Determination of Chilling Requirement of Arkansas Thornless Blackberry Cultivars

Little research has been done to determine the chilling requirement for blackberry cultivars. However, field observations from areas where fewer hours of chilling occur indicate that ‘Navaho’ requires more hours of chilling than does ‘Arapaho’. The objective of our study was to determine a method for measuring the chilling requirement using whole plants of two blackberry cultivars, Arapaho and Navaho. One-year old, bare-root plants were field-dug on 26 October 1999 and placed in a cold chamber at 3ºC. Ten single-plant replications of each cultivar were removed at 100-hour intervals up to 1000 hours. The plants were potted and placed in a greenhouse (daily minimum temperature 15ºC), and plants were arranged on benches in a completely randomized design. Budbreak was recorded on a weekly basis. Data for budbreak were analyzed as a two-factor factorial (2 cultivars and 10 chilling treatments) by SAS and means were separated by least significant difference (P = 0.05). Data indicated that the chilling requirement for Arapaho is between 400 and 500 hours. For Navaho, the data indicated the chilling requirement was between 800 and 900 hours. These data support previous observations and indicate that the method used was successful in determining the chilling requirement for blackberries

Adventitious shoot propagation and cultural inputs in nursery production of a primocane-fruiting blackberry selection

Studies were conducted from January to October 2005 to determine the effect of root-cutting length on adventitious shoot yield and the management practices necessary to produce nurseryquality primocane-fruiting blackberry plants. The first portion of the study measured the average number of shoots produced from 7.6 cm- and 15.2 cm-long root cuttings of APF-44 blackberry—a primocane-fruiting genotype from the University of Arkansas breeding program. Cuttings were forced in a shallow bin containing a soilless potting medium. The average number of shoots per root cutting from 7.6 cm- and 15.2 cm- long root cuttings averaged 1.6 and 2.7 shoots per root cutting, respectively. Rooting percentage for collected shoots was nearly 100% regardless of root-cutting length source. A qualitative comparison of shoots from the two roots lengths was similar. The latter part of the study included various treatments on the rooted shoots that might affect the productivity and quality of the final product intended for nursery sales in early fall. With the aim of producing a flowering/fruiting shrub by late September, three treatments were applied: pot dimension, fertilizer rate, and shoot tipping. Fertilizer rate had the greatest impact of all treatments with the higher rate producing larger and more attractive plants. Above-normal summer/fall temperatures may explain lack of fruiting on APF-44 blackberries, but the dimension and size of some plants provided a portion of the intended aesthetic

Transposon and deletion mutagenesis of genes involved in perchlorate reduction in Azospira suillum PS.

UnlabelledAlthough much work on the biochemistry of the key enzymes of bacterial perchlorate reduction, chlorite dismutase, and perchlorate reductase has been published, understanding of the molecular mechanisms of this metabolism has been somewhat hampered by the lack of a clear model system amenable to genetic manipulation. Using transposon mutagenesis and clean deletions, genes important for perchlorate reduction in Azospira suillum PS have been identified both inside and outside the previously described perchlorate reduction genomic island (PRI). Transposon mutagenesis identified 18 insertions in 11 genes that completely abrogate growth via reduction of perchlorate but have no phenotype during denitrification. Of the mutants deficient in perchlorate reduction, 14 had insertions that were mapped to eight different genes within the PRI, highlighting its importance in this metabolism. To further explore the role of these genes, we also developed systems for constructing unmarked deletions and for complementing these deletions. Using these tools, every core gene in the PRI was systematically deleted; 8 of the 17 genes conserved in the PRI are essential for perchlorate respiration, including 3 genes that comprise a unique histidine kinase system. Interestingly, the other 9 genes in the PRI are not essential for perchlorate reduction and may thus have unknown functions during this metabolism. We present a model detailing our current understanding of perchlorate reduction that incorporates new concepts about this metabolism.ImportanceAlthough perchlorate is generated naturally in the environment, groundwater contamination is largely a result of industrial activity. Bacteria capable of respiring perchlorate and remediating contaminated water have been isolated, but relatively little is known about the biochemistry and genetics of this process. Here we used two complementary approaches to identify genes involved in perchlorate reduction. Most of these genes are located on a genomic island, which is potentially capable of moving between organisms. Some of the genes identified are known to be directly involved in the metabolism of perchlorate, but other new genes likely regulate the metabolism in response to environmental signals. This work has uncovered new questions about the regulation, energetics, and evolution of perchlorate reduction but also presents the tools to address them

Structure and evolution of chlorate reduction composite transposons.

UnlabelledThe genes for chlorate reduction in six bacterial strains were analyzed in order to gain insight into the metabolism. A newly isolated chlorate-reducing bacterium (Shewanella algae ACDC) and three previously isolated strains (Ideonella dechloratans, Pseudomonas sp. strain PK, and Dechloromarinus chlorophilus NSS) were genome sequenced and compared to published sequences (Alicycliphilus denitrificans BC plasmid pALIDE01 and Pseudomonas chloritidismutans AW-1). De novo assembly of genomes failed to join regions adjacent to genes involved in chlorate reduction, suggesting the presence of repeat regions. Using a bioinformatics approach and finishing PCRs to connect fragmented contigs, we discovered that chlorate reduction genes are flanked by insertion sequences, forming composite transposons in all four newly sequenced strains. These insertion sequences delineate regions with the potential to move horizontally and define a set of genes that may be important for chlorate reduction. In addition to core metabolic components, we have highlighted several such genes through comparative analysis and visualization. Phylogenetic analysis places chlorate reductase within a functionally diverse clade of type II dimethyl sulfoxide (DMSO) reductases, part of a larger family of enzymes with reactivity toward chlorate. Nucleotide-level forensics of regions surrounding chlorite dismutase (cld), as well as its phylogenetic clustering in a betaproteobacterial Cld clade, indicate that cld has been mobilized at least once from a perchlorate reducer to build chlorate respiration.ImportanceGenome sequencing has identified, for the first time, chlorate reduction composite transposons. These transposons are constructed with flanking insertion sequences that differ in type and orientation between organisms, indicating that this mobile element has formed multiple times and is important for dissemination. Apart from core metabolic enzymes, very little is known about the genetic factors involved in chlorate reduction. Comparative analysis has identified several genes that may also be important, but the relative absence of accessory genes suggests that this mobile metabolism relies on host systems for electron transport, regulation, and cofactor synthesis. Phylogenetic analysis of Cld and ClrA provides support for the hypothesis that chlorate reduction was built multiple times from type II dimethyl sulfoxide (DMSO) reductases and cld. In at least one case, cld has been coopted from a perchlorate reduction island for this purpose. This work is a significant step toward understanding the genetics and evolution of chlorate reduction

Disorders of Endocrine Function After Major Head Injury

This study was instigated after the diagnosis of post-traumatic hypopituitarism in a young female under our care, who had sustained a closed head injury in a motor cycle accident (Case 1, see below). A review of the world literature revealed only 47 reported cases of post-traumatic hypopituitarism, with the majority occurring in the last 20 years (Edwards and Clark, 1986). Surprisingly, we were able to collect a further 5 cases over a relatively short period of time, suggesting that it might be a more frequent complication than is currently recognised. It is of interest that the low prevalence of clinical hypopituitarism is in contrast to the frequent finding of damage to the hypothalamus and pituitary by pathologists after fatal head injury (Daniel, Prichard 6 Treip, 1959; Ceballos, 1966; Kornblum and Fisher, 1969; Treip, 1970; Crompton, 1971; Harper et al, 1986). As little endocrine information was available a large prospective study was undertaken to investigate abnormalities in endocrine function after head injury

Getting to know you: Accuracy and error in judgments of character

Character judgments play an important role in our everyday lives. However, decades of empirical research on trait attribution suggest that the cognitive processes that generate these judgments are prone to a number of biases and cognitive distortions. This gives rise to a skeptical worry about the epistemic foundations of everyday characterological beliefs that has deeply disturbing and alienating consequences. In this paper, I argue that this skeptical worry is misplaced: under the appropriate informational conditions, our everyday character-trait judgments are in fact quite trustworthy. I then propose a mindreading-based model of the socio-cognitive processes underlying trait attribution that explains both why these judgments are initially unreliable, and how they eventually become more accurate

Carrion Seeking in Brown Tree Snakes: Importance of Olfactory and Visual Cues

We performed field experiments to examine brown tree snake (Boiga irregularis) attraction to carrion. These snakes were attracted to carrion and entered traps baited with dead mice as readily as traps baited with live mice. Using the cues arising from both live and dead prey, we examined the relative importance of visual and chemical cues to brown tree snakes. With carrion lures, chemical cues alone were sufficient for attracting and capturing snakes, but with live prey lures visual cues were required to attract and capture brown tree snakes. Our study presents the first experimental field evidence showing carrion to be attractive to an ophidian predator and suggests that the relative importance of chemical and visual sensory stimuli to brown tree snakes is context-specific