UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Evaluation of Raspberry (Rubus sp.) Genotypes for Postharvest Quality and Resistance to Botrytis cinerea
    (2012) Harshman, Julia Mae; Walsh, Chris S; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Raspberries are a delicate, high value specialty crop with an extremely short shelf life. This is exacerbated by their susceptibility to postharvest decay caused by Botrytis cinerea. Of the three commercially available species, red raspberry (Rubus idaeus L.) is the most widely grown. Yellow (R. idaeus L.), black (R. occidentalis L.) and purple raspberries (R. × neglectus Peck.) are mainly available from direct marketers. The quality and storageability of 17 cultivars was examined weekly from June to September during two growing seasons. Storage life was assessed weekly, while firmness, color, respiration and ethylene evolution rates were measured in select harvests. Black and purple raspberries outperformed red and yellow cultivars in their ability to resist B. cinerea colonization. Black raspberries also had the lowest ethylene evolution rates and incidence of decay. This information will be useful to raspberry breeding programs by identifying physiological characteristics that are correlated with greater resistance to B. cinerea.
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    COMPARATIVE ECOLOGY OF THE INVASIVE RUBUS PHOENICOLASIUS AND THE NATIVE RUBUS ARGUTUS
    (2005-05-26) Innis, Anne Foss; Forseth , Irwin N; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Invasive species are one of the most significant factors in human influenced global change. Management actions that prevent the spread and impacts of invasive species require knowledge of their ecological characteristics. The characteristics of the invasive wine raspberry (Rubus phoenicolasius Maxim.) and the native sawtooth blackberry (Rubus argutus Link) were examined in two forest habitats on the Maryland Coastal Plain. The invasive had greater negative effects on a common herbaceous plant (Duchesnea indica Andr. Focke) than the native. The invasive, R. phoenicolasius had higher leaf nitrogen concentrations (Nleaf), greater specific leaf areas (SLA) and higher maximal rates of photosynthesis (Amax) for a given dark respiration rate (Rd) than R. argutus. R. phoenicolasius depended less upon pollinators for fruit development and had higher fruiting rates with more seeds per fruit than the native species. In addition, seeds of R. phoenicolasius had higher germination rates. Survival of invasive seedlings was negatively affected by leaf litter additions, but seedling growth was not negatively influenced by shading. R. phoenicolasius seedlings grown in a greenhouse and inoculated with arbuscular mycorrhizal fungi produced less biomass than seedlings that were not inoculated. The distribution of R. phoenicolasius may be affected by leaf litter, but presence of AMF is probably not necessary for seedling success. A three year demographic study showed that both species were negatively impacted by drought, but the invasive recovered faster than the native species in the higher light forest. Overall, results of these studies indicate that the invasive R. phoenicolasius was more likely to competitively exclude understory herbs which can coexist with the native R. argutus. The ability of R. phoenicolasius to adapt physiologically to different light levels helps explain its ability to form dense populations under varying environmental conditions. The combination of high fruit production, plasticity and lower mortality in high light habitats is in agreement with previous studies on invasive species. The combined characteristics demonstrated by R. phoenicolasius allow this invader to spread, expand and persist in mid-successional forests in the Coastal Plain of Maryland.