Citrus Production, Constraints and Management Practices in Ethiopia: The Case of Pseudocercospora Leaf and Fruit Spot Disease

Citrus is economically important fruit crop in Ethiopia. However, its production is seriously constrained by various diseases including Pseudocercospora leaf and fruit spot. Surveys were conducted between June 2012 and May 2013 in the main citrus production areas of the country to assess the spread of the disease, and to determine its incidence and severity. A total of forty-nine citrus orchards in twenty-eight districts were surveyed. Random sampling techniques were used for data collection. The results showed that the disease had prevailed and widely spread in the districts assessed in the wet humid areas of the south, southwest, northwest, and north central parts, but not in the low altitude drier areas of the central rift valley and the eastern region of the country. Accordingly, 63.3% of the orchards surveyed were infected with the disease. The overall mean incidences of the disease on leaves of sweet orange, mandarin, lemon and lime were 36.2, 21.5, 17.1 and 16.3% while disease severity ratings were 2.6, 2.3, 2.0 and 1.7, respectively. Similarly, the average incidences and severities on fruits were 63.8, 29.4, 18.0 and 16.7%, and 4.0, 3.0, 2.0 and 2.0, in the same order. However, disease incidences in the different orchards ranged from zero to 76.7% on leaves and from zero to 100% on fruits. Disease severity ratings also varied from one to five on both leaves and fruits. In general, citrus orchards in the south and southwest Ethiopia that are known to have high rainfall and humidity conditions were more severely affected by the disease than those in the northwest and north central parts of the country. In these areas, respondents indicated that many farmers completely abandoned their citrus trees due to this disease. The causative agent was also identified to be the fungus Pseudocercospora angolensis based on cultural and morphological characteristics, and pathogenicity tests of representative isolates obtained from infected leaf and fruit samples.Keywords: Citrus Leaf and fruit spot disease; Pseudocercospora angolensis; Ethiopi

Effects of Salinity and Mycorrhizal Inoculation (Glomus fasciculatum) on Growth Responses of Grape Rootstocks (Vitis spp.)

A pilot experiment was conducted to determine the effects of soil salinity and inoculation with arbuscular mycorrhizalfungus (Glomus fasciculatum) on growth (shoot length, leaf number, internode length, and total dry weight), sporecount and root colonisation of grape rootstocks (Salt Creek, St. George, Dogridge and 1613). Analysis of varianceresults revealed that increasing salinity reduces growth, spore count and root colonisation, with St. George rootstockshowing the highest reduction. Although all rootstocks responded positively to mycorrhizal inoculation, the extentof host preference varied significantly. Dogridge was the least preferred, while the 1613 rootstock was the mostpreferred. The arbuscular fungal symbiosis increased vegetative growth, with 1613 attaining the highest growthunder saline conditions. All the inoculated rootstocks exhibited longer internodes, indicating the beneficial roleof mycorrhizal inoculation for improving plant growth and salt tolerance. Based on overall growth and total drymatter accumulation, the salt tolerance ranking of the four rootstocks, in decreasing order, was Dogridge, SaltCreek, 1613 and St. George

Genetic Assimilation and Canalisation in the Baldwin Effect

The Baldwin Effect indicates that individually learned behaviours acquired during an organism’s lifetime can influence the evolutionary path taken by a population, without any direct Lamarckian transfer of traits from phenotype to genotype. Several computational studies modelling this effect have included complications that restrict its applicability. Here we present a simplified model that is used to reveal the essential mechanisms and highlight several conceptual issues that have not been clearly defined in prior literature. In particular, we suggest that canalisation and genetic assimilation, often conflated in previous studies, are separate concepts and the former is actually not required for non-heritable phenotypic variation to guide genetic variation. Additionally, learning, often considered to be essential for the Baldwin Effect, can be replaced with a more general phenotypic plasticity model. These simplifications potentially permit the Baldwin Effect to operate in much more general circumstances

Glycogen Content Regulates Peroxisome Proliferator Activated Receptor-∂ (PPAR-∂) Activity in Rat Skeletal Muscle

Performing exercise in a glycogen depleted state increases skeletal muscle lipid utilization and the transcription of genes regulating mitochondrial β-oxidation. Potential candidates for glycogen-mediated metabolic adaptation are the peroxisome proliferator activated receptor (PPAR) coactivator-1α (PGC-1α) and the transcription factor/nuclear receptor PPAR-∂. It was therefore the aim of the present study to examine whether acute exercise with or without glycogen manipulation affects PGC-1α and PPAR-∂ function in rodent skeletal muscle. Twenty female Wistar rats were randomly assigned to 5 experimental groups (n = 4): control [CON]; normal glycogen control [NG-C]; normal glycogen exercise [NG-E]; low glycogen control [LG-C]; and low glycogen exercise [LG-E]). Gastrocnemius (GTN) muscles were collected immediately following exercise and analyzed for glycogen content, PPAR-∂ activity via chromatin immunoprecipitation (ChIP) assays, AMPK α1/α2 kinase activity, and the localization of AMPK and PGC-1α. Exercise reduced muscle glycogen by 47 and 75% relative to CON in the NG-E and LG-E groups, respectively. Exercise that started with low glycogen (LG-E) finished with higher AMPK-α2 activity (147%, p<0.05), nuclear AMPK-α2 and PGC-1α, but no difference in AMPK-α1 activity compared to CON. In addition, PPAR-∂ binding to the CPT1 promoter was significantly increased only in the LG-E group. Finally, cell reporter studies in contracting C2C12 myotubes indicated that PPAR-∂ activity following contraction is sensitive to glucose availability, providing mechanistic insight into the association between PPAR-∂ and glycogen content/substrate availability. The present study is the first to examine PPAR-∂ activity in skeletal muscle in response to an acute bout of endurance exercise. Our data would suggest that a factor associated with muscle contraction and/or glycogen depletion activates PPAR-∂ and initiates AMPK translocation in skeletal muscle in response to exercise

Seymour Aquifer Water Quality Improvement Project Final Report

The Seymour Aquifer is a shallow aquifer underlying over 300,000 acres in 20 counties in northwest central Texas. High nitrate concentrations are widespread in the Seymour Aquifer. Median nitrate levels in Knox, Haskell, Baylor, Hall, Wichita, Wilbarger, and Fisher counties exceeded the federal safe drinking water standard (10 mg/L NO3-N). This high concentration is a concern because although 90% of the water pumped from the aquifer is used for irrigation, it is also used as a municipal water source for the communities of Vernon, Burkburnett, and Electra and rural families in the region. To address this threat, the Texas State Soil and Water Conservation Board (TSSWCB), with 319(h) grant funding provided by the Environmental Protection Agency (EPA), worked cooperatively with the Haskell, Wichita-Brazos, and California Creek Soil and Water Conservation Districts (SWCDs); U.S. Department of Agriculture - Natural Resources Conservation Service (NRCS); Texas AgriLife Extension Service (AgriLife Extension); Texas A&M AgriLife – Texas Water Resources Institute (TWRI); Rolling Plains Groundwater Conservation District; and Texas AgriLife Research (AgriLife Research) to encourage the installation of subsurface drip irrigation (SDI) systems and other best management practices (BMPs) to improve water quality (i.e. reduce nitrate) and increase water quantity in the Seymour Aquifer. The project provided technical and financial assistance to producers to implement SDI and other BMPs, education programs and demonstrations of methods for reducing nitrate infiltration and improving irrigation efficiency and an evaluation of the effectiveness of SDI implementation. Considerable interest has been generated in SDI and other more efficient irrigation methods through the efforts of project partners. Through technical and financial assistance provided by the project through the TSSWCB and Haskell, Wichita-Brazos and California Creek SWCDs, 17 producers installed SDI systems on over 1,000 acres. In addition, irrigation management was implemented through the Water Quality Management Plans (WQMPs) developed on over 1,800 acres and nutrient management was implemented on over 2,500 acres. NRCS also began funding irrigation improvements in Haskell, Knox, Baylor, Wilbarger, Hardeman and Foard counties through the Seymour Aquifer Special Emphasis Area. Since this Special Emphasis Area was established in 2004, over $16 million dollars have been provided. In addition to implementing BMPs, a very important component of this project was conducting educational programs and demonstrations. Through seven programs conducted between 2005 and 2008, AgriLife Research and AgriLife Extension provided educational programs and demonstrations on nutrient management and irrigation management to 671 participants. The establishment of the permanent SDI demonstration site at the Chillicothe Station will ensure that these programs are sustained for many years to come and offer producers in the Texas Rolling Plains additional crop production options to enhance economic returns and water quality, and improve their quality of life

PRFdb: A database of computationally predicted eukaryotic programmed -1 ribosomal frameshift signals

The Programmed Ribosomal Frameshift Database (PRFdb) provides an interface to help researchers identify potential programmed -1 ribosomal frameshift (-1 PRF) signals in eukaryotic genes or sequences of interest. To identify putative -1 PRF signals, sequences are first imported from whole genomes or datasets, e.g. the yeast genome project and mammalian gene collection. They are then filtered through multiple algorithms to identify potential -1 PRF signals as defined by a heptameric slippery site followed by an mRNA pseudoknot. The significance of each candidate -1 PRF signal is evaluated by comparing the predicted thermodynamic stability (ΔG°) of the native mRNA sequence against a distribution of ΔG° values of a pool of randomized sequences derived from the original. The data have been compiled in a user-friendly, easily searchable relational database. The PRFdB enables members of the research community to determine whether genes that they are investigating contain potential -1 PRF signals, and can be used as a metasource of information for cross referencing with other databases. It is available on the web at http://dinmanlab.umd.edu/prfdb .https://doi.org/10.1186/1471-2164-9-33

PD-1 Blockade Modulates Functional Activities of Exhausted-Like T Cell in Patients With Cutaneous Leishmaniasis

Patients infected by Leishmania braziliensis develop debilitating skin lesions. The role of inhibitory checkpoint receptors (ICRs) that induce T cell exhaustion during this disease is not known. Transcriptional profiling identified increased expression of ICRs including PD-1, PDL-1, PDL-2, TIM-3, and CTLA-4 in skin lesions of patients that was confirmed by immunohistology where there was increased expression of PD-1, TIM-3, and CTLA-4 in both CD4^{+} and CD8^{+} T cell subsets. Moreover, PDL-1/PDL-2 ligands were increased on skin macrophages compared to healthy controls. The proportions PD1^{+}, but not TIM-3 or CTLA-4 expressing T cells in the circulation were positively correlated with those in the lesions of the same patients, suggesting that PD-1 may regulate T cell function equally in both compartments. Blocking PD-1 signaling in circulating T cells enhanced their proliferative capacity and IFN-γ production, but not TNF-α secretion in response to L. braziliensis recall antigen challenge in vitro. While we previously showed a significant correlation between the accumulation of senescent CD8^{+}CD45RA^{+}CD27^{-} T cells in the circulation and skin lesion size in the patients, there was no such correlation between the extent of PD-1 expression by circulating on T cells and the magnitude of skin lesions suggesting that exhausted-like T cells may not contribute to the cutaneous immunopathology. Nevertheless, we identified exhausted-like T cells in both skin lesions and in the blood. Targeting this population by PD-1 blockade may improve T cell function and thus accelerate parasite clearance that would reduce the cutaneous pathology in cutaneous leishmaniasis

Evolving Synaptic Plasticity with an Evolutionary Cellular Development Model

Since synaptic plasticity is regarded as a potential mechanism for memory formation and learning, there is growing interest in the study of its underlying mechanisms. Recently several evolutionary models of cellular development have been presented, but none have been shown to be able to evolve a range of biological synaptic plasticity regimes. In this paper we present a biologically plausible evolutionary cellular development model and test its ability to evolve different biological synaptic plasticity regimes. The core of the model is a genomic and proteomic regulation network which controls cells and their neurites in a 2D environment. The model has previously been shown to successfully evolve behaving organisms, enable gene related phenomena, and produce biological neural mechanisms such as temporal representations. Several experiments are described in which the model evolves different synaptic plasticity regimes using a direct fitness function. Other experiments examine the ability of the model to evolve simple plasticity regimes in a task -based fitness function environment. These results suggest that such evolutionary cellular development models have the potential to be used as a research tool for investigating the evolutionary aspects of synaptic plasticity and at the same time can serve as the basis for novel artificial computational systems

Endogenous ribosomal frameshift signals operate as mRNA destabilizing elements through at least two molecular pathways in yeast

Although first discovered in viruses, previous studies have identified operational −1 ribosomal frameshifting (−1 RF) signals in eukaryotic genomic sequences, and suggested a role in mRNA stability. Here, four yeast −1 RF signals are shown to promote significant mRNA destabilization through the nonsense mediated mRNA decay pathway (NMD), and genetic evidence is presented suggesting that they may also operate through the no-go decay pathway (NGD) as well. Yeast EST2 mRNA is highly unstable and contains up to five −1 RF signals. Ablation of the −1 RF signals or of NMD stabilizes this mRNA, and changes in −1 RF efficiency have opposing effects on the steady-state abundance of the EST2 mRNA. These results demonstrate that endogenous −1 RF signals function as mRNA destabilizing elements through at least two molecular pathways in yeast. Consistent with current evolutionary theory, phylogenetic analyses suggest that −1 RF signals are rapidly evolving cis-acting regulatory elements. Identification of high confidence −1 RF signals in ∼10% of genes in all eukaryotic genomes surveyed suggests that −1 RF is a broadly used post-transcriptional regulator of gene expression