Symbioses: Plant, Animal, and Microbe Interactions
Cheeke, Tanya E. , Rosenstiel, Todd , Cruzan, Mitchell, B .
Transgenic Bt maize: An evaluation of nine different Bt maize isolines on arbuscular mycorrhizal fungi.
The relationship between genetically modified (GM) plants and arbuscular mycorrhizal fungi (AMF) is an important element of soil ecology research. Currently, 80% of all maize grown in the United States is genetically modified to express herbicide resistance, insecticidal traits derived from the soil bacterium Bacillus thuringiensis (Bt), or a combination of stacked traits. Transgenic crop cultivation continues to increase worldwide yet the effects of Bt crops on arbuscular mycorrhizal fungi are not fully understood. AMF are obligate plant symbionts that contribute to soil structure and nutrient cycling and benefit plants by increasing nutrient uptake, providing protection against root pathogens, and improving drought tolerance. While AMF are sensitive to a variety of factors in agricultural ecosystems, it is still not clear how AMF are affected by Bt crop cultivation. In this experiment we evaluated AMF colonization levels in nine different Bt maize isolines differing in number and type of engineered traits. Bt and non-Bt parental isolines were grown for 60 days under nutrient limited conditions using 50% local agricultural soil in the potting mix as the mycorrhizal inoculum. Results from this experiment revealed that eight of the nine Bt maize isolines had reduced AMF colonization. Five of the nine Bt isolines had significant reductions in total AMF colonization (all P < 0.04) and three had significant reductions in arbuscule formation (all P < 0.04). Because AMF are obligate symbionts that rely on a plant host for nutrition and reproduction, they may be more sensitive to changes in the physiology of the host plant or to accumulation of Bt toxin in the rhizosphere than other soil organisms. The long-term implications of Bt crop cultivation have yet to be established, however, a general reduction in AMF colonization of Bt plant roots may reduce the density of AMF propagules in the soil, impacting soil structure and function over time.
Our lab has a long history of incorporating undergraduates into research and has a successful recruiting program through the teaching labs at Portland State University. We also actively reach out to under-represented students through the McNair scholar program which introduces first-generation and low-income students, and/or members of under-represented groups to academic research. As the PhD student leading this project, I have mentored seven undergraduate researchers, two high school interns, one honors thesis student, and one McNair Scholar since 2006. This dissertation research continues to provide an opportunity for undergraduate researchers to gain practical research skills in the field and in the laboratory in preparation for future graduate studies or a career in the biological sciences.
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1 - Portland State University, Biology, PO Box 751, Portland, OR, 97207, USA
2 - Portland State University, Department of Biology, PO Box 751, Portland, OR, 97207, USA
3 - Portland State University, Department of Biology, P.O. Box 751, Portland, OR, 97207, USA
arbuscular mycorrhizal fungi
Presentation Type: Oral Paper:Papers for Topics
Location: 552A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 1:30 PM