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Chemical control of the red palm weevil Rhynchophorus ferrugineus and the castniid palm borer Paysandisia archon
Get PDFThe chemical control of R. ferrugineus and P. archon is constraint due to the biology of the target pests, that spend most of their life cycles tunneling the palms, and to the limited amount of active substances available. Although several application methods have been designed to target immature stages of both pests when protected in the palm tissues (as drench and injection), further research is needed to identify new selective molecules and delivery methods. Nowadays, chemical control has to be carefully combined with other more sustainable methods to prevent the appearance of resistance and other undesirable sideeffects of pesticide use. In this short revision, we will discuss different application methods that, contrary to other control methods, can be used as curative tools. Such a precious use of these biocides makes critical to raise awareness among stakeholders about the
importance of proper insecticide use to ensure their sustainability
A super-family of transcriptional activators regulates bacteriophage packaging and lysis in Gram-positive bacteria
Get PDFThe propagation of bacteriophages and other mobile genetic elements requires exploitation of the phage mechanisms involved in virion assembly and DNA packaging. Here, we identified and characterized four different families of phage-encoded proteins that function as activators required for transcription of the late operons (morphogenetic and lysis genes) in a large group of phages infecting Gram-positive bacteria. These regulators constitute a super-family of proteins, here named late transcriptional regulators (Ltr), which share common structural, biochemical and functional characteristics and are unique to this group of phages. They are all small basic proteins, encoded by genes present at the end of the early gene cluster in their respective phage genomes and expressed under cI repressor control. To control expression of the late operon, the Ltr proteins bind to a DNA repeat region situated upstream of the terS gene, activating its transcription. This involves the C-terminal part of the Ltr proteins, which control specificity for the DNA repeat region. Finally, we show that the Ltr proteins are the only phage-encoded proteins required for the activation of the packaging and lysis modules. In summary, we provide evidence that phage packaging and lysis is a conserved mechanism in Siphoviridae infecting a wide variety of Gram-positive bacteria
Genetic variability and evolutionary dynamics of viruses of the family Closteroviridae.
Get PDFRNA viruses have a great potential for genetic variation, rapid evolution and adaptation. Characterization of the genetic variation of viral populations provides relevant information on the processes involved in virus evolution and epidemiology and it is crucial for designing reliable diagnostic tools and developing efficient and durable disease control strategies. Here we performed an updated analysis of sequences available in Genbank and reviewed present knowledge on the genetic variability and evolutionary processes of viruses of the family Closteroviridae. Several factors have shaped the genetic structure and diversity of closteroviruses. (I) A strong negative selection seems to be responsible for the high genetic stability in space and time for some viruses. (2) Long distance migration, probably by human transport of infected propagative plant material, have caused that genetically similar virus isolates are found in distant geographical regions. (3) Recombination between divergent sequence variants have generated new genotypes and plays an important role for the evolution of some viruses of the family Closteroviridae. (4) Interaction between virus strains or between different viruses in mixed infections may alter accumulation of certain strains. (5) Host change or virus transmission by insect vectors induced changes in the viral population structure due to positive selection of sequence variants with higher fitness for host-virus or vector-virus interaction (adaptation) or by genetic drift due to random selection of sequence variants during the population bottleneck associated to the transmission process
Citrus tristeza virus p23: Determinants for Nucleolar Localization and Their Influence on Suppression of RNA Silencing and Pathogenesis
No full textCitrus tristeza virus (CTV) encodes a singular protein (p23, 209 amino acids) with multiple functions, including RNA silencing suppression (RSS). Confocal laser-scanning microscopy of green fluorescent protein (GFP)-p23 agroexpressed in Nicotiana benthamiana revealed its accumulation in the nucleolus, Cajal bodies, and plasmodesmata. To dissect the nudeolar localization signal (NoLS) typically associated with basic motifs, seven truncated and 10 point-mutated versions of p23 were assayed. Deletion mutants showed that regions 50 to 86 and 100 to 157 (excluding fragment 106 to 114), both with basic motifs and the first with a zinc-finger, contain the (bipartite) NoLS. Alanine substitutions delimited this signal to three cysteines of the Zn-finger and some basic amino acids. RSS activity of p23 in N. benthamiana was abolished by essentially all mutants, indicating that it involves most p23 regions. The necrotic-inducing ability of p23 when launched in N. benthamiana from Potato virus X was only retained by deletion mutant 158-209 and one substitution mutant, showing that the Zn-finger and flanking basic motifs form part of the pathogenic determinant. Ectopic expression of p23 and some deletion mutants in transgenic Mexican lime demarcated a similar determinant, suggesting that p23 affects related pathways in citrus and N. benthamiana. Both RSS activity and pathogenicity of p23 appear related to its nucleolar localization
Assignment of SNP allelic configuration in polyploids using competitive allele-specific PCR: application to citrus triploid progeny
No full textPolyploidy is a major component of eukaryote evolution. Estimation of allele copy numbers for molecular markers has long been considered a challenge for polyploid species, while this process is essential for most genetic research. With the increasing availability and whole-genome coverage of single nucleotide polymorphism (SNP) markers, it is essential to implement a versatile SNP genotyping method to assign allelic configuration efficiently in polyploids. This work evaluates the usefulness of the KASPar method, based on competitive allele-specific PCR, for the assignment of SNP allelic configuration. Citrus was chosen as a model because of its economic importance, the ongoing worldwide polyploidy manipulation projects for cultivar and rootstock breeding, and the increasing availability of SNP markers. Fifteen SNP markers were successfully designed that produced clear allele signals that were in agreement with previous genotyping results at the diploid level. The analysis of DNA mixes between two haploid lines (Clementine and pummelo) at 13 different ratios revealed a very high correlation (average 09796; s.d. 00094) between the allele ratio and two parameters [THETA angle tan(1) (y/x) and y y/(x y)] derived from the two normalized allele signals (x and y) provided by KASPar. Separated cluster analysis and analysis of variance (ANOVA) from mixed DNA simulating triploid and tetraploid hybrids provided 9971 correct allelic configuration. Moreover, triploid populations arising from 2n gametes and interploid crosses were easily genotyped and provided useful genetic information. This work demonstrates that the KASPar SNP genotyping technique is an efficient way to assign heterozygous allelic configurations within polyploid populations. This method is accurate, simple and cost-effective. Moreover, it may be useful for quantitative studies, such as relative allele-specific expression analysis and bulk segregant analysis
Cytological and molecular characterization of three gametoclones of Citrus clementina
Get PDFBackground: Three gametoclonal plants of Citrus clementina Hort. ex Tan., cv. Nules, designated ESP, FRA, and ITA (derived from three labs in Spain, France, and Italy, respectively), were selected for cytological and molecular characterization in order to elucidate genomic rearrangements provoked by haploidization. The study included comparisons of their ploidy, homozygosity, genome integrity, and gene dosage, using chromosome counting, flow cytometry, SSR marker genotyping, and array-Comparative Genomic Hybridization (array-CGH). Results: Chromosome counting and flow cytometry revealed that ESP and FRA were haploid, but ITA was tri-haploid. Homozygous patterns, represented by a single peak (allele), were observed among the three plants at almost all SSR loci distributed across the entire diploid donor genome. Those few loci with extra peaks visualized as output from automated sequencing runs, generally low or ambiguous, might result from amplicons of paralogous members at the locus, non-specific sites, or unexpected recombinant alleles. No new alleles were found, suggesting the genomes remained stable and intact during gametogenesis and regeneration. The integrity of the haploid genome also was supported by array-CGH studies, in which genomic profiles were comparable to the diploid control. Conclusions: The presence of few gene hybridization abnormalities, corroborated by gene dosage measurements, were hypothetically due to the segregation of hemizygous alleles and minor genomic rearrangements occurring during the haploidization procedure. In conclusion, these plants that are valuable genetic and breeding materials contain completely homozygous and essentially intact genomes
Efecto de la immunocastración y de la castración quirúrgica sobre los rendimientos productivos y la calidad de la canal en cerdas Ibéricas de cebo
Get PDFSe utilizaron 192 cerdas Ibéricas (Duroc x Ibérica) con 110 días de vida y 44,94 ± 3,41 kg de peso, para
probar el efecto de la castración inmunológica con Improvac® (Pfizer Animal Health). El ensayo se llevó
a cabo en el Centro de Pruebas de Porcino del Instituto Tecnológico Agrario de Castilla y León (Itacyl, Consejería de Agricultura y Ganadería). El experimento se diseñó en bloques al azar, con 3 tratamientos (cerdas castradas quirúrgicamente, enteras e inmunocastradas), 48 réplicas totales de 4 cerdas cada una y 16 réplicas por tratamiento. Los animales se pesaron individualmente cada 15 días y se calculó el consumo de pienso, la ganancia de peso y el índice de conversión. Una vez aplicadas las dos dosis de Improvac® (a las 18 y 22 semanas de edad -60 kg y 84,2 kg de peso, respectivamente-) las diferencias de peso vivo entre enteras e inmunocastradas se volvieron estadísticamente significativas (P < 0,05) por encima de los
100 kg, permaneciendo la significación hasta los 170 kg, y presentando éstas últimas mayor consumo,
ganancia media diaria e índice de conversión (21,25, 19,24 y 1,44%, respectivamente; P < 0,05). En relación con las castradas y tras la aplicación de la 2ª dosis, las inmunocastradas aumentaron el consumo (12% de media, en función del peso vivo considerado) y la ganancia diaria (22,24%), disminuyendo la conversión un 7,6% (P < 0,05). Por otra parte, las castradas consumieron más (8,35%), con menor ganancia diaria (2,6%) y una mayor conversión (11%) que las enteras (P < 0,05). Un primer lote de 96 cerdas fue enviado a matadero a los 8,2 meses de edad, con pesos de 162,88 kg (castradas), 164,52 kg (enteras) y 170,76 kg
(inmunocastradas). Para las cerdas de este lote, el rendimiento de la canal fue de 78,02 vs 79,14 y 78,79%, para enteras, castradas e inmunocastradas respectivamente (P < 0,05), mientras que el peso de piezas nobles fue mayor en las enteras e inmunocastradas (P < 0,05). En las condiciones de nuestro trabajo, podemos concluir que Ia inmunocastración es una alternativa productiva ventajosa a la castración física en cerdas Ibéricas, recomendándose una separación de 10 ± 2 semanas entre la aplicación de la 2ª dosis de
Improvac® y el sacrificio para la obtención del máximo beneficio, e igualmente, con las mismas pautas de aplicación, presenta una conversión más favorable a los distintos pesos de sacrificio comerciales en relación con cerdas enteras. La castración quirúrgica es la opción menos interesante
Carbon balance of citrus plantations in Eastern Spain
No full textGlobal warming due to the continuous rise in CO2 emissions has been documented in the last few decades. This work is a first effort to estimate the net carbon incorporation in citrus plantations cultivated under typical land use. The approach involves a biomass-based study of carbon accumulation and a complementary analysis of the associated CO2 fluxes. The total C content allocated to trees aged 2-14 years was determined through the direct and destructive harvesting of all tree organs. A stable pattern of biomass production in tree components was observed in plants 12 years old and older and was responsible for the sequestration of more than 50 kg C tree(-1). Annual C fixation in fruit and new vegetative flushes accounted for up to approximately 75% of the total amount sequestered per year, whereas the contribution of the old, permanent organs (branches', trunk, and tap-coarse roots) was minor (approximately 25%). Further experiments were conducted on adult 12-year-old trees to confirm the data and determine the particular contribution of CO2 fluxes from tree organs and soil to the final values. Data revealed that leaves were responsible for a total net C fixation of 15.4 Mg C ha(-1) yr(-1) (higher than 55% of the total C fixed). The complementary, regular monitoring of fruit respiration rates showed that fruit respiration played only a minor role, responsible for the emission of 2.3 Mg C ha(-1) yr(-1). Minimum losses were also found when soil respiration rates were investigated, accounting for a total annual C loss of 2.7 Mg C ha(-1) yr(-1). Taken together, these results indicate that our plantation was responsible for a net C fixation of close to 10 Mg C ha(-1) yr(-1). Assimilatory processes in leaves accounted for the highest proportion of C allocated to the tree, while losses due to leaf and fruit respiration were of minor importance. Under typical culture conditions (drip irrigation and absence of ground cover), soil respiration rates accounted for a low level of C loss to the atmosphere. Because citrus is the second largest fruit crop cultivated in the EU, such data are very relevant to the mitigation of climate change. (C) 2013 Elsevier B.V. All rights reserved
Complete sequence of Erwinia piriflorinigrans plasmids pEPIR37 and pEPIR5 and role of pEPIR37 in pathogen virulence
No full textErwinia piriflorinigrans is a newly described pathogen causing necrosis of pear blossoms. Complete sequencing of the 37-kb plasmid pEPIR37 common to 27 E.piriflorinigrans strains revealed homology to sequences of the ubiquitous plasmids pEA29 of the fire blight pathogen E.amylovora, plasmid pEP36 of E.pyrifoliae, plasmid pEJ30 of Erwinia sp. from Japan, and genomic regions of the related Rosaceae epiphytic Erwinia species E.tasmaniensis and E.billingiae. A second 5.5-kb cryptic plasmid pEPIR5, found in 12 E.piriflorinigrans strains, was also sequenced revealing mobilization and replication proteins with similarities to many small ColE1-type plasmids in Erwinia spp. and other enterobacteria. Functional analyses of pEPIR37 introduced into a strain of E.amylovora cured of pEA29 plasmid, which has a reduced virulence, showed a role in increasing symptom development similar to that observed in E.amylovora carrying plasmid pEA29
