Improving and predicting storability of Swedish apples with IAD and improved storage conditions

Only around 30% of the apples consumed in Sweden are produced within the country, even though many customers prefer locally produced fruit. One way to increase the availability of Swedish fruit is to reduce post-harvest losses to pathogens and disorders, which increase if fruit is not harvested at optimal maturity. This thesis examined ways of improving the storability of Swedish apples by reducing losses due to fungal decay and to the physiological disorder soft scald, and by using different measures for establishing optimal harvesting time for mid- and late-season cultivars.  Weather conditions were found to have an effect on the incidence of soft scald, with humidity and rain increasing the incidence in some cases. Rainy weather also increased fungal decay. Absorbance difference index (IAD) was shown to be correlated with harvest time, apple firmness and Streif index before harvest. The strength of correlations showed high between-cultivar and between-year variations. IAD was found to be a possible complement to existing maturity indices, but causes of variation in the accuracy of IAD as a predictor of maturity need to be identified. Controlled storage atmosphere was found to be the most effective measure to control soft scald, while delayed cooling had little effect. Fruit maturity had a significant effect on soft scald incidence in some cases, but not every year. A strong effect of year was seen in most measurements, e.g. for strength of correlations, soft scald incidence and fungal decay

Salmonella och verotoxinproducerande E. coli i färdigsallader

Färdigsallader är en produktgrupp som blir allt mer populär. Dessvärre har det på senare år förekommit ett antal utbrott där människor har smittats av tarmbakterier som Salmonella och verotoxinproducerande Escherichia coli i olika ouppvärmda produkter som till exempel böngroddar från Tyskland. I denna litteraturstudie undersöks vilka patotyper av E. coli och Salmonella som kan infektera människor och hur detta kan gå till. Det ges förslag för att minska smittspridningen. Särskilt fokus ges E. coli-patotyper som tillverkar verotoxiner eftersom dessa ger allvarliga symptom hos människor. De vanligaste verotoxinproducerande E. coli- och Salmonella-serovararna som finns på sallader identifieras också. Slutsatserna är att hygien under hela produktionskedjan är av största vikt men att det är efter skörd som den största spridningen sker. Riskfaktorer som tillsats av animaliska produkter, och förslag på hur dessa risker kan minimeras, diskuteras.Ready-to-eat salads are an increasingly popular commodity. It displays a convenient way to prepare a meal. However, in recent years there have been a number of disease outbreaks caused by enteric bacteria such as Salmonella spp. and E. coli. One example is the recent outbreak of E. coli O104:H4, which was caused by contaminated sprouts. The aim of this thesis was to find out which pathotypes of Salmonella and E. coli, which are the most dangerous and also to try to find ways to deal with them to decrease their numbers. The main focus will be on verotoxin-producing E. coli as they can cause potentially life threatening symptoms apart from the other pathotypes which usually cause less severe symptoms. The conclusions are that the most important measure to take is to make sure that a high level of hygiene is maintained throughout the postharvest chain. It is here the main transmission of bacteria between, for example, field grown leafy vegetables may occur

Effekten av domesticering på insektsresistens i bomull : bioassays med Spodoptera littoralis och Agriotes spp.

A plant's defensive ability against herbivore attack can be influenced by many different factors, one of them being domestication. During human selection to improve the yield of plants, the resistance against herbivore attack can have been lowered, due to a trade-off for use of resources between these traits in the plants. In this thesis I investigated the effect of domestication on resistance against herbivorous insects in cotton plants. I used different varieties and species of wild and domesticated cotton in three different experiments. A feeding assay was conducted, the mortality, development time and pupal weight of larvae of the Egyptian cotton leaf worm Spodoptera littoralis was studied. In a second experiment the preference of the root-feeding beetle Agriotes spp. was monitored in a two choice assay comparing domesticated cotton to other cotton varieties and species. The third part of the thesis was an odour collection from domesticated cotton plants induced by either S. littoralis larvae feeding on the leaves, Agriotes spp. feeding on the roots or a combination of damage from both species. The data show that there is a difference between cotton cultivars and that wild varieties delay development time compared to domesticated cotton. The feeding assay showed that the domesticated varieties Dpl 90 and Glandless cotton had significantly shorter development times than the undomesticated varieties (Tx 263, Tx 2259 and G. herbaceum) The two choice assay with Agriotes spp. larvae did not give any significant results most likely because of a low number of repetitions. Agriotes spp. did not prefer either domesticated nor undomesticated varieties of cotton. However, a trend in favor of the domesticated cotton variety could be observed. Finally, analysis of the odour collection demonstrates that plants induced by Spodoptera littoralis alone release higher amounts of the volatiles alpha pinene, 1S-beta pinene, myrcene and terpinolene than plants induced with either only Agriotes spp. or a combination of the two types of larvae. It may be that Agriotes spp. can manipulate the defence of the cotton plants. Another explanation is that the cotton plants cannot detect the Agriotes larvae. Also, there might have been a release of volatiles below ground that was not detected due to the layout of the experiment.Växters förmåga att försvara sig varierar beroende på många olika orsaker. En teori säger att domesticeringen av vissa växter har sänkt deras resistens mot herbivorer i en trade-off med andra egenskaper så som ökad skörd som människan selekterat fram. I det här arbetet har jag undersökt effekten av domesticering på resistensen mot växtätande insekter genom att använda sorter och arter av bomull i olika stadier av domesticering. Detta har gjorts i tre olika experiment. Först genomfördes ett utvecklingsexperiment i vilket jag studerade utvecklingen av larver av bomullsflyet, Spodopeta littoralis från ägg till förpuppning, samt puppornas vikt. Den andra delen var ett beteendeförsök där rotlevande larver från skalbaggarna Agriotes spp. fick välja mellan rotsystemen av olika bomullsplantor. En tredje del av arbetet var en insamling av växtdofter från bomullsplantor som inducerats antingen av S. littoralis, som ätit på bladen, Agriotes spp., som ätit på rötterna eller en kombination av skadorna från båda arterna. Mina data visar att det finns en skillnad mellan olika bomullssorter och att vildare sorter generellt har en högre resistens mot insektsangrepp än domesticerade sorter. De domesticerade sorterna Dpl 90 och glandless cotton gav en signifikant kortare utvecklingstid i utvecklingsexperimentet än de vilda sorterna Tx263, G. herbaceum och Tx 2259. Däremot var det inga signifikanta skillnader mellan bomullssorterna i vikten på pupporna mellan dieterna. Tvåvalstestet med Agriotes-larver gav inga signifikanta resultat vilket troligen berodde på ett för lågt antal av replikat. Jag fann dock en tydlig trend där larverna föredrog den domesticerade sorten Dpl 90 över alla andra testade sorter, förutom den vilda arten G.herbaceum. Analysen av insamling av växtdofter visar att plantorna som inducerats av S. littoralis reagerar starkare och har en högre avgivning av flyktiga ämnen såsom alpha pinene, 1S-beta pinene, myrcene och terpinolene än plantor som inducerats av endast Agriotes spp. eller med en kombination av de båda arterna. Möjligtvis kan Agrioteslarverna manipulera bomullsplantan så att den inte startar sitt inducerade försvar eller så kan bomullsplantan inte upptäcka dem. Möjligen har också flyktiga ämnen släppts ut från rötterna av bomullsplantorna vilket inte detekterats eftersom endast ämnen från överjordiska delar insamlades

Comparison between IAD and other maturity indices in nine commercially grown apple cultivars

To maintain storage potential as long as possible, it is important to harvest fruit at optimal maturity. Different maturity indices have been developed, including flesh firmness, soluble solids content, starch degradation, ethylene production, and respiration rate. However, many of them are destructive, time consuming, and may be require some laboratory equipment to perform. The portable device DA-meter (measuring index of absorption difference; IAD) can monitor the chlorophyll decline non-destructively in the field, and could potentially save time. To evaluate the IAD in comparison with other maturity indices, nine common commercial cultivars of apple were investigated in a three-year trial. Correlations between IAD and other maturity indices, especially starch degradation and ripening index by Streif were strong in most cultivars, though variation between years lead to weaker correlations were found last year of the trial. The strongest correlations were found between IAD and harvest date showing that IAD decreased with time in all investigated cultivars. Comparison between IAD and ripening index by Streif showed in some cases that the two indices decreased at the same time, suggesting that IAD could be used to monitor maturity when it is rapid. The suitability to use IAD as a maturity index seems to be cultivar-dependent. For cultivars having a more consistent pattern between years in the decrease of IAD, combined with relatively low variation in IAD at any given time, it could be a good complement to other commonly used maturity indices

Multiple factors affecting occurrence of soft scald and fungal decay in apple during storage

Some apple cultivars are highly susceptible to soft scald, a physiological disorder that can lead to large losses. The effect of harvest time, gradual cooling regimes and storage conditions on soft scald and fungal decay was investigated in two common apple cultivars, 'Aroma' and 'Frida' in a three year trial 2018-2020. Further, possible relationships between weather conditions during the growing season and 28 d before harvest and soft scald incidence along with fungal decay after storage were studied. The year with the highest rainfall had the highest incidence of soft scald and fungal decay. Our results suggest that the relative humidity during a period of 28 d before harvest was important for later development of soft scald in 'Frida', and together the results from 'Frida' and 'Aroma' showed a moderate correlation between relative humidity and soft scald. Gradual cooling showed conflicting results, and no treatment consistently lowered soft scald incidence. Gradual cooling led to inconclusive results, and storage in ambient air led to higher incidence of soft scald as compared to some investigated ULO storage conditions. Advanced maturity was associated with soft scald development and more fungal decay in one out of three years in 'Aroma', but did not affect incidence in 'Frida'. The etiology of soft scald seems to be dependent of multiple factors

New Gamma-Ray Contributions to Supersymmetric Dark Matter Annihilation

We compute the electromagnetic radiative corrections to all leading annihilation processes which may occur in the Galactic dark matter halo, for dark matter in the framework of supersymmetric extensions of the Standard Model (MSSM and mSUGRA), and present the results of scans over the parameter space that is consistent with present observational bounds on the dark matter density of the Universe. Although these processes have previously been considered in some special cases by various authors, our new general analysis shows novel interesting results with large corrections that may be of importance, e.g., for searches at the soon to be launched GLAST gamma-ray space telescope. In particular, it is pointed out that regions of parameter space where there is a near degeneracy between the dark matter neutralino and the tau sleptons, radiative corrections may boost the gamma-ray yield by up to three or four orders of magnitude, even for neutralino masses considerably below the TeV scale, and will enhance the very characteristic signature of dark matter annihilations, namely a sharp step at the mass of the dark matter particle. Since this is a particularly interesting region for more constrained mSUGRA models of supersymmetry, we use an extensive scan over this parameter space to verify the significance of our findings. We also re-visit the direct annihilation of neutralinos into photons and point out that, for a considerable part of the parameter space, internal bremsstrahlung is more important for indirect dark matter searches than line signals.Comment: Replaced Fig. 2c which by mistake displayed the same spectrum as Fig. 2d; the radiative corrections reported here are now implemented in DarkSUSY which is available at http://www.physto.se/~edsjo/darksusy

Early search for supersymmetric dark matter models at the LHC without missing energy

We investigate early discovery signals for supersymmetry at the Large Hadron Collider without using information about missing transverse energy. Instead we use cuts on the number of jets and isolated leptons (electrons and/or muons). We work with minimal supersymmetric extensions of the standard model, and focus on phenomenological models that give a relic density of dark matter compatible with the WMAP measurements. An important model property for early discovery is the presence of light sleptons, and we find that for an integrated luminosity of only 200--300 pb$^{-1}$ at a center-of-mass energy of 10 TeV models with gluino masses up to $\sim 700$ GeV can be tested.Comment: 28 pages, 12 figures; published versio

WIMP Mass Determination with Neutrino Telescopes

Weakly-interacting massive particles (WIMPs) annihilating in the center of the Sun or the Earth may give rise to energetic neutrinos which might be discovered by astronomical neutrino detectors. The angular distribution of the neutrino-induced muons is considered in detail via Monte Carlo simulations. It is shown that large underground \v{C}erenkov neutrino telescopes might be able to extract the WIMP mass from the width of the muon angular distribution.Comment: 8 pages, latex, 7 uuencoded Postscript figure

Positron Propagation and Fluxes from Neutralino Annihilation in the Halo

Supersymmetric neutralinos are one of the most promising candidates for the dark matter in the Universe. If they exist, they should make up some fraction of the Milky Way halo. We investigate the fluxes of positrons expected at the Earth from neutralino annihilation in the halo. Positron propagation is treated in a diffusion model including energy loss. The positron source function includes contributions from both continuum and monochromatic positrons. We find that, for a "canonical" halo model and propagation parameters, the fluxes are generally too low to be visible. Given the large uncertainties in both propagation and halo structure, it is however possible to obtain observable fluxes. We also investigate the shapes of the positron spectra, including fits to a feature indicated by the results of the HEAT experiment.Comment: 16 pages, 19 figures, uses revte

Heavy Quark Photoproduction in Ultra-peripheral Heavy Ion Collisions

Heavy quarks are copiously produced in ultra-peripheral heavy ion collisions. In the strong electromagnetic fields, c c-bar and b b-bar are produced by photonuclear and two-photon interactions; hadroproduction can occur in grazing interactions. We present the total cross sections, quark transverse momentum and rapidity distributions, as well as the Q Q-bar invariant mass spectra from the three production channels. We consider AA and pA collisions at the Relativistic Heavy Ion Collider and Large Hadron Collider. We discuss techniques for separating the three processes and describe how the AA to pA production ratios might be measured accurately enough to study nuclear shadowing.Comment: Minor changes to satisfy referees and typo fixes; 52 pages including 17 figure