Genetically transformed Vaccinium macrocarpon `Stevens' and `Pilgrim' plants have been obtained using electric discharge particle acceleration. Three foreign genes, kan encoding a selectable marker, gus a reporter gene, and B.t.k. conferring lepidopteran resistance, were incorporated into the genome. Expression of kan was assayed by culturing shoots in vitro on media with several concentrations of kanamycin. Expression among transformed clones (transclones) varied from high resistance (normal growth at 300 mg/L kan) to no resistance. Histochemical analyses for gus expression revealed variability among transclones. Some transclones exhibited no gus expression, others had consistent area-specific expression while others displayed random expression. In preliminary feeding trials with blackheaded fireworm larvae, B.t.k. expression was found to be ineffective at controlling insect development. We have recovered plants transformed with a different promoter driving the B.t.k. gene in an effort to enhance expression.
Rod Serres, David Russell, Dan Mahr, and Brent McCown
Gail R. Nonnecke, Lee-Ann M. Kastman, and David R. Russell
A 200-level course at Iowa State Univ., Principles of Horticulture, has included a communication across the curriculum assignment for the past seven semesters involving ≈425 students. Each undergraduate student develops and writes an individual student newsletter on topics and for an audience of the student's choice. The semester-long project motivates students to practice a professional communication task, and teaches technical horticultural material and writing skills. The newsletters contain at least two separate articles for an intended audience, providing the students with an opportunity to learn technical information in subjects in which they are intensely interested, but may not be taught in a principles course. Drafts of the articles and newsletter project are peer-reviewed by the students to model the professional review process, provoke critical thinking, and provide students with more feedback than they would otherwise receive from the instructor alone. Additionally, peer-review facilitates writing intensive courses for the instructor who wishes to focus course activities on writing, but has limited time or resources for reviewing writing assignments. Student newsletter articles are selected to be included in quarterly department and extension newsletters, providing students with a real-world use of a communication across the curriculum assignment.
Jennifer Moore-Kucera, Anita Nina Azarenko, Lisa Brutcher, Annie Chozinski, David D. Myrold, and Russell Ingham
Organic growers are required to maintain or improve soil chemical, biological, and physical properties and thus need to integrate biological processes into fertility management. However, few guidelines exist for satisfying tree nutrient demands ecologically. Sound nitrogen (N) management is a key component for overall orchard productivity whereas poor N management may result in multiple environmental impacts, including runoff to surface or leaching to groundwater sources. Many growers substitute synthetic inputs with rapid-release, approved N fertilizers that have little effect on long-term soil health and fertility. The authors seek an alternative approach for synchronizing nutrient availability with tree demand that relies on managing soil biological communities to attain their maximum potential functionality and thus meet tree nutrient demand. This paper outlines a new conceptual framework with which to evaluate a variety of soil functions that are quantified using biological, microbial, and biochemical properties in relation to overall orchard performance. By combining information gathered from soil faunal indices (nematode community structure and diversity analyses) with data obtained by biochemical and microbial analyses of the soil samples, a new, in-depth view of soil communities and their response to management practices will be obtained. As a result, a better understanding of the effects of differing management practices on soil fertility and community structure will be gained. This approach is currently being investigated by our group in organic and integrative sweet cherry orchards. Our goal is to determine which soil parameters may be used to help orchardists optimize soil health while maintaining orchard productivity. Furthermore, we wish to validate a number of assumptions that are commonly made regarding each soil parameter tested across multiple management, soil, and climate types.
Rodney Serres, Elden Stang, Dennis McCabe, David Russell, Daniel Mahr, and Brent McCown
Genetic transformation of the American cranberry, Vaccinium macrocarpon Ait., was accomplished using electric discharge particle acceleration. Plasmid DNA containing the genes GUS (β-glucuronidase), NPTII (neomycin phosphotransferase II), and BT (Bacillus thuringiensis subsp. kurstaki crystal protein) was introduced into stem sections, derived from in vitro cultures, that had been induced to form adventitious buds. The stage of development of these adventitious buds was critical for efficient initial expression. After exposure to electric discharge particle acceleration, stem sections were cultured on a solid-phase bud-inducing medium containing 300 mg kanamycin/liter. In addition, a thin overlay of 300 mg kanamycin/liter in water was added to inhibit growth of nontransformed cells. Within 7 weeks, green shoots emerged amidst kanamycin-inhibited tissue. No escape (nontransformed) shoots were recovered, and 90% of the transformed shoots were shown through PCR and Southern blot analysis to contain all three introduced genes. GUS expression varied markedly among various transformed plants. Preliminary bioassays for efficacy of the BT gene against the feeding of an economically important lepidopteran cranberry pest have shown no consistently effective control. Potential problems with the expression of the BT and GUS genes are discussed