Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O feijão-caupi constitui-se uma das leguminosas de grande importância para o Estado de Roraima e seu cultivo pode ser encontrado em diversas áreas da região. É uma leguminosa que pode beneficiar da fixação biológica de nitrogênio, através da simbiose com bactérias do gênero Bradyrhizobium. Desta forma, objetivou-se neste trabalho caracterizar e avaliar a eficiência simbiótica de 41 estirpes de rizóbios isoladas de ambientes de mata e cerrado em Roraima. As estirpes foram caracterizadas morfologicamente e agrupadas de acordo com os perfis gerados, em seguida foram caracterizadas geneticamente através da amplificação e sequênciamento parcial do gene 16S rRNA. Utilizando o feijão-caupi como planta isca, foi conduzido um experimento em casa de vegetação para avaliação da eficiência simbiótica, do qual determinou-se a matéria seca da parte aérea, número e massa seca de nódulos. Deste experimento, oito estirpes que se mostraram mais eficientes foram testadas em campo. No campo dois experimentos foram conduzidos, um em área sem cultivo anterior com feijão-caupi e outro em área cultivada por dois anos. Dos experimentos de campo, aos 30 dias foram avaliados, massa seca e N-total da parte aérea, número e massa seca de nódulos e no final do ciclo determinou-se a produtividade de grãos. Do total de estirpes caracterizadas, a maioria apresentou crescimento lento (58%) e reação neutra (51 %) do meio de cultura, características que foram compatíveis com as do gênero Bradyrhizobium. A análise do sequênciamento parcial do gene 16S rRNA revelou que as estirpes obtidas de feijão-caupi apresentam elevada diversidade fenotípica e genotípica, com predominância de estirpes do gênero Bradyrhizobium e em menor proporção estirpes com características semelhantes ao gênero Rhizobium. Os resultados obtidos no ensaio de eficiência simbiótica mostrou que 20 estirpes foram eficientes, sendo todas pertencentes ao gênero Bradyrhizobium. Três estirpes (ERR 24, ERR40 e ERR 510) apresentam bons resultados para os atributos avaliados em condições de campo, apresentado valores satisfatórios quanto à eficiência simbiótica igual ou superior as estirpes atualmente recomendadas e ao controle nitrogenado, sendo indicadas como novos inoculantes. / The cowpea constitutes one of the legume plants of great importance to the State of Roraima and its cropping can be found in several areas of the region. It is a legume plant which can benefit from the biological fixation through symbiosis with bacteria of the genus Bradyrhizobium. In this way, it was aimed in this work to characterize and evaluate the symbiotic efficiency of strains of rhizobia isolated from Forest and cerrado (savannah-like vegetation) environment in Roraima. The strains were characterized morphologically and grouped together according to the profiles generated; next, they were characterized genetically through the amplification and partial sequencing of gene 16S rRNA. Utilizing the cowpea as a bait plant, an experiment was conducted in a greenhouse for evaluating of the symbiotic efficiency, from which the dry matter of the shoot, number and dry matter of nodules were determined. Of this experiment, eight strains which proved more efficient were tested in field. In the field, two experiments were conducted, one in an area with no previous cropping with cowpea and the other in an area cultivated for two years. Of the Field experiments, at 30 days, dry matter and total-N of the shoot, number and dry mass of nodules were evaluated and at the end of the cycle, grain yield was determined. Of the total of strains characterized, most of them presented slow growth (58%) and neutral reaction (51 %) of the culture medium, characteristics which were consistent with those of the genus Bradyrhizobium. The analysis of the partial sequencing of gene 16SrRNA revealed that the strains obtained of cowpea present a high phenotypic and genotypic diversity, with predominance of strains of the genus Bradyrhizobium ADN to a smaller extent strains with characteristics similar to the genus Rhizobium. The results obtained in the symbiotic efficiency assay showed that 20 strains were efficient, all of them belonging to the genus Bradyrhizobium. Three strains (ERR 24, ERR40 and ERR 510) present good results as regards the symbiotic efficiency for the attributes evaluated under field conditions, presenting satisfactory values concerning the symbiotic efficiency equal or superior to the strains currently recommended and to the nitrogen-containing control, they being recommend as new inoculants.

MSCAGR (Animal Science) / Department of Animal Science / The Nguni is a transboundary indigenous Southern African cattle breed. The breed has distinct populations that are adapted to the different ecological zones of Southern Africa. Previous work on characterising the Nguni has been limited to within-country studies. Thus, the aim of the current study was to genetically characterise South African (SA) Nguni, Mozambican Nguni (Landim) and Swazi Nguni populations across Southern African region using a panel of 25 microsatellite markers, recommended by FAO and ISAG for genetic diversity studies. Genotypic data were generated from 90 unrelated autosomal DNA samples of the three cattle populations (SA Nguni n=30, Mozambican Nguni (Landim) n=30 and Swazi Nguni n=30) collected from government research stations and stud herds. Five South African beef cattle breeds’ DNA profiles were obtained from the ARC-DNA database and used as reference populations. A majority of the microsatellite markers were highly polymorphic across the studied populations. High genetic diversity was detected and expected heterozygosity varied from 71% (Landim) to 75% (SA Nguni) with a higher mean number of alleles (MNA) in the SA Nguni (7.52±0.42) compared to the Swazi Nguni (6.92±0.40) and Landim (7.16±0.43) populations. Observed heterozygosity (Ho) (0.597±0.046) compared to expected heterozygosity (He) (0.719±0.022) was lowest for the Swazi Nguni, confirming a relatively high level of inbreeding (FIS=0.158) in that population. An analysis of molecular variance (AMOVA) revealed that 9.61% of the total variation occurred among populations, while 90.39% occurred within populations. Short genetic distance (29.9%) was observed between Landim and Swazi Nguni, with the SA Nguni (>50%) being the most genetically distant population. The distant relationship between SA Nguni and the other two Nguni cattle populations was further confirmed by neighbor-joining (NJ) tree, Principal Coordinates Analyses (PCoA) and Factorial Corresponding Analysis (FCA). The structure of the three Nguni cattle populations clustered independently, despite some evidence of admixture. Additionally, genetic differentiation and population structure within four Mozambican indigenous cattle populations were investigated using the same panel of microsatellite markers. The analysis of unrelated autosomal DNA was performed on 120 animals (Angone n=30, Bovine de Tete n=30, Landim n=30 and Namaacha Nguni n=30), which presented sufficient genetic diversity across all populations. Estimates of mean number of alleles, observed and expected heterozygosities were 6.920±0.20, 0.68±0.02 and 0.71±0.01, respectively. Genetic differentiation among the populations accounted for 8.02% of total genetic variability. Negative (-0.025±0.029) to low positive (0.073±0.050) levels of inbreeding were observed within the four populations. The genetic distance, NJ tree, PCoA and FCA revealed a close relationship between Bovine de Tete and Landim as opposed to Angone and Namaacha Nguni. STRUCTURE analysis assigned the four Mozambican populations independently; however Bovine de Tete and Landim showed relatively higher levels of admixture with each other than Angone and Namaacha Nguni. It can be concluded that SA Nguni, Landim and Swazi Nguni populations accomplish high genetic diversity and they are genetically distant; however, the two latter populations are closely related. These results present useful information / NRF

Made available in DSpace on 2015-04-20T12:31:32Z (GMT). No. of bitstreams: 1 Aloisio Freitas Chagas Junior.pdf: 1425510 bytes, checksum: 861fcee7c2ea43864c650307852db610 (MD5) Previous issue date: 2007-04-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / To increase the rhizobia contribution to plants nutrition and development is necessary to develop researches for selecting more efficient nitrogen fixation strains. This research work had as objectives, to accomplish morphologic characterization of rhizobia isolated from Amazonian soils; laboratory evaluations about the tolerance to acidity and toxic Al, the capacity to solubilize calcium (P-Ca) and aluminum (P-Al) phosphates, the indole-acetic acid production (AIA); the ability of the isolates to induce nodulation and to fix nitrogen under the acidity and low fertility conditions of the regional soils in greenhouse experiment; to genetically characterize the isolated ones selected using the PCR-RFLP technique. The infectivity test showed that there was significant increase in the cowpea biomass. With relationship to the phenotypic characterization, the 200 isolates showed a great diversity. Among these, 165 and 127 presented high tolerance within the media with pH 4,5 and pH 4,5 + Al, respectively. From the 200 isolates, 68 solubilized P-Ca and 47 P-Al, and 32 isolates solubilized both P-Ca and P-Al. The AIA production significantly increased (p <0,01) with tryptophan quantities added in the medium for 19 of the 92 isolates tested in the experiment. It was observed production of dry matter and nodule number and mass superior simbiotic to the control treatment and similar to the fertilized treatment for various rhizobia isolates. The 20 selected isolates evaluated presented high genotypic diversity, with the derived dendrogram PCR-RFLP profiles showing that they can be divided inside two main genders, Rhizobium and Bradyrhizobium. Associating the results of simbiotic efficiency and nodulation, it was observed that the isolates of rhizobia from Amazonian soils presented good results, and they can be recommended for tests of agronomic efficiency for cowpea bean. / Para aumentar a contribuição de rizóbia na nutrição e desenvolvimento de plantas é necessário desenvolver pesquisas de seleção de estirpes mais eficientes quanto à fixação do N2. Este trabalho teve como objetivos, realizar a caracterização morfológica de isolados de rizóbio oriundos de solos amazônicos; avaliar em laboratório, a tolerância à acidez e Al tóxico, a capacidade de solubilização de fosfato de cálcio (P-Ca) e alumínio (P-Al), a produção de acido indol-acético (AIA); a capacidade de isolados em induzirem nodulação e fixarem nitrogênio sob as condições de acidez e baixa fertilidade dos solos regionais em casa-de-vegetação; caracterizar geneticamente os isolados selecionados usando a técnica de PCR-RFLP. Os testes de infectividade mostraram que houve aumento significativo na biomassa de caupi. Quanto à caracterização fenotípica, os 200 isolados mostraram uma grande diversidade. Dentre estes, 165 e 127 isolados apresentaram elevada tolerância nos meios de cultura com pH 4,5 e pH 4,5 + Al, respectivamente. Dos 200 isolados testados, 68 solubilizaram P-Ca e 47 P-Al, sendo que 32 solubilizaram tanto o P Ca quanto o P Al. A produção de AIA aumentou significativamente com as doses de triptofano adicionadas ao meio (p<0,01) para 19 dos 92 isolados testados no experimento. Observou-se produção de matéria seca, número e massa seca dos nódulos e acúmulo de nitrogênio superiores ao tratamento testemunha e similares ao tratamento adubado para vários isolados de rizóbia. Os 20 isolados selecionados e avaliados apresentaram alta diversidade genotípica, onde o dendrograma derivado de perfis de PCR-RFLP mostrou que podem ser divididos dentro de dois gêneros principais, Rhizobium e Bradyrhizobium. Associando-se os resultados de eficiência simbiótica e nodulação, observou-se que os isolados de rizóbio de solos da Amazônia apresentaram bom desempenho e podem ser recomendados para testes de eficiência agronômica em feijão caupi.

Aspergillus westerdijkiaem qui est récemment démembré d'A. ochraceus est un producteur principal de plusieurs composés de type polycétone d'importance économique. Ces composés incluent l’ochratoxin A, mellein, l'acide penicillique, asperlactone et l’isoasperlactone et quelques intermédiaires comme l'acide 6- methylsalicylique et l’acide orsellinique. La biosynthèse de ces métabolites est catalysée par un groupe d'enzymes connues comme la polycétone synthases (PKSs). Ce travail a été visé pour cloner et a caractérisé fonctionnellement les différentes genes des PKS i.e. aoks1, aolc35-12 et aomsas, et de genes de polyketide synthases-non ribosomal peptide synthase (PKS-NRPS) i.e. aolc35-6, chez A. westerdijkiae. Ces gènes ont été inactivés par l'insertion du gène d’hygromycine B phosphotransferase d’Escherichia coli dans le génome d'A. westerdijkiae, pour obtenir les mutantes ao?ks1, ao?lc35-12, ao?msas et ao?lc35-6. Les mutants ao?ks1 et ao?lc35-12 ont été trouvés déficients dans la biosynthèse d’ochratoxin A, mais produisaient encore mellein. À notre connaissance, c’est la première fois que nous avons caractérisé les gènes impliquées dans la biosynthèse d’OTA, sachant que mellein, qui était proposé dans la littérature comme un intermédiaire, joue a cune role dans la biosynthesis de l'OTA. Ensuite le mutant ao?msas n'a pas seulement perdu la capacité de produire isoasperlactone et asperlactone, mais aussi il ne produit pas l’intermédiaire acide 6-methylsalicylique. Basé sur les expériences de la caractérisation génétique et de complémentation chimiques, nous avons proposé un shéma hypothétique de la biosynthèse d’asperlactone et isoasperlactone dans lequel l'acide 6-methylsalicylique, diepoxide et aspyrone jouent le rôle d’intermédiaires. La techniques de gène knock-out et de la reverse transcription PCR (RT-PCR) ont montré que seulle gène de type PKS-NRPS « aolc35-6 » identifié chez A. westerdijkiae codant pour un intermédiaire inconnu(s) qui pourrait inciter l'expression de gène aomsas et un gène impliqué dans la biosynthèse d'acide orsellinique et d'acide penicillique. / Aspergillus westerdijkiaem which is recently dismembered from A. ochraceusm is the principal producer of several economically important polyketide metabolites. These metabolites include ochratoxin A, mellein, penicillic acid, asperlactone and isoasperlactone and some intermediates like orsellinic acid and 6-methylsalicylic acid. The biosynthesis of these metabolites is catalyzed by a group of enzymes known as polyketide synthases (PKSs). This work was aimed to clone and functionally characterized various PKS i.e. aoks1, aolc35-12 and aomsas, and polyketide synthasesnon ribosomal peptide synthase (PKS-NRPS) genes i.e. aolc35-6, in A. westerdijkiae. These genes were inactivated by the insertion of Escherichia coli hygromycin B phosphotransferase gene in the genome of A. westerdijkiae to obtain ao?ks1, ao?lc35-12, ao?msas and ao?lc35-6 mutants. ao?ks1, ao?lc35-12 mutants were found deficient in ochratoxin A biosynthesis but are still producing mellein. To our knowledge, we for the first time characterized a gene involved in OTA biosynthesis, with the information about mellein which was proposed in the literature to be an intermediate OTA. Further ao?msas mutant not only lost the capacity to produce isoasperlactone and asperlactone but also the intermediate nature product 6-methylsalicylic acid. Based on the genetic characterization and chemical complementation experiments, we have proposed a hypothetical pathway mentioning that 6-methylsalicylic acid, diepoxid and aspyrone are intermediates of isoasperlactone and asperlactone. Gene knockout technique and reverse transcription PCR (RT-PCR) shown that the only PKS-NRPS gene aolc35-6 so far identified in A. westerdijkiae encoding certain unknown intermediate(s) which induces the expression of aomsas gene and a gene involved in the biosynthesis of orsellinic acid and penicillic acid.