratus gibelio

A six‐week feeding trial was conducted to determine the effects of different concentrations of fucoidan (1 g/kg, 10 g/kg and 30 g/kg; w/w) from Undaria pinnatifida on gibel carp (Carassius auratus gibelio). Our results demonstrated that 30 g/kg fucoidan significantly increased (p < .05) growth performance, intestinal digestive enzyme activities, acid phosphatase activity and immunoglobulin M content. Histological examinations revealed that gibel carp receiving 30 g/kg fucoidan had significant higher abundance of mucin‐containing goblet cells in middle and distal intestine as compared with control treatment (p < .05). Intestinal microbiota analysis showed that 30 g/kg fucoidan supplementation significantly increased (p < .05) the abundance of Cetobacterium and Aeromonas, but lowered (p < .05) the prevalence of pathogenic bacteria Plesiomonas and a mucin‐degrading bacterium Mucinivorans. Furthermore, RNA‐seq and RT‐qPCR analysis indicated that 30 g/kg fucoidan caused significant changes (p < .05) in the expression of genes involved in immune regulation (such as interleukin‐8 and cyclooxygenase), signal transduction (such as phosphatidylinositol‐4,5‐bisphosphate 3‐kinase and protein kinase B) and nutrition utilization (maltase–glucoamylase and muscarinic acetylcholine receptor 3). Together, the current study shows that fucoidan supplementation could elevate the activity of intestinal digestive enzymes, modulate intestinal microbial communities and potentiate a higher state of immune readiness, which might consequently improve growth performance and intestine health status of gibel carp.     

Seasonal movements of immature Kemp's ridley sea turtles (Lepidochelys kempii) in the northern gulf of Mexico

1. Seasonal movements and core habitat areas of immature Kemp's ridley sea turtles (Lepidochelys kempii) in the northern Gulf of Mexico were tracked via satellite telemetry. Tagged turtles were incidentally captured by recreational fishermen and rehabilitated at the Institute for Marine Mammal Studies in Gulfport, Mississippi.
2. The average size of the core habitat areas (50% KDE (kernel density estimation)) was 1660.2 km² ± 3438.2 SD. Turtles displayed strong intra‐ and inter‐annual site fidelity to the Mississippi Sound during the spring, summer, and autumn months. During the winter months, most turtles, probably influenced by water temperatures, migrated to nearshore waters of Louisiana on either side of the Mississippi River Delta. However, other migration strategies were also observed.
3. Overall, these data indicate that the Mississippi Sound is an important developmental habitat for this critically endangered species. In addition, their wintering grounds in Louisiana are utilized by adult Kemp's ridleys and other sea turtle species as foraging grounds and migratory corridors. The high use of these areas by sea turtle populations increases the potential for negative impacts from anthropogenic disturbances (e.g. shrimp trawling, oil production, hypoxia) that occur there.

Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of an intensive mechanical removal effort on a population of non‐native rainbow trout Oncorhynchus mykiss in a South African headwater stream

1. Invasions by non‐native species can compromise the conservation value of otherwise pristine headwater streams. While both developed and developing countries recognize this threat, few of the latter have suitable budgets to implement control programmes.
2. This study assessed the effectiveness of a mechanical project to remove non‐native rainbow trout Oncorhynchus mykiss from a 6 km section of the upper Krom River, a small headwater stream in the Cederberg Mountains in South Africa's Cape Floristic Region (CFR).
3. From October 2013 to February 2014, 354 O. mykiss were removed by angling (58%), fyke netting (28%) and gill netting (14%). This resulted in a marked reduction, but not eradication, of the O. mykiss population (fish relative abundance decreased from 0.53 ± 0.09 fish per net per night in October 2013 to 0.21 ± 0.09 fish per net per night in February 2014). Following the cessation of manual removals, the relative abundance of O. mykiss had increased to 0.56 ± 0.18 fish per net per night by March 2016, suggesting that without sustained removal effort, the population will rapidly return to its pre‐removal abundance level.
4. Further work is needed to refine the methodology and test the effectiveness of mechanical removal of non‐native freshwater fish in a variety of ecological settings in the CFR. This approach holds potential for meeting the dual goals of reducing the ecological impacts of non‐native fishes and generating employment opportunities in line with the policy objectives of developing nations.

     

Development of multiple cutaneous and follicular neoplasms associated with canine papillomavirus type 3 in a dog

A 12‐year‐old spayed English pointer dog developed multiple skin lesions including pigmented viral plaques, basal cell carcinomas, squamous cell carcinomas and trichoblastomas. Canine papillomavirus type 3 was detected in multiple lesions suggesting common aetiology.

     

Role of social structure in establishment of an invasive large mammal after translocation

Background

Data on the movement behavior of translocated wild pigs is needed to develop appropriate response strategies for containing and eliminating new source populations following translocation events. We conducted experimental trials to compare the home range establishment and space-use metrics, including the number of days and distance traveled before becoming range residents, for wild pigs translocated with their social group and individually.

Results

We found wild pigs translocated with their social group made less extensive movements away from the release location and established a stable home range ~5 days faster than those translocated individually. We also examined how habitat quality impacted the home range sizes of translocated wild pigs and found wild pigs maintained larger ranges in areas with higher proportion of low-quality habitat.

Conclusion

Collectively, our findings suggest translocations of invasive wild pigs have a greater probability of establishing a viable population near the release site when habitat quality is high and when released with members of their social unit compared to individuals moved independent of their social group or to low-quality habitat. However, all wild pigs translocated in our study made extensive movements from their release location, highlighting the potential for single translocation events of either individuals or groups to have far-reaching consequences within a much broader landscape beyond the location where they are released. These results highlight the challenges associated with containing populations in areas where illegal introduction of wild pigs occurs, and the need for rapid response once releases are identified. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Challenges of thermal nociceptive threshold testing in the donkey

ObjectiveTo evaluate a thermal nociceptive threshold (TNT) testing device in the donkey, and the influence of potential confounding factors on TNTs.AnimalsTwo groups (Group 1 and Group 2) of eight castrated male donkeys aged 4–9 years, weighing 105–170 kg.MethodsTNTs were measured by heating a thermal probe on skin until an end-point behaviour (threshold temperature) or a cut-out temperature (51 °C) was reached. The withers and the dorsal aspect of the distal limb were used as sites for TNT testing. The effects on TNT of different confounding factors: the limb tested; rate of heating; and ambient temperature were evaluated. Data were analyzed using general linear models, and Mann-Whitney tests, p < 0.05 was considered significant.ResultsEnd-point behaviours (skin twitch or donkey looking at test device) when the thermal probe heated the withers were observed in approximately half of tests. TNT was (mean ± SD) 46.8 ± 2.85 °C. Subsequently the limb was evaluated as the test site in Group 1 followed by Group 2 donkeys; end-point behaviour being a foot-lift. In Group 1, 72% of tests ended in an end-point behaviour but the response rate was lower in Group 2 (20%), although TNTs were similar [(47.6 ± 3.3) and (47.3 ± 3.0) °C respectively] for responding animals. Rate of heating, ambient temperature and laterality (right or left) did not affect thresholds, but mean TNT was significantly higher in the forelimb (48.5 ± 2.8 °C) than the hind limb (47.4 ± 2.8 °C) (p = 0.012).ConclusionsWhen a thermal probe cut-out temperature of 51 °C was used in TNT testing in the donkey a high proportion of tests did not produce an identifiable end point behaviour. Higher cut-out temperatures damaged the skin. Under these conditions, thermal nociceptive threshold testing appears not be an appropriate analgesiometry technique in the donkey.Clinical relevanceTNT testing under these conditions is not suitable form of analgesiometry for donkeys.