The semidwarf trait is desired in cereal breeding programs for increased lodging resistance. We characterized 27 brachytic (brh) semidwarf mutants in barley (Hordeum vulgare L.) and located the genes on barley chromosome linkage maps. All brachytic genes were transferred into the two-rowed cultivar Bowman by backcrossing four to seven times and selecting for semidwarf plants. The brachytic lines were evaluated for 10 phenotypic traits: plant height, awn, peduncle, and rachis internode length, leaf length and width, lodging, grain yield, number of kernels per spike, and kernel weight. We intercrossed the lines to determine which mutants were at independent loci and which were alleles at the same locus. F2 populations from 18 brh semidwarfs were constructed for genetic mapping using simple sequence repeat (SSR) markers. The brachytic semidwarf near-isogenic lines were significantly shorter than their normal counterparts and most had lower yields (16/27); shorter awns (26/27), peduncles (26/27), and rachis internodes (24/27); and reduced kernel weight (22/27). Twelve of the lines had shorter penultimate leaves and 15 had reduced lodging. Four lines had increased kernels per spike, while one had fewer kernels per spike. Allelism tests and mapping comparisons indicated that the 27 semidwarfs comprise 18 independent genetic loci. SSR mapping placed these loci in five of the seven barley chromosomes. Knowledge of the effects and locations of these brachytic semidwarf genes will help barley breeders select appropriate lines for barley improvement.
Novel, environmentally friendly antimicrobial coatings containing tethered biocide moieties derived from the ubiquitous biocide, triclosan, were synthesized and characterized using a high-throughput workflow. Triclosan was first modified with an acrylate functionality and, subsequently, copolymerized with hydroxyethyl acrylate and butyl acrylate using conventional free radical polymerization to form an array of acrylic polyol terpolymers. The polyols were characterized using nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and gel permeation chromatography. Arrays of urethane coatings were produced from the array of acrylic polyol terpolymers and, subsequently, characterized using parallel dynamic mechanical thermal analysis, surface energy measurements, and various biological assays. The results of the biological assays showed that the coatings were effective toward inhibiting Staphylococcus epidermidis biofilm retention without leaching triclosan or other toxic components from the coating. The level of antimicrobial activity was found to increase with the content of triclosan moieties incorporated into the coating matrix. These results indicate that triclosan moieties tethered to a polymer matrix can impart antimicrobial properties via a contact-active, nonleaching (i.e., environmentally friendly) mechanism. Since S. epidermidis is one of the primary microorganisms associated with infection and failure of implanted medical devices, such as prosthetic heart valves, urinary catheters, and a variety of orthopedic implants, these coatings may have good potential for commercialization in some of these applications.
Many universities sponsor science research programs during the summer to provide hands-on laboratory experience to high school students and teachers. Our objective was to design a project that exposes the students to the full range of research, from developing and testing a hypothesis through presenting research results. The project goal is to demonstrate mapping of morphological traits using simple sequence repeat (SSR) markers. Students learn how to evaluate plants for morphological marker traits, extract DNA, conduct PCR (polymerase chain reaction) and gel electrophoresis, evaluate results, and conduct linkage analysis between traits and markers. Mapping data are presented for five of the barley (Hordeum vulgare L.) traits analyzed since 1997. The genes bracteatum (bra-a.001) and short awn (lks.o) were located on the short arm of chromosome 7H, the glossy phenotype conferred by cer-zv.268 was located near the centromere of chromosome 4H, fragile stem (fst2.b) was located near the centromere of chromosome 1H, and intermedium spike (int-h.42) was located on the short arm of chromosome 5H. The high school teachers have used their experiences to help teach genetics and molecular biology, and several have included the projects in their portfolio for an advanced degree. Many students have used their projects for science fairs and their experience to help obtain part-time jobs during their undergraduate studies. These experiments provide the necessary components of a successful research project for short-term programs and provide meaningful data to advance our ongoing projects, benefitting both the students and our laboratory.
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