Effect of curing at different temperatures on biochemical composition of onion (Allium cepa L.) skin from three freshly cured and cold stored UK-grown onion cultivars

Onions are cured in order to form a complete, dry, outer skin which reduces water loss and suppresses incidence of disease, and can promote a darker skin finish. Currently in the UK, standard curing practises for onions involves heating at 28 °C for six weeks (65–75% RH), however, reducing curing temperatures may help to reduce energy usage. There is little empirical data on the effects of curing temperature on flavonol concentration in the skin of brown onions and on flavonol and anthocyanin concentration in the skin of red onions. Therefore, the aim of this study was to elucidate the compounds responsible for the change in onion skin colour when cured at different temperatures.Brown cvs. Sherpa and Wellington, and red onions cv. Red Baron, were cured at 20, 24 or 28 °C for six weeks. Replicated skin samples were analysed immediately after curing and after seven months cold storage at 1 ± 0.5 °C. Measurement of objective colour showed that skin of cvs. Sherpa and Wellington was darker and had a lower hue angle (H°) immediately after being cured at 28 °C compared to 20 °C. In contrast, skin of cv. Red Baron had a higher H° but no change in lightness (L*) when cured at 28 °C compared to 20 °C. Fructose, sucrose and glucose concentrations were analysed as they are thought to play a role in regulating the synthesis of flavonols and anthocyanins, both coloured compounds found in onion skin; however no significant correlations were found between colour data and sugar concentrations. Flavonols were measured in the skin of all cvs. and anthocyanins in the skin of cv. Red Baron. Quercetin glucoside and anthocyanin concentrations in the skin of onions cv. Red Baron immediately after curing were higher in those cured at 20 °C. Total flavonols and total anthocyanins were negatively correlated with H° in the skin of onions cv. Red Baron, but there was no similar correlation between total flavonols and H° for onion cvs. Sherpa and Wellington. This suggests that anthocyanins and flavonols may play a major role in varying skin colour of red onions cv. Red Baron cured at different temperatures; however, the difference between curing temperatures may not have been sufficient to represent a correlation between darkening of cvs. Sherpa and Wellington and flavonol concentration. Further investigation is therefore required to fully elucidate the compounds responsible for colour changes observed in brown onions.     

Model identification of the bundle thickness dynamics in drum friction spinning

The dynamics of the friction yarn formation process is described in terms of the dynamic behavior of the process state variables. Production efficiency and product quality of friction spinning are influenced by these process state variables. This study was performed with the intention of setting up a dynamic model based on mass balance in order to delineate the dynamic behavior of the cross-sectional area of the in-process bundle on the friction drum surface and to attain the distribution profiles of the cross-sectional area in transient state and in steady state as well. Then, simulation results were compared with those of the experiment, while the input variation was used as a test signal. Theoretical model shows that the bundle thickness on the friction drum has the dynamic characteristics of an integrating system with interval due to the finite length of the input fleece zone, and is in good correspondence with the results of the experiment. A periodic change in the fleece feeding rate led to the fact that there was a specific range of the fluctuation wavelength in the fleece feeding rate, whereas a change in the in-process bundle thickness completely disappeared or became locally maximized in certain wavelength areas. This could lead to a magnification or inaction of the perturbations with the corresponding wavelength in the bundle thickness; a bundle thickness irregularity. Experiments also identified that the theoretical model accurately described the fiber accumulation dynamics in a friction spinning process.     

Postharvest application of ethylene and 1-methylcyclopropene either before or after curing affects onion (Allium cepa L.) bulb quality during long term cold storage

The storability of onion bulbs is dependent on the incidence and rate of sprout growth. Exogenous ethylene applied continuously has been demonstrated to act as a sprout suppressant in onion. However, the ethylene binding inhibitor, 1-methylcyclopropene (1-MCP), can also suppress sprouting in onion. Given this seemingly contradictory result, the precise role that ethylene plays during onion storage and the effect of curing on its efficacy is not understood.‘Sherpa’ and ‘Wellington’ onion bulbs were treated before or after curing (28 °C for 6 weeks) with a single dose of 10 μL L⁻¹ ethylene or 1 μL L⁻¹ 1-MCP for 24 h at 20 °C, or no treatment (control). Replicated out-turns were sampled during 38 weeks storage at 0–1 °C. Sprout growth (31 weeks after harvest) was reduced in ‘Sherpa’ treated before curing with ethylene or before or after curing with 1-MCP. However, sprout growth of ‘Wellington’ was not affected by any treatment. Following treatment, the cured, thick-skinned ‘Wellington’ released a lower concentration of treatment gas compared with the newly harvested, thin-skinned ‘Sherpa’. Onion bulb respiration rate increased immediately after being treated with ethylene but to a lesser extent or not at all when treated with 1-MCP. Fructose concentrations of onions treated with ethylene or 1-MCP before curing were not significantly different, however, after curing concentrations were about 2-fold higher compared with the control. Mean glucose and sucrose concentrations for both cultivars were higher immediately after being treated before curing with ethylene or 1-MCP than control bulbs. It appears that inhibition of sprout growth can be achieved using just a short 24 h treatment with ethylene or 1-MCP. However, skin thickness or permeability, which is dependent on cultivar and curing, may affect ethylene or 1-MCP influx and therefore efficacy of sprout suppressant action.     

Experimental oral transmission of chronic wasting disease to red deer (Cervus elaphus elaphus): Early detection and late stage distribution of protease-resistant prion protein

Chronic wasting disease (CWD), an important emerging prion disease of cervids, is readily transmitted by intracerebral or oral inoculation from deer-to-deer and elk-to-elk, suggesting the latter is a natural route of exposure. Studies of host range susceptibility to oral infection, particularly of those species found in habitats where CWD currently exists are imperative. This report describes the experimental transmission of CWD to red deer following oral inoculation with infectious CWD material of elk origin. At 18 to 20 months post-inoculation, mild to moderate neurological signs and weight loss were observed and animals were euthanized and tested using 3 conventional immunological assays. The data indicate that red deer are susceptible to oral challenge and that tissues currently used for CWD diagnosis show strong abnormal prion (PrP^CWD) accumulation. Widespread peripheral PrP^CWD deposition involves lymphoreticular tissues, endocrine tissues, and cardiac muscle and suggests a potential source of prion infectivity, a means of horizontal transmission and carrier state.     

Targeted identification of genomic regions using TAGdb

Background

The introduction of second generation sequencing technology has enabled the cost effective sequencing of genomes and the identification of large numbers of genes and gene promoters. However, the assembly of DNA sequences to create a representation of the complete genome sequence remains costly, especially for the larger and more complex plant genomes.

Results

We have developed an online database, TAGdb, that enables researchers to identify paired read sequences that share identity with a submitted query sequence. These tags can be used to design oligonucleotide primers for the PCR amplification of the region in the target genome.

Conclusions

The ability to produce large numbers of paired read genome tags using second generation sequencing provides a cost effective method for the identification of genes and promoters in large, complex or orphan species without the need for whole genome assembly.     

Crop species differ in root plasticity response to localised P supply

The effect of localised phosphorus (P) fertiliser placement and in particular, deep P fertiliser placement, on the comparative root growth and P uptake of fibrous vs tap‐rooted crops is not known. In this study, we examined the root growth and P uptake of wheat (Triticum aestivum L.), canola (Brassica napus L.), and narrow‐leaf lupin (Lupinus angustifolius L.) in a split‐root system and in columns with deep (19 cm) or shallow (5 cm) P fertiliser sources in glasshouse conditions. In the split‐root system, plants of all three species grown under heterogeneous soil P conditions absorbed more P and produced greater root and shoot biomass than those under homogeneous P supply. Root plasticity differed between species under heterogeneous soil P supply: canola and wheat allocated relatively more root biomass and root length to the high P zone than narrow‐leaf lupin. In the column experiment, there was no difference in the amount of P accumulated in shoots of any crops grown in the deep vs shallow P fertiliser treatments. Root proliferation occurred within the shallow and deep‐P fertiliser bands in all three species; however, root distribution above or below the bands did not differ between deep or shallow P fertiliser treatments in any species. Whilst root plasticity responses to heterogeneous soil P supply differed among species, root architecture (fibrous vs taproot) did not confer any advantage or disadvantage to the acquisition of P from deep vs shallow P fertiliser bands. Moreover, whilst roots proliferate in the vicinity of P fertiliser bands, root distribution outside of the bands appears to remain unaltered in both fibrous and tap‐rooted crops during early growth.