Integración de la Bioinformática en la investigación molecular en especies forestales: el caso de la encina (Quercus ilex)

The term Bioinformatics, first coined by Paulien Hogeweg and Ben Hesper, back in 1970 to describe ’the study of informatic processes in biotic systems’, can be defined as “research, development, or application of computational tools and approaches for expanding the use of biological, medical, behavioural or health data, including those to acquire, represent, describe, store, analyze, or visualize such data” or “the development and application of data-analytical and theoretical methods, mathematical modelling, and computational simulation techniques to the study of biological, behavioural, and social systems”. The first definition deals with the biological information management, and the second one with computational biology. The general objective and methodology employed in the current Thesis, “Integration of Bioinformatics to molecular research in forest species: the case of Holm oak (Quercus ilex)”, is focused on the first definition. The use of bioinformatic tools (algorithms, programs, databases and repositories) has been used to construct the transcriptome, proteome and metabolome of Holm oak and their integration to define the metabolism and responses to drought in this species. Since the end of the last century, biological research has moved from a reductionist to holistic paradigm, which have been possible thanks to the great technological advances, especially in the molecular biology discipline. Thus, the appearance of platforms based on the Next Generation Sequencing (NGS), and transcriptomics, and Mass Spectrometry(MS),for proteomics and metabolomics has made possible to obtain from hundreds to thousands of data in a single experiment, being impossible the management and analysis of them without the employment of informatics tools. The employment of high throughput techniques and their combination with classic approaches is what defines“SystemsBiology”. It do not only analyse thousands and thousands of molecular entities of an individual, but also the integration and creation of predictive models. This is quite feasible with model organisms (e.g. Arabidopsis), but it is a real challenge for those orphan and recalcitrant experimental systems such as Q. ilex. The study of this species is justified because of the environmental and economic importance in Spain and, because it faces a problem of increasing tree mortality associated to the decline syndrome, a situation that can be worsen in a climate change scenario. Biotechnology can contribute to solve this problem through breeding programs based on markers-assisted selection of elite genotypes that are more tolerant and resistant to biotic and abiotic stresses and more resilient to climate change. As a continuation of the work carried out since 2004 by the research group “Agroforestry and Plant Biochemistry, Proteomics, and Systems Biology”, mostly based on classic biochemistry, physiology and proteomics, and considering that neither the genome of Holm oak has been sequenced yet nor DNA or proteins sequences are available in public databases, as first objective of the Thesis was proposed the construction of the first reference transcriptome for this species. The work is presented in chapter 3, and has been published in Frontiers in Molecular Bioscience. For that purpose, the mRNA extracted from homogenized tissue from acorn embryo, leaves, and roots, was sequenced using an Illumina Hiseq 2500 platform. Three different assemblers were employed, TRINITY, RAY, and MIRA. The assemblies obtained were aligned against the most accurate and nearest phylogenetically transcriptome currently available, that of Quercus robur and Quercus petraea. MIRA generated more and longer contigs than RAY and TRINITY (MIRA>RAY>TRINITY). So, MIRA assembly was used to continue with the corresponding annotation of Q. ilex transcriptome, resulting in 31973 annotated sequences were obtained by Blast2GO using Swiss-Prot as reference database. As a continuation of the previous work, and as a second objective, a new sequencing platform, Ion Torrent, was evaluated in the construction and analysis of the Q. ilex transcriptome. The obtained results are presented in chapter 4 and have been already published in PLoS ONE. Raw sequence reads, obtained from Illumina and Ion Torrent, were assembled by three different software, MIRA, RAY and TRINITY. A hybrid transcriptome combining reads from both sequencing technologies was also assembled using RAY. The hybrid assembly generated the most complete transcriptome. The assembly of Ion Torrent reads of MIRA showed the highest number of shared sequences (84.8%) with the oak transcriptome. In addition, an in silico proteomic analysis was carried out using the translated assemblies as databases. Those from Ion Torrent showed more proteins compared to the Illumina and hybrid assemblies. All the assembled transcripts from the hybrid transcriptome were annotated and grouped according to the corresponding biological processes, molecular functions and cellular components (Gene Ontology). This new generated transcriptome represents a valuable tool to conduct differential gene expression studies in response to biotic and abiotic stresses and to assist and validate the ongoing Q. ilex whole genome sequencing. By using the above mentioned plant sample, the transcriptomic (NGS-Illumina), proteomic (shotgun LC-MS/MS, Orbitrap), and metabolomic (GCMS) profiles were analysed. Results are presented in chapter 5, and have been already published in Frontiers in Plant Science. The annotated Q. ilex transcriptome was compared against the complete in silico proteomes of Arabidopsis thaliana (UP0000065489, Oryza sativa subsp. Japonica (UP00005968010), Populus trichocarpa (UP00000672911), and Eucaliptus grandis (UP00003071112) in order to elucidate the unique and shared sequences. Also, the EC numbers of each proteome were contrasted to achieve a complete picture of the metabolic pathways coverage differences among proteomes studied in previously mentioned species. The descriptive analysis and the visualization of data on a gene-by-gene basis on schematic diagrams (maps) of the biological processes described in Mapman, resulted in the identification of around 62629 transcripts, 2380 protein species, and 62 metabolites. Data were compared with those reported for model plant species, whose genome has been sequenced and well annotated, including Arabidopsis, japonica rice, poplar, and eucalyptus. The integration of the large amount of data reported using bioinformatics tools allowed the Holm oak metabolic network to be partially reconstructed. From the 127 metabolic pathways reported in KEGG pathway database, 123 metabolic pathways can be visualized when using the described methodology. They included: carbohydrate and energy metabolism, amino acid metabolism, lipid metabolism, nucleotide metabolism, and biosynthesis of secondary metabolites. The TCA cycle was the pathway most represented with 5 out of 10 metabolites, 6 out of 8 protein enzymes, and 8 out of 8 enzyme transcripts. On the other hand, gaps, missed pathways, included metabolism of terpenoids and polyketides and lipid metabolism. The multi-omics resource generated in this work will set the basis for ongoing and future studies, bringing the Holm oak closer to model species. As a final objective of the current Thesis, an integrated transcriptomics and proteomics analysis of the response to drought in Q. ilex seedlings has been carried out. Seedlings were subjected to drought conditions by water withholding, and leaf tissue sampled at two times of the experiment, 20 and 25 days. RNA and proteins were extracted and analysed by using RNA-seq (Illumina), and proteomics, LC-MS/MS Orbitrap. Data are presented in chapter 6; it also corresponds to a manuscript to be submitted for publication. Gene products were identified and quantified at transcript and protein levels, establishing correlations between transcript and the corresponding protein abundance. Gene ontology (GO) analysis was performed to classify identified transcripts and proteins in terms of biological process, molecular function and cellular component. A multivariate analysis of the total and variable datasets at transcript and protein levels was performed with mixOmics. To acquire an integrated visualization of Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway maps, total transcript and protein datasets, specifying those variable transcripts and proteins, were analysed by Paintomics 3 (v0.4.5), considering Arabidopsis thaliana as a model reference. Pathways with p-value RAY>Trinity). Por lo tanto, las secuencias ensambladas con MIRA fueron las que se usaron para continuar con la anotación correspondiente del transcriptoma Q. ilex, lo que resultó en 31973 secuencias anotadas obtenidas por Blast2GO utilizando Swiss-Prot como base de datos de referencia. Como continuación del trabajo descrito en el capítulo 4, y como segundo objetivo, se evaluó una nueva plataforma de secuenciación, Ion Torrent, para la construcción y análisis del transcriptoma de Q. ilex. Los resultados obtenidos han sido publicados en PLoS ONE. Como en el capítulo anterior, las lecturas obtenidas a partir de Illumina y Ion Torrent se ensamblaron utilizando tres programas diferentes, MIRA, RAY y TRINITY. En el ensamblado de MIRA con Illumina y el de TRINITY con Ion Torrent generaron el mayor número de transcritos anotados (62628 y 74058 respectivamente). El ensamblado de MIRA con Ion Torrent generó el mayor número de secuencias compartidas con el transcriptoma del roble (84.8%). RAY generó los mejores resultados atendiendo al número de contigs y longitud de los mismos, con valores de E90N50 de 1122bp. Todos los transcritos del nuevo transcriptoma de referencia fueron anotados y agrupados en términos de Gene Ontology ("Biological Process", "Celullar Component" y "Molecular Function"). Dicho transcriptoma se tradujo in silico, obteniéndose una base de datos de proteínas que será utilizada en experimentos de proteómica para la identificación de productos génicos. El uso de dicha base de datos incrementó notablemente el número de especies proteicas identificadas y los parámetros de confianza de la identificación. A partir de las bases de datos generadas y los datos multiómicos obtenidos cuando se utilizó una muestra de encina consistente en un pool de extractos de diferentes tejidos (embrión, hoja y raíz) se reconstruyeron diferentes rutas metabólicas tal y como ocurren en Q. ilex. Los resultados se presentan en el capítulo 5 y han sido publicados en Frontiers in Plant Science. Se llevó a cabo la extracción independiente a partir de la misma muestra del RNA, proteínas y metabolitos, estableciéndose el perfil ómico mediante NGS-Illumina (RNA), shotgun LC-MS/MS, Orbitrap (proteínas) y GC-MS (metabolitos). Se identificaron 62629 transcritos, 2380 especies proteicas y 62 metabolitos. Se llevó a cabo la identificación de productos génicos correspondientes a enzimas mediante la comparación con genomas de referencia incluyendo Arabidopsis thaliana (UP0000065489, Oryza sativa subsp. japonica (UP00005968010), Populus trichocarpa (UP00000672911), and Eucaliptus grandis (UP00003071112). Delas127rutasmetabólicasdescritasenKEGG, y mediante el empleo de Mapman, se visualizaron 123, entre ellas, las del metabolismo energético, de carbohidratos, de aminoacidos, lípicos, nucleótidos y secundario. El ciclo de los ácidos tricarboxílicos (TCA) fue la ruta mejor representadas con 5 de 10 metabolitos, 6 de 8 proteínas enzimáticas y 8 de 8 transcritos. Por otro lado, hay rutas que no se observaron o estaban muy poco representadas, como por ejemplo las del metabolismo de lípidos, terpenoides y policétidos. Como objetivo final de la presente tesis, se llevó a cabo un análisis transcriptómico y proteómico integrado de la respuesta a sequía en plantones de Q. ilex. Los resultados se presentan en el capítulo 6, correspondiente a un manuscrito que será enviado para su publicación. Las plántulas de Q. ilex crecieron en macetas con perlita, siendo sometidas a condiciones de sequía por falta de riego durante 30 días. Se tomaron muestras de hojas a dos tiempos, cuando la fluorescencia de las hojas disminuyó en un 30% y un 50% (20 y 25 días). Tras la extracción de RNA y proteínas se llevó a cabo su análisis mediante RNA-Seq (Illumina) y proteómica “shotgun” (LS-MS/MS, Orbitrap). El análisis de RNA-seq generó 47868 transcritos correspondientes a 21000 unigenes, con 3588 diferencias cualitativas o cuantitativas entre plántulas irrigadas y no irrigadas (1149 sobreexpresados y 2439 reprimidos). A partir de la proteómica “shotgun” se identificaron 4008 proteoformas, productos de 2767 genes diferentes; de ellos, 640 presentaron diferencias cualitativas o cuantitativas en abundancia entre tratamientos (353 más y 287 menos abundantes en condiciones de sequía). Los productos genéticos variables se clasificaron en términos de Gene Ontology (proceso biológico, función molecular y componente celular) y en rutas metabólicas de KEGG en el caso de las enzimas. El conjunto de datos variables se sometió a análisis estadístico multivariante, PCA y sPLS. Finalmente, se usó GeneMANIA para la construcción de redes de interacción. Hubo cambios importantes en el patrón de expresión génica siendo los grupos de respuesta a estrés y cloroplastos lo más afectados. Respecto a rutas metabólicas, se detectaron cambios en la síntesis de proteínas, fotosíntesis, carbohidratos, aminoácidos y fenólicos. Hubo cambios transitorios (observado a un solo tiempo) o permanentes (comunes a los dos tiempos) detectados a nivel de transcrito y/o proteína. El número de productos génicos variables detectados por ambas plataformas fue mínimo, entre ellos RPS2, 4CL2, PSB28 y RIN4. A partir del conjunto de datos de transcritos y proteínas variables, se construyeron dos redes de interacción: la primera incluía los genes sobreexpresados CLPB2, CLPB3, HSP70, HSP17.4, FtsH6, AT1G23740, SMT1 y UGP3, y los genes reprimidos ABA2, RPS1, ADK y RPL4, y la segunda red incluía los genes sobreexpresados CLPB2, CLPB3, HSP70, HSP17.4, FtsH6, AT1G23740, AP1, INVE, AT4G2740, CAD4, FEN1 y HIPP27 y el gen reprimido ABA2. Se proponen como genes marcadores de respuesta y tolerancia a sequía en encina a aquellos sobreexpresados a los dos tiempos y detectados a nivel de transcrito y proteína. Solo un número de genes cumplen dichas características entre los que se incluyen posibles proteínas de respuest

Ecología, construcción e innovación: Una alerta al cambio

The environmental damage caused to the planet is largely due to the pollution left behind by the misuse of debris, a large ecological footprint, the deforestation of important spaces due to the need to build, and bad practices within civil engineering. It is known that this problem is worldwide, but the most appropriate in our context and analysis is to focus on Colombia. A secondary objective of this article is to raise awareness and provide possible solutions to a problem as extensive and complicated as pollution. At the end of reading the article, it will be shown that this problem does not only affect a few people but the country in general.El daño ambiental provocado al planeta se produce en gran medida por la contaminación que deja la mala utilización de escombros, una gran huella ecológica, la deforestación de espacios importantes por la necesidad de construir, y las malas prácticas dentro de la ingeniería civil. Se sabe que esta problemática es a nivel mundial, pero lo más adecuado en nuestro contexto y análisis es centrarse en Colombia. Un objetivo secundario de este artículo es la concientización, y dar unas posibles soluciones a un problema tan extenso y tan complicado como lo es la contaminación. Al finalizar de leer el artículo se mostrará que esta problemática no afecta solo a unos cuantos sino al país en general

A Multi-Omics Analysis Pipeline for the Metabolic Pathway Reconstruction in the Orphan Species Quercus ilex

Holm oak (Quercus ilex) is the most important and representative species of the Mediterranean forest and of the Spanish agrosilvo-pastoral “dehesa” ecosystem. Despite its environmental and economic interest, Holm oak is an orphan species whose biology is very little known, especially at the molecular level. In order to increase the knowledge on the chemical composition and metabolism of this tree species, the employment of a holistic and multi-omics approach, in the Systems Biology direction would be necessary. However, for orphan and recalcitrant plant species, specific analytical and bioinformatics tools have to be developed in order to obtain adequate quality and data-density before to coping with the study of its biology. By using a plant sample consisting of a pool generated by mixing equal amounts of homogenized tissue from acorn embryo, leaves, and roots, protocols for transcriptome (NGS-Illumina), proteome (shotgun LC-MS/MS), and metabolome (GC-MS) studies have been optimized. These analyses resulted in the identification of around 62629 transcripts, 2380 protein species, and 62 metabolites. Data are compared with those reported for model plant species, whose genome has been sequenced and is well annotated, including Arabidopsis, japonica rice, poplar, and eucalyptus. RNA and protein sequencing favored each other, increasing the number and confidence of the proteins identified and correcting erroneous RNA sequences. The integration of the large amount of data reported using bioinformatics tools allows the Holm oak metabolic network to be partially reconstructed: from the 127 metabolic pathways reported in KEGG pathway database, 123 metabolic pathways can be visualized when using the described methodology. They included: carbohydrate and energy metabolism, amino acid metabolism, lipid metabolism, nucleotide metabolism, and biosynthesis of secondary metabolites. The TCA cycle was the pathway most represented with 5 out of 10 metabolites, 6 out of 8 protein enzymes, and 8 out of 8 enzyme transcripts. On the other hand, gaps, missed pathways, included metabolism of terpenoids and polyketides and lipid metabolism. The multi-omics resource generated in this work will set the basis for ongoing and future studies, bringing the Holm oak closer to model species, to obtain a better understanding of the molecular mechanisms underlying phenotypes of interest (productive, tolerant to environmental cues, nutraceutical value) and to select elite genotypes to be used in restoration and reforestation programs, especially in a future climate change scenario

Responses and Differences in Tolerance to Water Shortage under Climatic Dryness Conditions in Seedlings from Quercus spp. and Andalusian Q. ilex Populations

Analyzing differences in tolerance to drought in Quercus spp., and the characterization of these responses at the species and individual population level, are imperative for the selection of resilient elite genotypes in reforestation programs. The main objective of this work was to evaluate differences in the response and tolerance to water shortage under in five Quercus spp. and five Andalusian Q. ilex populations at the inter- and intraspecies level. Six-month-old seedlings grown in perlite were subjected to drought treatments by withholding water for 28 days under mean 37 °C temperature, 28 W m-2 solar irradiance, and 41% humidity. The use of perlite as the substrate enabled the establishment of severe drought stress with reduction in water availability from 73% (field capacity) to 28% (dryness), corresponding to matric potentials of 0 and −30 kPa. Damage symptoms, mortality rate, leaf water content, photosynthetic, and biochemical parameters (amino acids, sugars, phenolics, and pigments) were determined. At the phenotypic level, based on damage symptoms and mortality, Q. ilex behaved as the most drought tolerant species. Drought caused a significant decrease in leaf fluorescence, photosynthesis rate, and stomatal conductance in all Quercus spp. analyzed, being less pronounced in Q. ilex. There were not differences between irrigated and non-irrigated Q. ilex seedlings in the content of sugar and photosynthetic pigments, while the total amino acid and phenolic content significantly increased under drought conditions. As a response to drought, living Q. ilex seedlings adjust stomata opening and gas exchange, and keep hydrated, photosynthetically active, and metabolically competent. At the population level, based on damage symptoms, mortality, and physiological parameters, the eastern Andalusian populations were more tolerant than the western ones. These observations inform the basis for the selection of resilient genotypes to be used in breeding and reforestation programs

Proteomics Data Analysis for the Identification of Proteins and Derived Proteotypic Peptides of Potential Use as Putative Drought Tolerance Markers for Quercus ilex

Drought is one of the main causes of mortality in holm oak (Quercus ilex) seedlings used in reforestation programs. Although this species shows high adaptability to the extreme climate conditions prevailing in Southern Spain, its intrinsic genetic variability may play a role in the differential response of some populations and individuals. The aim of this work was to identify proteins and derived proteotypic peptides potentially useful as putative markers for drought tolerance in holm oak by using a targeted post-acquisition proteomics approach. For this purpose, we used a set of proteins identified by shotgun (LC-MSMS) analysis in a drought experiment on Q. ilex seedlings from four different provenances (viz. the Andalusian provinces Granada, Huelva, Cadiz and Seville). A double strategy involving the quantification of proteins and target peptides by shotgun analysis and post-acquisition data analysis based on proteotypic peptides was used. To this end, an initial list of proteotypic peptides from proteins highly represented under drought conditions was compiled that was used in combination with the raw files from the shotgun experiment to quantify the relative abundance of the fragment’s ion peaks with the software Skyline. The most abundant peptides under drought conditions in at least two populations were selected as putative markers of drought tolerance. A total of 30 proteins and 46 derived peptides belonging to the redox, stress-related, synthesis,-folding and degradation, and primary and secondary metabolism functional groups were thus identified. Two proteins (viz., subtilisin and chaperone GrpE protein) were found at increased levels in three populations, which make them especially interesting for validation drought tolerance markers in subsequent experiments.Fil: San Eufrasio, Bonoso. Universidad de Córdoba; EspañaFil: Bigatton, Ezequiel Darío. Universidad de Córdoba; España. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias. Departamento de Recursos Naturales. Cátedra de Microbiología Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Guerrero Sánchez, Victor M.. Universidad de Córdoba; EspañaFil: Chaturvedi, Palak. Vienna University of Technology; AustriaFil: Jorrín Novo, Jesús V.. Universidad de Córdoba; EspañaFil: Rey, María Dolores. Universidad de Córdoba; EspañaFil: Castillejo Sánchez, María Ángeles. Universidad de Córdoba; Españ

Ion Torrent and lllumina, two complementary RNA-seq platforms for constructing the holm oak (Quercus ilex) transcriptome

Transcriptome analysis is widely used in plant biology research to explore gene expression across a large variety of biological contexts such as those related to environmental stress and plant-pathogen interaction. Currently, next generation sequencing platforms are used to obtain a high amount of raw data to build the transcriptome of any plant. Here, we compare Illumina and Ion Torrent sequencing platforms for the construction and analysis of the holm oak (Quercus ilex) transcriptome. Genomic analysis of this forest tree species is a major challenge considering its recalcitrant character and the absence of previous molecular studies. In this study, Quercus ilex raw sequencing reads were obtained from Illumina and Ion Torrent and assembled by three different algorithms, MIRA, RAY and TRINITY. A hybrid transcriptome combining both sequencing technologies was also obtained in this study. The RAY-hybrid assembly generated the most complete transcriptome (1,116 complete sequences of which 1,085 were single copy) with a E90N50 of 1,122 bp. The MIRAIllumina and TRINITY-Ion Torrent assemblies annotated the highest number of total transcripts (62,628 and 74,058 respectively). MIRA-Ion Torrent showed the highest number of shared sequences (84.8%) with the oak transcriptome. All the assembled transcripts from the hybrid transcriptome were annotated with gene ontology grouping them in terms of biological processes, molecular functions and cellular components. In addition, an in silico proteomic analysis was carried out using the translated assemblies as databases. Those from Ion Torrent showed more proteins compared to the Illumina and hybrid assemblies. This new generated transcriptome represents a valuable tool to conduct differential gene expression studies in response to biotic and abiotic stresses and to assist and validate the ongoing Q. ilex whole genome sequencing

Identification of Proteases and Protease Inhibitors in Seeds of the Recalcitrant Forest Tree Species Quercus ilex.

Proteases and protease inhibitors have been identified in the recalcitrant species Quercus ilex using in silico and wet methods, with focus on those present in seeds during germination. In silico analyses showed that the Q. ilex transcriptome database contained 2,240 and 97 transcripts annotated as proteases and protease inhibitors, respectively. They belonged to the different families according to MEROPS, being the serine and metallo ones the most represented. The data were compared with those previously reported for other Quercus species, including Q. suber, Q. lobata, and Q. robur. Changes in proteases and protease inhibitors alongside seed germination in cotyledon and embryo axis tissues were assessed using proteomics and in vitro and in gel activity assays. Shotgun (LC-MSMS) analysis of embryo axes and cotyledons in nonviable (NV), mature (T1) and germinated (T3) seeds allowed the identification of 177 proteases and 12 protease inhibitors, mostly represented by serine and metallo types. Total protease activity, as determined by in vitro assays using azocasein as substrate, was higher in cotyledons than in embryo axes. There were not differences in activity among cotyledon samples, while embryo axis peaked at germinated T4 stage. Gel assays revealed the presence of protease activities in at least 10 resolved bands, in the Mr range of 60-260 kDa, being some of them common to cotyledons and embryo axes in either nonviable, mature, and germinated seeds. Bands showing quantitative or qualitative changes upon germination were observed in embryo axes but not in cotyledons at Mr values of 60-140 kDa. Proteomics shotgun analysis of the 10 bands with protease activity supported the results obtained in the overall proteome analysis, with 227 proteases and 3 protease inhibitors identified mostly represented by the serine, cysteine, and metallo families. The combined use of shotgun proteomics and protease activity measurements allowed the identification of tissue-specific (e.g., cysteine protease inhibitors in embryo axes of mature acorns) and stage-specific proteins (e.g., those associated with mobilization of storage proteins accumulated in T3 stage). Those proteins showing differences between nonviable and viable seeds could be related to viability, and those variables between mature and germinated could be associated with the germination process. These differences are observed mostly in embryo axes but not in cotyledons. Among them, those implicated in mobilization of reserve proteins, such as the cathepsin H cysteine protease and Clp proteases, and also the large number of subunits of the CNS and 26S proteasome complex differentially identified in embryos of the several stages suggests that protein degradation via CNS/26S plays a major role early in germination. Conversely, aspartic proteases such as nepenthesins were exclusively identified in NV seeds, so their presence could be used as indicator of nonviability.This research was funded by the Spanish Ministry of Economy and Competitiveness in the framework of Projects BIO2015- 64737-R and PID2019-109038RB-I00.S

DISTRIBUCIÓN ESPACIAL Y FLUCTUACIÓN POBLACIONAL DE PHYLLOCOPTRUTA OLEIVORA (ASHMEAD) (ACARI: ERIOPHYIDAE) EN CÍTRICOS DE GÜEMEZ, TAMAULIPAS

The present investigation was accomplished in the county of Güemez, Tamaulipas, Mexico during the period june of 1998 to October of 1999. The objectives were to evaluate the spatial distribution and the population fluctuation of the citrus rust mite Phyllocoptruta oleivora (Ashmead). This investigation was conducted on 10 orange trees of the variety Valencia selected at random in an area of a hectarea. Each tree was divided into 7 sampling areas. Samples were taken every 14 days, using the leaf as the sample unit and counting the number of mites present on both sides of the leaves. A total of 10 leaves were observed in each of 7 sections, making a total of 70 leaves for each tree and 700 for each sampling date. Using the mean densities and the variance obtained in each sampling, a statistical analysis was conducted to determine the spatial distribution of the mite in the area study. Eight indexes were used to determine the spatial distribution. The index values of Lexis , Charlier, David & Moore, Green and the dispersion parameter (K) of negative binomial indicated a clumped distribution for this mite over all 16 sampling dates. However the values of Morisita, Iwao, and Taylor´s power law showed random distribution in two, two, and three sampling dates, respectively. In all samples, the highest mite densities were found in the middle tree stratum (with higher aggregation toward last section of tree) followed by bottom and top strata, respectively. Population peaks were found during march 27 th and september 25 th. The dependent variable used to estimate the populate on fluctuation was the mean density of the mites in each sampling date. The independent variables were: temperature, relative humidity and precipitation. A detected positive correlation between the mean density of the mites and temperatures was observed.El presente trabajo de investigación se realizó en el municipio de Güemez, México, en el periodo de Junio de 1998 a Octubre de 1999. Se determinó la distribución espacial y fluctuación poblacional del arador de los cítricos Phyllocoptruta oleivora (Ashmead). Esta investigación se realizó en 10 árboles de naranjo de la variedad Valencia, seleccionados al azar en una superficie de una hectárea. Cada árbol se dividió en 7 áreas de muestreo y se realizaron muestreos cada 14 días, tomando como unidad de muestra las hojas. En total se registró la población en 700 hojas por fecha de muestreo. De los datos obtenidos se realizaron análisis para determinar la distribución espacial que presenta el ácaro en la zona de estudio, utilizando para ello 8 índices de muestro. Se registró la fluctuación poblacional y posibles factores climáticos que pudieran limitar la densidad poblacional. Los índices de Lexis, Charlier, David y Moore, Green y el parámetro K de la binomial negativa indicaron una distribución agregada en todas las fechas de muestreo donde se detectó la presencia de ácaros. Los valores de Morisita, Iwao y la ley de poder de Taylor mostraron disposición aleatoria en dos, dos y tres de las fechas de muestro respectivamente, en las demás se presentó disposición agregada. En todos los muestreos se encontró mayor cantidad de ácaros en el estrato medio seguido del estrato inferior y superior respectivamente. Se detectaron tres picos poblacionales; el 27 de marzo, el 21 de agosto y el 25 de septiembre con promedios de 3.8, 2.9, y 4.5 ácaros por hoja respectivamente. De los factores climáticos evaluados, la temperatura fue el que presentó el coeficiente de correlación mas alto (r=0.69916)