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Browsing by Author "Barbeau, Adam"

Now showing 1 - 3 of 3
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    Analysis of Natural Antimicrobial Extracts of Rhus typhina Found in Minneapolis
    (2012-04-18) Barbeau, Adam
    Plants produce numerous organic compounds that have antimicrobial activity. (Borchardt, 2008b; Gillitzer et al. in review) These natural products are found in tissues and structures throughout the plant, including the stems, berries, mature/young leaves, and roots. The many native and naturalized plant species that grow throughout Minnesota are a potential source of chemicals with antimicrobial properties that could be useful in medicines, cosmetics, preservatives or pesticides. Identification of antimicrobial compounds from a wide array of plant tissues and numerous plant species requires screening of numerous extracts from many different plant sources for their biological activity. Alamar Blue (AB), a nontoxic, water soluble dye, changes color from indigo blue to fluorescent pink in the presence of living cells. This color change is an accurate indicator of the fungistatic activity of plant extracts, via respiration, dissolved in a solution of water, nutrient broth, and AB. Phytopthora sojae is a soil borne plant pathogen and major cause of soybean crop loss. Zoospores are a motile reproductive stage of P. sojae critical to the infection process.
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    Does Fusarium solani Form an Endophytic Association with Soybean Roots?
    (2013-04-20) Barbeau, Adam
    Fusarium solani (F. solani) is a soil-borne filamentous fungus which causes seed and seedling rot in soybean (Glycine max). Infection during germination can cause severe stand reductions. However, if a soybean seedling is able to survive through the initial infection the plant tends to be larger in size and produces higher yield. The objective of this research is to determine if infection by F. solani persists in the soybean roots after initial infection. Seedlings were grown in soil inoculated with uninfested and infested red sorghum for 28 days. Three observation techniques, plating, staining, and quantitative PCR (qPCR) using primers specific for F. solani, were conducted on roots after the plants were harvested. When roots were plated on ampicillin rifampicin infused water agar (ARWA) media there was general contamination of the roots with what appears to be Pythium spp., a fungus-like genus which interferes with the growth of filamentous fungi. This contamination may also complicate microscopic assessment of fungal infection of stained roots due to our inability to distinguish hyphae of F. solani from those of Pythium spp. Use of specific primers allowed us to detect F. solani in the sampled roots; however, competition with Pythium spp. compromised our results. Use of selective culture media and sterilization of growth media may be necessary to prevent the growth of contaminating Pythium spp.
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    SPURIOUS SYMPTOMS CAUSED BY INOCULUM CARRIERS USED IN PLANT DISEASE RESISTANCE EVALUATION
    (2013-04-20) Barbeau, Adam
    Symptom development resulting from inoculation and infection with plant pathogens is necessary in order to evaluate plants for disease resistance. The standard technique for infecting soybean (Glycine max) with Fusarium solani, a root rot pathogen, involves inoculation of growth media with infested seed as an inoculum substrate carrying the pathogen. It has been reported that some uninfested substrates can have adverse effects upon shoot growth and root development. These effects also include lesion-like necrosis similar to that caused by soybean root rot pathogens. The objective of our research is to determine if uninfested inoculum substrate affects soybean shoot or root growth and root symptom development. Soybean seeds were planted in media inoculated with seed of red sorghum, white sorghum, or sudan grass that had been infested with Fusarium solani or remained uninfested. After 14 days of growth, foliar and root necrosis scores, shoot and root dry weights, and stand counts were evaluated. When the effect of uninfested seed was compared with that of infested seed, the uninfested treatment caused more severe root rot symptoms and decreased shoot and root biomass by 20% and 15% respectively. Our results indicate that the uninfested inoculum substrate can cause both spurious growth reduction and symptom development that may mislead the researcher conducting soybean variety evaluations for disease resistance.