Made available in DSpace on 2015-04-17T14:49:38Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1353340 bytes, checksum: 960259983d017f61365d51ac1741281b (MD5) Previous issue date: 2014-01-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / As an essential element for plant metabolism, potassium has important role as an activator or as cofactor of many enzymes, acting in several metabolic processes. The supply of potassium (K) fertilization can induce several processes, including those related to fruit quality. Thus, K is known as the "quality element". Therefore, it was evaluated the Paluma guava cultivar, subjected to three doses of K in three maturity stages, with the objective of determining its influency on the contents of total and soluble pectins, percentage of pectin s solubilization, the activity of the enzymes of the cell wall and oxidative metabolism. Three doses of K per plants were applied: 50 g de K2O; 100 g de K2O e 150 g de K2O, fixing the doses of N and P of 150 g and 140 g per plant, respectively. The evaluations were performed in the endocarp of the fruits. The classification of the three maturity stages was established according to the skin color. The variables evaluated were: total pectin (TP), soluble pectin (SP), insoluble pectin (IP), and percentage of solubilization of pectic substances (% Sol), activity of the enzymes pectin methylesterase (PME), polygalacturonase (PG), polyphenoloxidase (PPO), peroxidase (POD). The experimental design was the completely randomized in a 3 x 3 factorial scheme (doses of K x maturity stage), with the replication of three plants and 36 fruits from each plant. The dose of 100 g K plant-1 resulted in higher values of TP, IP, lower activities of PME, PG, and lowed activities of oxidative enzymes for both PPO and POD, reflecting on the greater stability of the cell wall and possibly on longer postharvest life of the fruit. / Como um elemento essencial no metabolismo vegetal, o potássio tem importante papel como ativador ou como cofator de muitas enzimas, atuando em vários processos metabólicos. O fornecimento de potássio (K) via adubação pode induzir vários processos, dentre eles os relacionados à qualidade dos frutos. Por isso, o K é conhecido como o ―elemento da qualidade‖. Diante disso, avaliou-se goiabas da cultivar Paluma, submetidas a três doses de K, em três estádios de maturação, com o objetivo de determinar sua influência sobre a porcentagem de solubilização de substâncias pécticas, a atividade de enzimas parede celular e do metabolismo oxidativo. Três doses de K por plantas foram aplicadas: 50 g de K2O; 100 g de K2O e 150 g de K2O, fixando-se as doses de N e P de 150 g e 140 g, respectivamente. As avaliações foram feitas no endocarpo dos frutos. A classificação dos três estádios foi estabelecida de acordo com a coloração da casca. As variáveis analisadas foram: pectina total (PT), pectina solúvel (PS), pectina insolúvel (PI) e percentual de solubilização de substâncias pécticas (%Sol), atividade das enzimas pectinametilesterase (PME), poligalacturonase (PG) e da polifenoloxidase (POP), peroxidase (POD). O delineamento experimental utilizado foi o inteiramente casualizado, em um esquema fatorial 3 x 3 (dose de K x estádio de maturação), sendo as repetições compostas por três plantas e utilizando-se 36 frutos de cada planta. A dose de 100 g de K.planta-1 resultou em maiores valores de PT, PI, menor atividade da PME, PG e menor atividade de enzimas oxidativas, tanto para a PPO como para a POD, refletindo na maior estabilidade da parede celular e possivelmente na maior da vida útil pós-colheita do fruto.

No description available.

Thesis (MSc (Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2002. / Pathogen devastation of food products has been the topic of extensive research efforts worldwide. Fungal infections are foremost amongst these pests, contributing not only to losses in product yield, but also significantly affecting the quality thereof. It is not surprising then that producers of these foodstuffs and their derived products continually strive towards the highest possible product quality. Therefore, it remains imperative that satisfactory methods are implemented to control these fungal pathogens. The current strategies are all hampered by drawbacks, and severe crop losses are still experienced. New technologies are being explored; one such technology is the genetic transformation of plant species. This method has enabled scientists to introduce foreign genes, with known functions and predictable outcomes, into plants. Genes identified to be involved in disease resistance have become the focus of numerous research efforts concerned with the improvement of the plant's innate defence response. This study aimed to enhance disease resistance to fungal pathogens by means of the genetic transformation of two genes previously shown to be involved in disease resistance. These genes encode polygalacturonase-inhibiting proteins (PGIPs) from Phaseolus vulgaris and resveratrol synthase from Vitis vinifera. PGIPs specifically inhibit the action of fungal polygalacturonases (PGs), which are enzymes responsible for the hydrolytic breakdown of plant cell walls. These enzymes were also found to be the first enzymes that are secreted by fungal pathogens during infection of the host plant. Additionally, PGIP-PG interaction results in the existence of molecules involved in the activation of plant defence responses. Resveratrol, the product of resveratrol synthase, exerts its antifungal action by destruction of the microbial cellular membranes. These mentioned genes were transformed alone, and in combination, into Nicotiana tabacum and the resultant transgenic lines were evaluated for enhanced disease resistance and for possible synergistic effects between the transgenes. Several independent transgenic lines were regenerated with genes integrated into the tobacco genome. Almost all the plants harbouring only pgip or vst1 genes also expressed these genes at a high frequency. Some non-expressing lines were identified from the transgenic plants that had integrated both genes, but several lines were obtained expressing both transgenes. Good correlations were observed between transgene product activity and enhanced resistance to the fungus Botrytis cinerea in an antifungal in planta assay. Lines showing the highest PGIP activity and resveratrollevels were more resistant to the pathogen, leading to disease resistance of up to 80% seven days after inoculation in comparison to an untransformed control. These lines maintained their strong inhibition, even three weeks post-inoculation, showing a complete halt in disease development and fungal growth. These results provide good indications of the efficacy of these transgenes in the upregulation of plant defence. However, the study will have to be expanded to include even more transgenic lines to elucidate the possible synergistic effects of these genes. In an additional pilot study, genes encoding for precursors and for the formation of resveratrol were introduced into the yeast Saccharomyces cerevisiae. The resultant recombinant yeast strains were evaluated for their ability to produce the phenolic substance, resveratrol. This compound has been implicated in beneficial aspects relating to human health, including positive effects on atherosclerosis and platelet aggregation as a direct result of its antioxidant and anti-inflammatory activities. Recombinant yeast strains were constructed that expressed genes coding for coenzyme A ligase and resveratrol synthase. These strains were shown to be able to produce the phenolic compound resveratrol from the precursors present in the yeast as well as from the products introduced with the transformation. The resveratrol was complexed with an added glucose moiety. These results are extremely positive, considering the possibility of manipulating wine yeasts to produce resveratrol during the wine fermentation, thereby adding to the health aspects of both red and white wine. This is the first report of the production of this compound by the introduction of genes necessary for its biosynthesis in a foreign host. This study has confirmed the importance of PGIPs and resveratrol in the effort to enhance disease resistance in plants through genetic transformation technology. It has also shown that the health benefits of resveratrol could be exploited more optimally in the wine industry, by producing wine yeasts with the ability to synthesise this important antioxidant.

Thesis (MScAgric (Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Necrotrophic fungi infect many economically important crop plants. This results in great losses in the agricultural sector world-wide. Understanding the nature by which plants respond to pathogens is imperative for genetically enhancing disease resistance in plants. Research tools have significantly contributed to our understanding of how the plant responds to pathogen attack, identifying an array of defence mechanisms used by plants upon attack. Many fungal pathogens secrete endopolygalacturonases (endoPGs) when infecting plants. These hydrolytic enzymes are inhibited by polygalacturonase-inhibiting proteins (PGIPs) associated with plant cell walls. PGIPs are well characterised and their current known functions are all linked to endoPG inhibition and the subsequent upregulation of plant defence pathways. Work on grapevine PGIPs have shown that apart from being efficient antifungal proteins, leading to protection of the plant against Botrytis cinerea when overexpressed, PGIPs might also have additional functions linked to cell wall strengthening. This working hypothesis formed the motivation of this study where a cinnamyl alcohol dehydrogenase (CAD) (1.1.1.195) gene was targeted for functional analysis in tobacco (Nicotiana tabacum). Some previous work and genetic resources obtained is relevant to this study, specifically previously characterized transgenic tobacco lines overexpressing the Vitis vinifera pgip1 (Vvpgip1) gene. These lines have confirmed PGIP-specific resistance phenotypes against B. cinerea, as well as increased levels of CAD transcripts in healthy plants. Moreover, preliminary evaluations indicated increased lignin levels as well as differential expression of several other cell wall genes in these overexpressing lines (in the absence of infections). In this study we generated a transgenic tobacco population, overexpressing the native CAD14 gene, via Agrobacterium transformations. The transgene was overexpressed with the Cauliflower Mosaic Virus promoter (CaMV 35Sp). The CAD transgenic population was analyzed for transgene integration and expression and showed active transcription, even from leaves that normally don’t express CAD to high levels. These lines, together with the untransformed control, and a representative transgenic VvPGIP1 tobacco line previously characterized with elevated expression of CAD were used for all further analyses, specifically CAD activity assays of stems and leaves, as well as whole plant infections with B. cinerea. CAD enzyme activity assays were performed on healthy uninfected plant lines, without inducing native CAD expression or resistance phenotypes (i.e. without Botrytis infection). CAD activity was detected in leaves and stems, but a statistically sound separation between the CAD population and the untransformed control was only observed in the stems. The CAD assays also confirmed previous results that indicated that CAD transcription was upregulated in the PGIP line in the absence of infection. Overall, in all plant lines the stems exhibited 10-fold higher levels of CAD activity than the leaves, but the transgenic VvPGIP1 line showed a further 2-3-fold increase in CAD activity in the stems, when compared to the untransformed control and the majority of the CAD overexpressing lines. Disease assessment by whole plant infections with B. cinerea of the CAD transgenic plants revealed reduced disease susceptibility towards this pathogen. A reduction in disease susceptibility of 20 – 40% (based on lesion sizes) was observed for a homologous group of transgenic lines that was statistically clearly separated from the untransformed control plants following infection with Botrytis over an 11-day-period. The VvPGIP1 transgenic line displayed the strongest resistance phenotype, with reduction in susceptibility of 47%. The reduction in plant tissue maceration and lesion expansion was most pronounced in the VvPGIP1 line compared to the CAD transgenic plants, while the CAD transgenic plants showed more reduction than the untransformed control. In combination, the data confirms that CAD upregulation could lead to resistance phenotypes. Relating this data back to the previously observed upregulation of CAD in the VvPGIP1-overexpressing lines, the findings from this study corroborates that increased CAD activity contributes to the observed resistance phenotypes, possibility by strengthening the cell wall. In conclusion, this study yielded a characterized transgenic population overexpressing the CAD14 gene; this overexpression contributed to increased RNA transcription compared to the untransformed control plant, increased CAD activity (most notably in the stems) and a disease resistance phenotype against Botrytis. These findings corroborates the current working hypothesis in our group that PGIPs might have a role in preparing the plant cell for attack by contributing to specific cell wall changes. The exact mechanisms are still currently unknown and under investigation. The transgenic lines generated in this study will be invaluable in the subsequent analyses where these various phenotypes will be subjected to profiling and accurate cell wall analyses. / AFRIKAANSE OPSOMMING: Nekrotrofiese swamme infekteer en beskadig verskeie ekonomies belangrike gewasse. Dit lei wêreldwyd tot groot verliese vir die landbousektor. Dit is noodsaaklik om te verstaan hoe plante reageer teenoor patogene, sodat die siekteweerstand van plante verbeter kan word. Navorsingshulpbronne het beduidend bygedra tot die kennis van plantreaksies tydens patogeniese aanvalle, en het sodoende ‘n reeks van weerstandmeganismes, wat die plant inspan tydens ‘n aanval, geïdentifiseer. Verskeie patogeniese swamme skei endopoligalakturonases (endoPGs) af tydens plantinfeksie. Hierdie hidrolitiese ensieme word geïnhibeer deur poligalakturonase-inhiberende proteïene (PGIPs) wat met die plantselwand geassosieerd is. PGIPs is goed gekarakteriseerd en al hulle huidiglik bekende funksies is gekoppel aan endoPG inhibisie en die daaropvolgende opregulering van plant weerstandspaaie. Navorsing op wingerd PGIPs het gewys dat, afgesien van die feit dat PGIPs goeie antifungiese proteïene is wat lei tot beskerming van die plant teen Botrytis cinerea wanneer dit ooruitgedruk word, PGIPs ook moontlik addisionele funksies verrig wat verwant is aan selwandversterking. Hierdie werkshipotese vorm die motivering vir hierdie studie waarin ‘n sinnamiel alkohol dehidrogenase (SAD) (1.1.1.195) geen geteiken is vir funksionele analise in tabak (Nicotiana tabacum). Vorige navorsing en genetiese hulpbronne daardeur verkry is belangrik vir hierdie studie, spesifiek die gekarakteriseerde transgeniese tabaklyne wat die Vitis vinifera pgip1 (Vvpgip1) geen ooruitdruk. Hierdie lyne besit bevestigde PGIP-spesifieke weerstandsfenotipes teen B. cinerea, sowel as hoër vlakke van SAD transkripte in gesonde plante. Voorlopige analises het ook aangedui dat hierdie ooruitdrukkende lyne hoër lignien vlakke het, asook differensiële uitdrukking van verskeie ander selwandgene (in die afwesigheid van infeksie). In hierdie studie is ‘n transgeniese tabakpopulasie gegenereer wat die natuurlike tabak SAD14 geen ooruitdruk, deur middel van Agrobacterium transformasie. Die transgeen is ooruitgedruk deur die Blomkool Mosaïek Virus promoter (CaMV 35Sp). Die SAD transgeniese populasie is geanaliseer vir transgeen integrasie en uitdrukking en het aktiewe transkriptering getoon, selfs in blare waar daar normaalweg nie hoë vlakke van SAD uitgedruk word nie. Hierdie lyne, die ongetransformeerde wilde-tipe kontrole sowel as ’n verteenwoordigende transgeniese VvPGIP1 tabaklyn wat vooraf gekarakteriseerd was met hoë SAD uitdrukking, is gebruik vir alle verdere analises, spesifiek SAD aktiwiteitstoetse in stingels en blare, asook heelplantinfeksies met B. cinerea. Aktiwiteitsanalises van die SAD ensiem is gedoen op gesonde ongeinfekteerde plantlyne, sonder om natuurlike tabak SAD uitdrukking of weerstandsfenotipes te induseer (dus sonder Botrytis infeksie). SAD aktiwiteit is waargeneem in beide die blare en stingels, maar ‘n statisties betekenisvolle skeiding is slegs gevind tussen die SAD populasie en die ongetransformeerde kontrole in die stingels. Die SAD toetse het ook vorige resultate bevestig wat aangedui het dat SAD transkripsie opgereguleer word in die PGIP lyn in die afwesigheid van infeksie. Die stingels het oor die algemeen ‘n 10-voudige vermeerdering in SAD aktiwiteitsvlakke getoon in vergelyking met die blare, maar die transgeniese VvPGIP1 lyn het ‘n verdere 2-3-voudige verhoging in SAD aktiwiteit gehad in die stingels ,in vergelyking met die ongetransformeerde kontrole en die meerderheid van die SADooruitdrukkende lyne. Siekteweerstand ondersoeke deur middel van heelplantinfeksies met B. cinerea van die SAD transgeniese plante, het verminderde vatbaarheid aangedui ten opsigte van hierdie patogeen. ‘n Afname in siekte-vatbaarheid van 20 – 40% (gebaseer op wondgroottes) is waargeneem vir ‘n homoloë groep transgeniese lyne wat statisties betekenisvol geskei kon word van die ongetransformeerde kontrole plante na infeksie met Botrytis in ‘n infeksietoets wat 11 dae geduur het. Die VvPGIP1 transgeniese lyn het die mees weerstandbiedende fenotipe gehad, met ‘n afname in siekte-vatbaarheid van 47%. Die afname in plantweefselafbreking en wondgrootte was die duidelikste in die VvPGIP1 lyn in vergelyking met die SAD transgeniese plante, terwyl die SAD transgeniese plante ‘n groter afname aangedui het as die ongetransformeerde kontrole. In kombinasie het die data bevestig dat SAD opregulasie kan lei tot weerstandbiedende fenotipes. Hierdie data, in vergelyking met die vorige bevinding van opregulasie van SAD in die VvPGIP1-ooruitdrukkende lyne, bevestig dat hoër SAD aktiwiteit bydra tot die waargenome weerstandbiedende fenotipes, moontlik deur versterking van die plantselwand. Ter afsluiting, hierdie studie het ‘n gekarakteriseerde transgeniese populasie wat die SAD14 geen ooruitdruk gelewer; hierdie ooruitdrukking het bygedra tot hoër RNA transkripsie in vergelyking met die kontrole, verhoogde SAD aktiwiteit (veral in die stingels) en siekteweerstandbiedende fenotipes teenoor Botrytis. Hierdie bevindinge ondersteun die huidige werkshipotese in ons groep dat PGIPs moontlik ‘n rol speel in die voorbereiding van die plantsel teen infeksie deur spesifieke selwandveranderinge te veroorsaak. Die spesifieke meganismes is steeds onbekend en word verder ondersoek. Die transgeniese lyne wat tydens hierdie studie gegenereer is, sal baie belangrik wees in opvolgende analises waar hierdie verskillende fenotipes gebruik kan word om die profiel van selwandkomponente, maar ook die akkurate selwandsamestelling te bestudeer.

Made available in DSpace on 2014-12-17T15:01:45Z (GMT). No. of bitstreams: 1 SHARLINEFMS.pdf: 1463401 bytes, checksum: ffe101fa6bbf11d2b6fe49f4d837a15c (MD5) Previous issue date: 2007-12-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Pectinolytic enzymes, or simply pectinases, are complex enzymes that degrade pectic polymers. They have many uses, such as fruit juice extraction and purification, textile fiber treatment and vegetal oil extraction. The aim of this work was to study the kinetics of pectinases production by solid-state fermentation, using dry cashew apple residue as substrate and the microorganism Aspergillus niger CCT 0916. The influence of the initial medium moisture and medium supplementation with a source of nitrogen and phosphorus was evaluated using the factorial experimental planning and response surface methodology. Ammonia sulphate and potassium phosphate were used as nitrogen and phosphorus source, respectively. The variables time of contact (T) and ratio volume solvent/fermented medium (RZ), in systems with and without agitation, were evaluated in order to study the best extraction condition of the produced enzyme. Washed and unwashed cashew apple residues were tested as the growth medium. The unwashed residue was obtained by drying the residue after the extraction of the juice, while the washed residue was obtained by water washing 5 times using the proportion of 1 kg pulp/2 liters of water. Samples were taken every 12 hours for moisture content, pH, protein, reducing sugars, polygalacturonase activity (PG) and viscosity reduction. The physical-chemical composition of the residues had different sugar and pectin levels. For the unwashed residue, the peak activity was reached with 40% of initial moisture content, 1% of nitrogen supplementation without phosphorus addition after 30 hours of process. These conditions led to 16 U/g of PG activity and 82% of viscosity reduction. The calculated models reached similar values to the experimental ones in the same process conditions: 15.55 U/g of PG and 79.57% of viscosity eduction. Similarly, the greatest enzyme production for washed residue was reached with 40% initial moisture content, 1% nitrogen supplementation without phosphorus addition after 22 hours of cultivation. In this condition it was obtained polygalacturonase activity of 9.84 U/g and viscosity reduction of 81.36%. These values are close to experimental values that were of 10.1 U/g and 81%, respectively. The conditions that led to the best PG activity results was the agitated one and the best extraction condition was obtained with 100 minutes of solvent/medium contact and RZ of 5 (mL/g) / As enzimas pectinol?ticas ou pectinases formam um grupo heterog?neo de enzimas que hidrolisam as subst?ncias p?cticas, s?o usadas na extra??o de suco de fruta e sua clarifica??o, tratamento de fibra t?xtil e extra??o de ?leo vegetal. O objetivo deste trabalho foi o estudo da produ??o de pectinases (cin?tica fermentativa) atrav?s da fermenta??o em estado s?lido, usando como substrato o ped?nculo de caju seco e como agente da fermenta??o o microrganismo Aspergillus niger CCT 0916. Utilizando a metodologia do planejamento experimental fatorial e an?lise de superf?cie de resposta estudou-se a influ?ncia da umidade inicial do meio, suplementa??o do meio com fonte de nitrog?nio e fonte de f?sforo. Como fonte de nitrog?nio foi utilizado o sulfato de am?nia e como fonte de f?sforo o fosfato de pot?ssio monob?sico. Estudou-se, tamb?m, a melhor condi??o de extra??o da enzima produzida do meio de fermenta??o. Neste caso, foram estudadas as vari?veis: raz?o volume de solvente/gramas de meio fermentado e tempo de contato entre as fases, utilizando-se dois sistemas de extra??o com e sem agita??o. Como meio de cultivo foram utilizados dois res?duos do ped?nculo de caju: res?duo sem lavar e res?duo lavado. Estes res?duos diferem devido ao tratamento dado antes da secagem. O sem lavar foi obtido secando o res?duo ap?s a extra??o do suco, enquanto que o lavado, foi obtido lavando-se com ?gua, cinco vezes, ap?s a extra??o do suco, na propor??o 1 kg de baga?o para 2 litros de ?gua. A caracteriza??o f?sico-qu?mica dos res?duos mostrou composi??es diferentes, principalmente em rela??o aos teores de a??cares redutores e pectina. Durante o cultivo foram analisados, em intervalos de aproximadamente 12 horas, umidade do meio, pH, teor de prote?na, a??cares redutores, atividade da poligalacturonase (PG) e o percentual de redu??o de viscosidade. Para o res?duo sem lavar o pico de atividade foi com 40% de umidade e 1% de nitrog?nio, sem adi??o de f?sforo, com 30 horas de cultivo sendo 16 U/g de atividade de PG e 82% de redu??o de viscosidade. As equa??es emp?ricas obtidas fornecem valores bem pr?ximos aos experimentais nas mesmas condi??es de processo, 15,55 U/g de PG e 79,57% de redu??o de viscosidade para o res?duo sem lavar. Assim como para o res?duo sem lavar, para o res?duo lavado os picos de produ??o da enzima ocorreram para as mesmas condi??es de processo: umidade de 40%, nitrog?nio de 1%, sem adi??o de f?sforo, com 22 horas de cultivo. Nesta condi??o, obteve-se atividade da poligalacturonase de 9,84 U/g e percentual de redu??o de viscosidade de 81,36%. Estes valores est?o bem pr?ximos aos valores experimentais que foram de 10,1 U/g de PG e 81%, respectivamente. Na extra??o da PG o sistema que apresentou os melhores resultados de atividade foi o operado com agita??o e a melhor condi??o de extra??o foi com o tempo de contato solvente com o meio de fermenta??o de 100 minutos e a raz?o volume de solvente com o meio fermentado 5 (mL/g)

No description available.

Ophiostoma novo-ulmi is the causal agent of Dutch elm disease (DED) which has had a severe impact on the urban landscape in Canada. This research program focused on developing molecular genetic strategies to control this pathogenic fungus. The first strategy involved the development of RNA interference (RNAi) for the down-regulation of genes involved in pathogenicity. An efficient RNAi cassette was developed to suppress the expression of the endopolygalacturonase (epg1) locus which encodes a cell-wall degrading enzyme. This epg1-RNAi cassette significantly reduced the amount of polygalacturonase activity in the fungus and resulted in almost complete degradation of epg1 mRNA. The need for a native promoter to selectively down-regulate specific gene loci was addressed by developing a carbon-catabolite regulated promoter (alcA) to drive the expression of the epg1-RNAi cassette. The expression of an alcA-driven epg1-RNAi cassette resulted in the down-regulation of epg expression under glucose starvation but normal levels of expression in high glucose. The expression could therefore be controlled by culture conditions. The second strategy explored the potential of using dsRNA viruses to vector disruptive RNAi cassettes. An isolate of O. novo-ulmi strain 93-1224 collected in the city of Winnipeg, was infected by two dsRNA mitoviruses which upon sequence characterization were named OnuMV1c and OnuMV7. To assess the transmissibility of this dsRNA virus the infected isolate 93-1224 was paired with three naive isolates of the related fungi O. ulmi and O. himal-ulmi. Through the use of nuclear and mitochondrial markers it was determined that the virus OnuMV1c may not rely on mitochondrial fusion for transmission but may have a cytoplasmic transmission route. This investigation of gene expression and manipulation has provided tools to help understand gene regulation in O. novo-ulmi. It has also added to our knowledge of mitoviruses, their transmission and potential use as a biological control. By enhancing our understanding of transmissible hypovirulence this work contributes to efforts to develop a new approach to target DED as well as a potential model for the control of other fungal diseases. / Graduate / 0307 / 0306 / 0369 / jscarneiro@hotmail.com