Metabolic profiling of ‘Conference’ pears under low oxygen stress     

Romina Pedreschi  Christine Franck  Jeroen Lammertyn  Alexander Erban  Joachim Kopka  Maarten Hertog  Bert Verlinden  Bart Nicolaï 《Postharvest Biology and Technology》2009,51(2):123-130

Pears (Pyrus communis L. cv. Conference) may develop core breakdown when stored under low oxygen or elevated carbon dioxide conditions. This physiological disorder is characterized by the development of brown spots due to oxidation of phenolic compounds, and eventually, cavities in the center of the fruit. Based on metabolic profiling of brown and sound tissue using GC-EI-TOF-MS, the hypothesis that this disorder is due to an imbalance between oxidative and reductive processes at the cellular level was investigated. Brown tissue was clearly characterized by a distinctive pattern in changes which included a decrease of malic acid and an increase in fumaric acid and gamma aminobutyric acid (GABA), which indicated a reduced metabolic activity at the level of the Krebs cycle and a putative block of the GABA shunt pathway. Increased gluconic acid concentration might be related to ascorbic acid degradation due to insufficient reducing equivalents or to an impaired pentose phosphate pathway. For the first time, GABA and gluconic acid have been shown to be metabolic markers for core breakdown. The concentrations of other compounds which are believed to be related to hypoxic stress response such as trehalose and putrescine were also considerably higher in brown tissue than in sound tissue. The concentration of some sugars which are typically found in xyloglucans also increased during brown development, possibly indicating cell wall breakdown due to enzymatic processes or chemical reactions of hydroxyl radicals.  相似文献   

Modelling the transient effect of 1-MCP on ‘Hass’ avocado softening: A Mexican comparative study     

Salvador Ochoa-Ascencio  Maarten L.A.T.M. Hertog  Bart M. Nicolaï 《Postharvest Biology and Technology》2009,51(1):62-72

In this study the effect of 1-methylcyclopropene (1-MCP) on the softening of avocado fruit (Persea americana Mill.) cv. Hass was modelled. Data were collected throughout the 2006 season by sampling 40 batches of fruit from 8 different commercial orchards in the region of Michoacan (Mexico). A simplified mechanistic model was developed to analyse the experimental data. Most of the model parameters were treated as being generic for all fruit while only two of the model parameters were identified as being unique to each individual fruit. The two fruit specific parameters characterised the maturity at harvest of an individual fruit and the sensitivity of an individual fruit to 1-MCP. Monte Carlo simulations were performed. The model was able to describe the individual fruit behaviour very well explaining more than 95% of the observed variation for most of the fruit. The model successfully quantified the effect of 1-MCP on avocado softening taking into account the stochastic nature of batch behaviour. The developed model can be utilised to predict the behaviour of a specific batch of ‘Hass’ avocado fruit given the distribution of the two fruit specific model parameters.  相似文献   

The role of brash in augmenting forest site carbon capital and maintaining site nutrition in a Sitka spruce forest in Ireland     

Samuel O. Olajuyigbe  Brian Tobin  Maarten Nieuwenhuis 《European Journal of Forest Research》2014,133(3):563-572

The decomposition of harvest residues (brash) in managed forests has an important influence on the carbon (C) and nitrogen (N) stocks of these ecosystems. The brash input from thinning events in a 25-year-old Sitka spruce plantation was determined. A litter-bag method was used to determine the mass loss and decomposition rate of brash left on the forest floor. The changes in C and N concentrations and the C:N ratio of the needles and branches were also monitored as decomposition progressed for 2.5 years. Using the decomposition rate (k _b) and estimated brash inputs, we then determined the total cumulative stock of C that the brash could supply to the deadwood pool over a 41-year rotation period. The three thinning events resulted in the addition of 37.99 t C ha^?1 and 0.61 t N ha^?1 to the forest floor. A significant mass loss of 44 % was recorded from brash decomposition bags after 2.5 years, with a rapid loss of 35 % in the first year, after which the rate of decomposition slowed. The k _b-value and residence time (95 % decomposition) were 0.311 year^?1 and 9.6 years, respectively. There was a 69 % increase in the N concentration of needles after 1.5 years, while an increase of 185 % in the N concentration of branches was recorded after 2.5 years. The C concentration (48.55 ± 0.20 %) did not differ significantly between the needles and branches over time. The accumulated C stock from decomposing brash at clearfell was estimated at 18.51 t C ha^?1.  相似文献   

Distribution and ecology of the Belgian Campodea species (Diplura: Campodeidae)     

Koen Lock  Tim Adriaens  Maarten Stevens 《European Journal of Soil Biology》2010,46(1):62-65

From 2004 till 2008, Diplura were sampled at 96 localities in Belgium. Nine different species of Campodea were collected: Campodea fragilis Meinert 1865, Campodea lankesteri Silvestri 1912, Campodea lubbocki Silvestri 1912, Campodea meinerti Bagnall 1918, Campodea plusiochaeta Silvestri 1912, Campodea remyi Denis 1930, Campodea rhopalota Denis 1930, Campodea staphylinus Westwood 1842 and Campodea wallacei Bagnall 1918. The ordination technique non-metric multidimensional scaling indicated that pH and temperature/humidity were probably the most important variables determining species composition. However, it was remarkable that almost all combinations of species were encountered in the field, often even under the same stone. As no temporal segregations seem to take place, it remains unknown how these very similar species can occur together.  相似文献   

Risk management of paratuberculosis in dairy herds     

Weber MF 《Irish veterinary journal》2006,59(10):555-561

Risk management of paratuberculosis (Johne's disease) in a dairy herd requires an assessment of the likelihood of paratuberculosis occurring in the herd, the economic impact of paratuberculosis on the herd and an evaluation of measures that can be taken to reduce this likelihood and impact.The likelihood of paratuberculosis occurring in the herd is related to the regional herd-level prevalence of paratuberculosis and the herd management (e.g., introducing animals from other herds). The economic impact of paratuberculosis includes production losses due to subclinical and clinical cases, losses due to increased replacement of animals and costs of control measures. Furthermore, a reduction of the price of milk from infected herds might result from consumer concerns about the zoonotic potential of paratuberculosis.Measures that reduce the likelihood of paratuberculosis occurring in a herd and its impact include preventive management measures (e.g., closed herd management and an effective separation of susceptible young stock from adult cattle), test-and-cull schemes for known infected herds and quality assurance schemes for test-negative herds. Quality assurance schemes for test-negative herds, such as schemes for 'low-Map bulk milk' and 'Map-free' herds, aim at safeguarding or increasing the profitability of these herds.Keys to success of risk management of paratuberculosis include realistic expectations of the results of paratuberculosis control, quality assurance and control programmes that are appreciated by farmers and incentives for farmers to participate in such programmes.  相似文献   

Control of Xiphinema index populations by fallow plants under greenhouse and field conditions     

Villate L  Morin E  Demangeat G  Van Helden M  Esmenjaud D 《Phytopathology》2012,102(6):627-634

The dagger nematode Xiphinema index has a high economic impact in vineyards by direct pathogenicity and above all by transmitting the Grapevine fanleaf virus (GFLV). Agrochemicals have been largely employed to restrict the spread of GFLV by reducing X. index populations but are now banned. As an alternative to nematicides, the use of fallow plants between two successive vine crops was assessed. We selected plant species adapted to vineyard soils and exhibiting negative impact on nematodes and we evaluated their antagonistic effect on X. index in greenhouse using artificially infested soil, and in naturally infested vineyard conditions. The screening was conducted with plants belonging to the families Asteraceae (sunflower, marigold, zinnia, and nyjer), Poaceae (sorghum and rye), Fabaceae (white lupin, white melilot, hairy vetch, and alfalfa), Brassicaceae (rapeseed and camelina), and Boraginaceae (phacelia). In the greenhouse controlled assay, white lupin, nyjer, and marigold significantly reduced X. index populations compared with that of bare soil. The vineyard assay, designed to take into account the aggregative pattern of X. index distribution, revealed that marigold and hairy vetch are good candidates as cover crops to reduce X. index populations in vineyard. Moreover, this original experimental design could be applied to manage other soilborne pathogens.  相似文献   

Human α-defensin 6 promotes mucosal innate immunity through self-assembled peptide nanonets     

Chu H  Pazgier M  Jung G  Nuccio SP  Castillo PA  de Jong MF  Winter MG  Winter SE  Wehkamp J  Shen B  Salzman NH  Underwood MA  Tsolis RM  Young GM  Lu W  Lehrer RI  Bäumler AJ  Bevins CL 《Science (New York, N.Y.)》2012,337(6093):477-481

Defensins are antimicrobial peptides that contribute broadly to innate immunity, including protection of mucosal tissues. Human α-defensin (HD) 6 is highly expressed by secretory Paneth cells of the small intestine. However, in contrast to the other defensins, it lacks appreciable bactericidal activity. Nevertheless, we report here that HD6 affords protection against invasion by enteric bacterial pathogens in vitro and in vivo. After stochastic binding to bacterial surface proteins, HD6 undergoes ordered self-assembly to form fibrils and nanonets that surround and entangle bacteria. This self-assembly mechanism occurs in vivo, requires histidine-27, and is consistent with x-ray crystallography data. These findings support a key role for HD6 in protecting the small intestine against invasion by diverse enteric pathogens and may explain the conservation of HD6 throughout Hominidae evolution.  相似文献   

Iconic CO2 time series at risk     

S Houweling  B Badawy  DF Baker  S Basu  D Belikov  P Bergamaschi  P Bousquet  G Broquet  T Butler  JG Canadell  J Chen  F Chevallier  P Ciais  GJ Collatz  S Denning  R Engelen  IG Enting  ML Fischer  A Fraser  C Gerbig  M Gloor  AR Jacobson  DB Jones  M Heimann  A Khalil  T Kaminski  PS Kasibhatla  NY Krakauer  M Krol  T Maki  S Maksyutov  A Manning  A Meesters  JB Miller  PI Palmer  P Patra  W Peters  P Peylin  Z Poussi  MJ Prather  JT Randerson  T Röckmann  C Rödenbeck  JL Sarmiento  DS Schimel  M Scholze  A Schuh  P Suntharalingam 《Science (New York, N.Y.)》2012,337(6098):1038-1040

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Genetic analysis of resistance to bacterial leaf streak caused by Xanthomonas campestris pv. undulosa in bread wheat     

Etienne Duveiller  Maarten van Ginkel  Marja Thijssen 《Euphytica》1992,66(1-2):35-43

Summary The inheritance of resistance to bacterial leaf streak or black chaff of wheat was studied under field conditions, with an artificial epidemic of Xanthomonas campestris pv. undulosa. A complete series of crosses between five parents, differing in reaction to X. c. pv. undulosa, was generated. Disease was recorded at two different stages of growth. No evidence of cytoplasmic effect was found from the comparison between reciprocal F₁ crosses. The study of the F₃ generations attested that five genes were involved in resistance to bacterial leaf streak. Separate analyses carried out for the two scoring dates were mutually consistent: genotypes, number of genes, and their action and relative importance were verified. The genes differed in strength of expression of resistance. One of the two strongest genes, Bls1, is present in all three superior parents, Pavon 76, Mochis T88 and Angostura F88. Resistance was not complete, and proved to be stable over the season.  相似文献   

CIMMYT's approach to breed for drought tolerance   总被引：4，自引：0，他引：4  

Sanjaya Rajaram  Hans-Joachim Braun  Maarten van Ginkel 《Euphytica》1996,92(1-2):147-153

Summary About 32% of the 99 million ha wheat grown in developing countries experiences varying levels of drought stress. Three major drought types have been identified: Late drought (LD) is common in the Mediterranean region, early drought (ED) is found in Latin America and wheat is produced on residual soil moisture (RM) in the Indian subcontinent and part of Australia. Until 1983, CIMMYT selected all germplasm under near optimum conditions for its yield potential and tested only advanced lines under drought. In spite of many critics, this approach proved to be successful, since in the mid 80's CIMMYT germplasm was grown on 45% of the wheat area in LC with annual rainfall from 300–500 mm and on 21% in areas with less than 300 mm. Since 1983, CIMMYT's drought breeding methodology is to alternate segregating populations between drought stressed and fully irrigated conditions (FI) and to test advanced lines under a line source irrigation system. To compare the efficiency of these approach, yield of four, mostly leading varieties, from each of the regions with LD, ED, RM, and FI and twelve recent CIMMYT cultivars selected for high yield under FI and RM conditions (ALT) were compared under four different moisture regimes (FI, LD, ED, and RM) in 89–90 and 90–91 in Yaqui Valley, Mexico. Genotypic correlation between yield and days to flowering, days to maturity, height, grains m^-2, TKW, test weight and grain fill period were calculated.Mean grain yield of the four best lines in the ALT group was highest under all moisture stress regimes, followed by the FI-group. However, the highest yielding cultivar within each moisture regime was from the FI-group under FI, from the LD-group under LD, and from the ALT-group under ED and RM conditions. Estimates for genetic advance suggest that FI is the best environment for increasing grain yield even in all three drought environments. This indicates that yield potential per se is beneficial also in drought environments. The highest yield in drought environments was realized by the CIM cultivars selected under FI and RM. Simultaneous evaluation of the germplasm under near optimum conditions, to utilize high heritabilities and identify lines with high yield potential, and under stress conditions to preserve alleles for drought tolerance seem at present the best strategy.  相似文献