Over the past decade, the Eastern Shore of Virginia (ESV) has been implicated in at least four outbreaks of Salmonellosis associated with tomato all originating from the same strain, Salmonella enterica serovar Newport.  In addition to S. Newport contamination, the devastating plant disease, bacterial wilt, caused by the phytopathogen Ralstonia solanacearum threatens the sustainability of ESV tomato production.  Bacterial wilt is present in most ESV tomato fields and causes devastating yield losses each year.  Due to the ESV\'s endemic population of R. solanacearum and S. Newport, the relationship between the two pathogens is of interest and has never been investigated.  Two separate studies were conducted to assess the relationship between these two bacteria.  One study consisted of a series of greenhouse trials that involved root-dip inoculations of tomato plants with one of four treatments: 1) S. Newport, 2) R. solanacearum, 3) a co-inoculation of S. Newport + R. solanacearum, and 4) a control group with no inoculation. Leaf, stem, and fruit samples were collected from the plants and S. enterica presence from the internal tissues was observed.  S. enterica was recovered from a low percentage of fruit and leaf samples.  There were significantly more stem samples from plants co-inoculated with S. Newport + R. solanacearum positive for S. enterica (17.46%) than from other treatments.  Another study examined the relationship between the two bacteria via vacuum infiltration inoculations of tomato fruit collected from commercial production fields on the ESV with S. Newport.  Tomato fruit were collected from plants expressing symptoms of bacterial wilt (symptomatic) and plants not expressing bacterial wilt symptoms (asymptomatic).  After fruit infiltration with S. Newport, recovery concentration of S. enterica from internal tissues was measured.  S. enterica populations were greater in fruit originating from asymptomatic (5.15 log CFU/g) versus symptomatic (4.91 log CFU/g) plants across five studies.  Fruit collected from asymptomatic plants had a significantly higher internal pH (4.60) than fruit collected from symptomatic plants (4.37).  These results suggest that R. solanacearum can influence S. enterica survival and transportation throughout the internal tissues of tomato plants as well as the influence internal tomato fruit pH, which could potentially impact S. Newport survival in the fruit. / Master of Science in Life Sciences

No description available.

In 2007 and 2008 more than 100 million dollars of fresh market tomatoes were grown in Virginia, with the majority of production occurring on the Eastern Shore of Virginia (ESV), according to the National Agricultural Statistics Service. Bacterial wilt of tomato, caused by Ralstonia solanacearum (Smith) and Yabucchi et al., is the most devastating disease of tomato on the ESV. Four 'observational trials' were conducted on the ESV over three growing seasons to determine the temporal and spatial distribution of this disease in commercial tomato fields. Plants were assessed at approximately one-week intervals throughout the growing seasons and the incidence of bacterial wilt for each individual plant was recorded. A steady increase in both disease incidence and clustered distribution of the disease within rows was observed as the growing season progressed. Positive correlations between disease incidence and percentage of rows exhibiting a significant clustered distribution occurred in all trials, which indicated an increase in clustered distribution as disease incidence increased. Research trials were conducted over three years, beginning in the summer of 2007, to investigate the effects of tomato bacterial wilt resistant cultivars on the ESV. In 2008 and 2009, the selective, systemic compound which induces host plant resistance, acibenzolar-S-methyl (ASM) was incorporated into resistant cultivar trials. Results from the 2007 trial revealed significant resistance in some of the breeding lines, CRA 66 and PI 126408. The 2008 and 2009 trials revealed that ASM was not effective at reducing levels of bacterial wilt. Grafted transplants in the spring trials of 2008 and 2009 had varied results in resistance and yield. Results revealed the tomato cultivar BHN 669 was an excellent resistant cultivar with promising yield potential and fruit quality. / Master of Science

The genus Gluconobacter is industrially important due to the ability to accomplish unusual and almost complete oxidation reactions (bioconversions) and to contaminate high sugar content products. Following preliminary evidence that some strains of Gluconobacter were resistant to cadmium, and realizing that cadmium resistance among gram-negative organisms is often encoded by an operon which also encodes cobalt and zinc resistance via an efflux mechanism, 10 strains of Gluconobacter were tested for heavy-metal resistance. Three of the 10 representative strains appeared to be resistant to cadmium chloride, and two were also resistant to cobalt- and zinc chloride. These strains, as well as two cadmium-sensitive strains were analyzed using PCR and sequencing to establish gene homology with Ralstonia eutropha, the most frequently studied Gram-negative bacterium exhibiting cadmium resistance. Amplification of two genes from the czc operon, known to encode cadmium, cobalt and zinc resistance in Ralstonia, was attempted in the three resistant and two sensitive strains of Gluconobacter. The gene, czcA, thought to encode the main pump protein of the efflux mechanism, was found in all Gluconobacter strains tested. However, amplification of a regulatory gene czcD, thought to sense the extracellular metal ion concentration, was not possible in the Gluconobacter strains tested. The PCR products were sequenced and analyzed for homology to the czc operon in Ralstonia. From the data gathered, it appears as though some strains of Gluconobacter contain at least a portion of the czc operon , encoding cadmium, cobalt and zinc resistance in Ralstonia eutropha. / Master of Science

Ralstonia solanacearum est une bactérie vasculaire d'origine tellurique dévastatrice chez les Solanacées maraîchères. L'une des difficultés pour la sélection variétale réside dans le contournement de la résistance, en raison de la grande variabilité et plasticité génotypique du pathogène. Trente accessions de tomate, aubergine et piment (Core-TEP) testées vis-à-vis de 12 souches représentatives des phylotypes I, II et III de R. solanacearum (Core-Rs2) ont été classées de très sensibles à très résistantes. Des groupes de souches définis en fonction de leur virulence et agressivité ont été nommés pathoprofils, d'une part, lorsque établis sur les 3 espèces et pathotypes, d'autre part, lorsque établis sur chacune des trois espèces. Aucune résistance universelle n'a pu être mise en évidence chez aucune des trois espèces. Le déterminisme génétique de la résistance à R. solanacearum chez l'aubergine a été étudié sur une population de lignées recombinantes F6 ainsi que sur les générations issues du croisement intraspécifique S. melongena MM738 (S) x AG91-25 (R), testées vis-à-vis de quatre souches du phylotype I. Une carte génétique composée de 119 marqueurs AFLP, SSR et SRAP, positionnés sur 18 groupes de liaisons, pour une longueur totale de 884 cM, a été construite. Les analyses génétiques montrent que la résistance aux souches CMR134, PSS366, GMI1000 est contrôlée par un même gène majeur expliquant jusqu’à 87% de la variance phénotypique. Celui-ci n'est pas détecté vis-à-vis de la souche virulente PSS4 qui contourne cette résistance. Dans ce cas, seul un QTL à effet intermédiaire expliquant jusqu’à 38 % de la variance phénotypique est trouvé sur un autre groupe de liaison. / The plant pathogenic soil-borne bacteria Ralstonia solanacearum causes heavy damage to solanaceous crops. One of the dilemmas for varietal breeding of solanaceous crops is the circumvention of the resistance to R. solanacearum due to the genotypic variability and plasticity of this pathogen. Thirty accessions of Tomato, Eggplant, and Pepper (Core-TEP), screened with a collection of 12 representatives strains of R. solanacearum phylotype I, II and III (Core-Rs2) within the species complex ranked from highly resistant to highly susceptible. The strains were grouped according to there profile of virulence on all three solanaceous, and by considering each species individually. We refer to these groups respectively, as pathoprofiles and pathotypes. No universal resistance was found for the three host species. Genetic analysis of resistance to R. solanacearum in eggplant was conducted against four strains of phylotype I. We used a population of recombinant lines F6 as well as the generations derived from the intraspecific cross between S. melongena MM738 (S) and AG91-25 (R). A genetic map was built with 119 markers a combination of AFLPs, SSRs and SRAPs positioned on 18 linkage groups, for a total length of 884 cM. The genetic analysis revealed that resistance to strains CMR134, PSS366, and GMI1000 was controlled by one single major gene, which explained up to 87% of the phenotypic variation. When the resistance against the highly virulent PSS4 strain is tested, this gene is not detected. In this case, a significant QTL with intermediate effect that explains up to 38% of phenotypic variation was found on another linkage group for this strain.

Le modèle étudié est l’agent phytopathogène vasculaire Ralstonia solanacearum, en portant une attention particulière aux souches de phylotype II. Cette bactérie d’origine tellurique est très diversifiée, tant au plan génétique que phénotypique. Sa classification en constante évolution témoigne d’une volonté de clarifier cette biodiversité inhabituellement forte, tout en cherchant à reconnaître les écotypes structurant ce complexe d’espèces, i.e., des groupes de souches partageant à la fois des traits génotypiques et biologiques spécifiques. Dans le cadre de ce pathosystème modèle, nous nous sommes attachés dans un premier temps à revisiter de façon précise les pathotypes au sein d’écotypes bien décrits dans la littérature, ou à en faire la description (phylotype III africain). Nous avons observé une forte convergence phénotypique entre les souches de phylotype III des hauts plateaux africains et les souches Brown rot de phylotype IIB-1, capables de flétrir la pomme de terre et d’autres Solanacées à température froide. L’adaptation de souches aussi diverses pour la tolérance au froid nous a conduits à dresser un bilan de la situation R. solanacearum en Europe et in extenso dans le bassin méditerranéen. Cette approche a permis d’apprécier les degrés de divergence significative dans le pouvoir pathogène (virulence et agressivité) sur Solanaceae au sein de souches quasi clonales unifiant l’écotype Brown rot, qui s’établissent aussi sous forme d’infections latentes dans les tissus vasculaires de bananiers (Musacées). Dans le même temps, le phénotype de souches pathogènes du bananier, unifiant l’écotype Moko, a aussi été revisité sur Solanaceae qu’elles parviennent à flétrir, y compris des ressources génétiques résistantes au flétrissement bactérien. L’ensemble de ces données expérimentales a permis de dégager les critères de sélection pour le choix de trois nouvelles souches du complexe d’espèces R. solanacearum, dont nous avons obtenu les séquences génomiques. Notre approche en génomique comparative a permis de décrire le premier pangénome chez cet agent pathogène : l’ensemble les gènes repérés de l’espèce. Ces données ont été exploitées par différentes approches bio-informatiques et permettent de concevoir une refonte pertinente du complexe d’espèces R. solanacearum en trois nouvelles espèces génomiques, regroupant les souches de phylotypes I (Asie) et III (Afrique) d’une part, puis les souches de phylotype II (Amérique), et enfin les souches de phylotype IV (Indonésie) d’autre part. Ce pangénome a ensuite été exploité en concevant et développant une puce à ADN, un outil permettant l’exploration à haut débit d’une grande quantité de souches. La densité des données expérimentales accumulées permet une démarche vers l’écologie moléculaire et de reconstituer certains pans du passé évolutif des souches de phylotype II chez R. solanacearum. Par ailleurs, l’analyse approfondie de ces données de génomique, associant phylogéographie et structuration des populations de l’écotype Brown rot, montre une double situation épidémiologique en Europe, recoupant des influences andines et africaines. De la même façon, l’écotype Moko présente trois structures génétiques distinctes. Ces données ont été analysées de manière à retracer les principaux flux de gènes dans les états ancestraux des phylotypes et de dégager la forte contribution de la partie mobile du génome, des gènes relatifs à l’adaptation environnementale et à la pathogénie, comme moteurs dans l’évolution de cet important organisme phytopathogène. / The studied model is the vascular plant pathogen Ralstonia solanacearum, with a particular focus on phylotype II strains. This telluric bacterium has a wide diversity, both on genotypic and phenotypic levels. Its evolving classification reflects the need to clarify its unusual biodiversity and seek to identify ecotype structure in this species complex, i.e., groups of strains with both genotypic and specific biological traits. Within the framework of this model pathosystem, we initially focused on deeply revisiting pathotypes among ecotypes, although well described in the literature, or describing new ecotypes (African phylotype III). We observed high phenotypic convergence between strains from phylotype III from the African highlands and Brown rot strains from phylotype IIB-1, both able to trigger wilt symptoms on potato and other Solanaceae at cold temperatures. Adaptation of diverse strains for cold tolerance led us to investigate the R. solanacearum situation in Europe and more specifically in the Mediterranean regions. This strategy allowed us to appreciate the significant divergence towards pathogenicity (virulence and aggressiveness) on Solanaceae within clonal-like structure of strains in the Brown rot ecotype, which also established latent interactions in the banana vascular system. In the mean time, phenotypes of banana pathogenic strains unifying the Moko ecotype, was also revisited on Solanaceae, and was able to trigger symptoms on both susceptible and resistant genetic resources to bacterial wilt. All these experimental data yielded selection criteria for choosing three new candidate strains in the R. solanacearum species complex for complete genome sequencing. Our genomic comparative approach allowed us to describe the first pangenome of this pathogen: all targeted identified genes of this species complex. These data were analyzed by various bioinformatic approaches and allowed us to design a complete reshaping of R. solanacearum species complex into three distinct genomic species, firstly clustering strains from phylotype I (Asia) with strains from phylotype III (Africa); strains from phylotype II (America); and lastly, strains from phylotype IV (Indonesia). This pangenome was then used for designing a DNA microarray, a high resolution tool that allowed us to explore a wide set of genomes. The density of accumulated data allowed for a molecular ecological approach to retrieve a certain amount of the evolutionary past of R. solanacearum phylotype II strains. Furthermore, a deeper analysis of these genomic data, combining phylogeography with population structure analysis of the Brown rot ecotype, revealed a dual epidemic situation in Europe, both across Andean and African influences. Similarly, the Moko ecotype presents three distinct genetic structures. These data were analyzed within the purpose of tracking the main gene flows in the ancestral states of phylotypes and to unravel the strong contribution of the mobile elements, genes related to environmental adaptation, and pathogenicity as a major driving force into the evolution of this successful plant pathogen.

O tomateiro (Solanum lycopersicum L.) é uma das plantas cultivadas de maior importância no mundo, sendo uma das principais hortaliças em importância econômica no Brasil. A murcha-bacteriana é uma doença dentre as mais limitantes para a cultura do tomateiro e o uso de cultivares resistentes à Ralstonia spp. é uma das únicas alternativas para evitar as perdas causadas por esse patógeno. Contudo, existem raríssimos estudos sobre a base genética de genótipos resistentes aos principais isolados de Ralstonia spp. Objetivou-se nesse trabalho estudar parâmetros genéticos da resistência à murcha-bacteriana em linhagens e híbridos usados como porta-enxertos de tomateiro, por meio de abordagens complementares que envolvem desde o ajuste das metodologias para indução artificial da doença, até estimativas das capacidades de combinação e a heterose entre linhagens, visando identificar cruzamentos promissores para o estabelecimento de um programa de melhoramento genético para resistência à murcha-bacteriana em tomateiro para porta-enxertos. Comparando-se quatro métodos de indução da resistência verificou-se que o método da lesão das raízes do torrão com objeto cortante (bisturi) e pulverização de 5 mL da suspensão bacteriana no torrão, comparativamente aos outros métodos avaliados, apresenta fácil execução, requer quantidades reduzidas de suspensão bacteriana e proporciona boas quantidades de plantas de tomateiro com sintomas de murcha-bacteriana, sendo o mais adequado entre os métodos testados. Foi estimada a heterose e capacidade de combinação entre linhagens de tomateiro para um isolado do biovar 2 de Ralstonia solanacearum em estágio de plântulas, em ambiente protegido, e em um solo naturalmente infestado por Ralstonia spp. Entre as linhagens avaliadas, apenas o genótipo Hawaii 7996 apresentou níveis aceitáveis de resistência, sendo necessário encontrar novas fontes de resistência para o início de um programa de melhoramento. Verificou-se que nenhuma das progênies derivadas dos cruzamentos desse estudo apresentaram resistência superior ao parental superior Além disso, foi verificada a importância dos efeitos aditivos e, consequentemente, os cruzamentos de genitores com alta CGC para o caráter e a seleção recorrente seriam as melhores alternativas no melhoramento para resistência à murcha-bacteriana. Finalmente, foram estudados os genitores e seus híbridos, utilizados como porta-enxerto em condições de campo e em ambiente protegido visando o aumento da resistência à murcha-bacteriana causada por Ralstonia spp., e incremento dos parâmetros produtivos de um híbrido comercial utilizado como copa. Verificou-se influência dos diferentes porta-enxertos em caracteres de produção e massa dos frutos e no desenvimento de copa. Caracteres relacionados ao sistema radicular dos porta-enxertos apresentaram heterose em relação aos seus genitores, com efeitos aditivos e não aditivos importantes, mostrando o desempenho das linhagens e sua contribuição para a produção de híbridos superiores. Por fim, este estudo possibilitou o melhor entendimento sobre a base genética da resistência em genótipos de tomateiro que possuem uso potencial como porta-enxertos resistentes à murcha-bacteriana. / The tomato (Solanum lycopersicum L.) is one of the most important cultivated plants in the world, being one of the main vegetables of economic importance in Brazil. The bacterial wilt is one of the most limiting diseases for the tomato crop and the use of resistant cultivars to Ralstonia spp. is one of the only alternatives to avoid losses caused by this pathogen. However, there are very few studies on the genetic basis of genotypes resistant to the main isolates of Ralstonia spp. The objective of this work was to study the genetic parameters of resistance to bacterial wilt in lines and hybrids used as tomato rootstocks, through complementary approaches that range from the adjustment of the methodologies for artificial induction of the disease, to estimates of the combining abilities and heterosis among lines, aiming to identify promising crosses for the establishment of a rootstock genetic breeding program for resistance to bacterial wilt in tomatoes. Comparing four resistance induction methods, it was verified that the method of injuring roots with cutting object (scalpel) and spraying 5 mL of the bacterial suspension in the clod compared to the other\'s methods evaluated, is easiest to perform, requires less amounts of bacterial suspension and provides good amounts of tomato plants with wilt symptoms, being the most suitable among the methods tested. The heterosis and combining ability of tomato lines for a strain of biovar 2 of Ralstonia solanacearum in greenhouse at seedling stage and in soil naturally infested by Ralstonia spp were estimated. Among the lines evaluated, only the Hawaii 7996 genotype showed acceptable levels of resistance, and it is necessary to find new sources of resistance for the beginning of a breeding program. It was verified that none of the progenies derived from the crosses of this study presented superior resistance to the superior parental. In addition, the importance of the additive effects was verified and, consequently, the crossings of parents with high CGC for the character and the recurrent selection would be the best alternatives in the improvement for resistance to bacterial wilt. Finally, we studied the parents and their hybrids, used as rootstocks under field conditions and in a protected environment aiming the increasing resistance to bacterial wilt caused by Ralstonia spp., and increasing of the yield parameters of a commercial hybrid used as a scion. The influence of the different rootstocks was verified in characters of yield and mass of the fruits and in the development of the scion. Characteristics related to the root system of rootstocks showed heterosis in relation to their parents, with important additive and non-additive effects, showing the performance of the lines and their contribution to the production of superior hybrids. Finally, this study allowed a better understanding of the genetic basis of resistance in tomato genotypes that have potential use as bacterial wilt resistant rootstocks.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-12-04T18:41:29Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação_final_Adenilson.pdf: 1632453 bytes, checksum: ca3bab925a332585e719109a07462e72 (MD5) / Made available in DSpace on 2018-12-04T18:41:29Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação_final_Adenilson.pdf: 1632453 bytes, checksum: ca3bab925a332585e719109a07462e72 (MD5) Previous issue date: 2018-09-27 / Os objetivos deste trabalho foram a obtenção de um mapa genético de alta densidade utilizando marcadores SNP (Single Nucleotide Polymorphism) obtidos através de genotipagem por sequenciamento (GBS) e identificar as regiões genômicas ligadas à tolerância à murcha bacteriana (Ralstonia solanacearum Smith) em uma população de duplo-haploides (DH) de tabaco. As linhagens endogâmicas NC95 (tolerante) e NC2326 (suscetível) foram cruzadas entre si gerando a população F1, anteras foram coletadas destas plantas para produção de haploides e posterior duplicação cromossômica através da cultura de anteras, gerando 180 famílias duplo-haploides que foram avaliadas em ambiente controlado quanto à tolerância à murcha bacteriana, após inoculação com R. solanacearum, através de uma escala de notas com amplitude de 0 a 4. As famílias DH foram genotipadas utilizando a metodologia de GBS e os dados resultantes desta genotipagem foram alinhados com o genoma de referência do tabaco para posterior obtenção dos marcadores SNP utilizados na construção do mapa de ligação. O mapa de ligação juntamente com os dados de fenotipagem foram utilizados para realizar o mapeamento de QTLs através do mapeamento por intervalo composto. Foram identificados 6.842 SNPs, utilizados para construção de um mapa de ligação com 70.583 cM, sendo este o maior mapa de ligação utilizando marcadores SNP disponível para tabaco e com o maior número de marcadores. Utilizando este mapa de ligação foram mapeados 13 QTLs para tolerância à murcha bacteriana em oito grupos de ligação, dos quais oito QTLs ainda não tinham sido identificados na literatura especializada. Os locos presentes nos grupos de ligação 3, 17 e 22 apresentaram os maiores efeitos na variação fenotípica. O elevado número de QTLs mapeados nesta população confirma o padrão de herança quantitativa da tolerância de tabaco à murcha bacteriana causada por R. solanacearum. / The objectives of this work were to obtain a high-density genetic map using SNP (Single Nucleotide Polymorphism) markers obtained through Genotyping-by-Sequencing (GBS) and to identify the genomic regions linked to bacterial wilt tolerance (Ralstonia solanacearum Smith) in a tobacco double-haploid (DH) population. The inbred lines NC95 (tolerant) and NC2326 (susceptible) were crossed generating the F1 population, anthers were collected from these plants for haploid production and subsequent chromosomic duplication using anthers culture, generating 180 double-haploid families that were evaluated in a controlled environment for tolerance to bacterial wilt after inoculation with R. solanacearum, using an assessment scale from 0 to 4. The DH families were genotyped using the GBS methodology and the resulting data from this genotyping were aligned with the reference genome and then to obtain the SNP markers used to construct the genetic linkage map. The linkage map jointly with the phenotyping data were used to QTL mapping through the composite interval mapping method. A total of 6,842 SNPs was identified and used to construct a linkage map with 70,583 cM, being the largest SNP-based genetic linkage map available for tobacco and presenting the highest number of markers. Using this linkage map, 13 QTLs were mapped for bacterial wilt tolerance in eight linkage groups, from those eight QTLs had not yet been identified in the specialized literature. The loci present in linkage groups 3, 17 and 22 had the highest effects on phenotypic variation. The high number of QTLs mapped in this population confirms the quantitative genetic control of tobacco tolerance to bacterial wilt caused by R. solanacearum.

O tomateiro (Solanum lycopersicum L.) é uma das plantas cultivadas de maior importância no mundo, sendo uma das principais hortaliças em importância econômica no Brasil. A murcha-bacteriana é uma doença dentre as mais limitantes para a cultura do tomateiro e o uso de cultivares resistentes à Ralstonia spp. é uma das únicas alternativas para evitar as perdas causadas por esse patógeno. Contudo, existem raríssimos estudos sobre a base genética de genótipos resistentes aos principais isolados de Ralstonia spp. Objetivou-se nesse trabalho estudar parâmetros genéticos da resistência à murcha-bacteriana em linhagens e híbridos usados como porta-enxertos de tomateiro, por meio de abordagens complementares que envolvem desde o ajuste das metodologias para indução artificial da doença, até estimativas das capacidades de combinação e a heterose entre linhagens, visando identificar cruzamentos promissores para o estabelecimento de um programa de melhoramento genético para resistência à murcha-bacteriana em tomateiro para porta-enxertos. Comparando-se quatro métodos de indução da resistência verificou-se que o método da lesão das raízes do torrão com objeto cortante (bisturi) e pulverização de 5 mL da suspensão bacteriana no torrão, comparativamente aos outros métodos avaliados, apresenta fácil execução, requer quantidades reduzidas de suspensão bacteriana e proporciona boas quantidades de plantas de tomateiro com sintomas de murcha-bacteriana, sendo o mais adequado entre os métodos testados. Foi estimada a heterose e capacidade de combinação entre linhagens de tomateiro para um isolado do biovar 2 de Ralstonia solanacearum em estágio de plântulas, em ambiente protegido, e em um solo naturalmente infestado por Ralstonia spp. Entre as linhagens avaliadas, apenas o genótipo Hawaii 7996 apresentou níveis aceitáveis de resistência, sendo necessário encontrar novas fontes de resistência para o início de um programa de melhoramento. Verificou-se que nenhuma das progênies derivadas dos cruzamentos desse estudo apresentaram resistência superior ao parental superior Além disso, foi verificada a importância dos efeitos aditivos e, consequentemente, os cruzamentos de genitores com alta CGC para o caráter e a seleção recorrente seriam as melhores alternativas no melhoramento para resistência à murcha-bacteriana. Finalmente, foram estudados os genitores e seus híbridos, utilizados como porta-enxerto em condições de campo e em ambiente protegido visando o aumento da resistência à murcha-bacteriana causada por Ralstonia spp., e incremento dos parâmetros produtivos de um híbrido comercial utilizado como copa. Verificou-se influência dos diferentes porta-enxertos em caracteres de produção e massa dos frutos e no desenvimento de copa. Caracteres relacionados ao sistema radicular dos porta-enxertos apresentaram heterose em relação aos seus genitores, com efeitos aditivos e não aditivos importantes, mostrando o desempenho das linhagens e sua contribuição para a produção de híbridos superiores. Por fim, este estudo possibilitou o melhor entendimento sobre a base genética da resistência em genótipos de tomateiro que possuem uso potencial como porta-enxertos resistentes à murcha-bacteriana. / The tomato (Solanum lycopersicum L.) is one of the most important cultivated plants in the world, being one of the main vegetables of economic importance in Brazil. The bacterial wilt is one of the most limiting diseases for the tomato crop and the use of resistant cultivars to Ralstonia spp. is one of the only alternatives to avoid losses caused by this pathogen. However, there are very few studies on the genetic basis of genotypes resistant to the main isolates of Ralstonia spp. The objective of this work was to study the genetic parameters of resistance to bacterial wilt in lines and hybrids used as tomato rootstocks, through complementary approaches that range from the adjustment of the methodologies for artificial induction of the disease, to estimates of the combining abilities and heterosis among lines, aiming to identify promising crosses for the establishment of a rootstock genetic breeding program for resistance to bacterial wilt in tomatoes. Comparing four resistance induction methods, it was verified that the method of injuring roots with cutting object (scalpel) and spraying 5 mL of the bacterial suspension in the clod compared to the other\'s methods evaluated, is easiest to perform, requires less amounts of bacterial suspension and provides good amounts of tomato plants with wilt symptoms, being the most suitable among the methods tested. The heterosis and combining ability of tomato lines for a strain of biovar 2 of Ralstonia solanacearum in greenhouse at seedling stage and in soil naturally infested by Ralstonia spp were estimated. Among the lines evaluated, only the Hawaii 7996 genotype showed acceptable levels of resistance, and it is necessary to find new sources of resistance for the beginning of a breeding program. It was verified that none of the progenies derived from the crosses of this study presented superior resistance to the superior parental. In addition, the importance of the additive effects was verified and, consequently, the crossings of parents with high CGC for the character and the recurrent selection would be the best alternatives in the improvement for resistance to bacterial wilt. Finally, we studied the parents and their hybrids, used as rootstocks under field conditions and in a protected environment aiming the increasing resistance to bacterial wilt caused by Ralstonia spp., and increasing of the yield parameters of a commercial hybrid used as a scion. The influence of the different rootstocks was verified in characters of yield and mass of the fruits and in the development of the scion. Characteristics related to the root system of rootstocks showed heterosis in relation to their parents, with important additive and non-additive effects, showing the performance of the lines and their contribution to the production of superior hybrids. Finally, this study allowed a better understanding of the genetic basis of resistance in tomato genotypes that have potential use as bacterial wilt resistant rootstocks.

Made available in DSpace on 2016-04-28T14:57:35Z (GMT). No. of bitstreams: 1 Ana Rosa de Figueiredo Fernandes.pdf: 5291957 bytes, checksum: e9ba6c76361eb4a2e901846a5bb5c2dd (MD5) Previous issue date: 2009-10-29 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / ?The pathogenicity of Pratylenchus brachyurus on tobacco (Nicotiana tabacum) cultivar K326 was evaluated in experiments testing different initial population densities of the nematode (Pi = 0; 1,000; 3,000; 9,000 and 27,000 eggs and larvae per plant), in eight replications. The isolate was monoxenically multiplied on carrot discs. At the end of the experiment (70 days after inoculation), the above ground part of each plant was weighed and measured and, the respective root system was processed. The reproduction rate of Pratylenchus brachyurus was estimated by extracting the nematodes of the roots and of the soil. Necroses on the roots of the tobacco plants were observed. Pratylenchus brachyurus caused well-delimited root lesions on tobacco root. None of the analyzed plants died; however plant growth was reduced. Also, it was observed a decrease of the fresh mass of roots and of the dry top weight, mainly under the highest population density (27,000 nematodes per plant). The reproduction rate was low. Besides the interaction between Pratylenchus brachyurus and Ralstonia solanacearum in two tobacco varieties, Virg?nia K326 and Burley By21 was evaluated. Test plants were inoculated with the nematode in the initial population density of 3,000 individuals (eggs and larvae) by plant and, 15 days later, the plants were inoculated with a sample of soil infested by the bacterium, in estimated population density of 106 CFU.g-1 of soil. Besides the mixed inoculation with Pratylenchus brachyurus and Ralstonia solanacearum, tobacco plants were single inoculated. The plants were monitored daily. Dates of the beginning of symptom expression were registered, as well as symptom evolution. When the plants were inoculated with Pratylenchus brachyurus and Ralstonia solanacearum, symptom of wilt that is caused by the bacterium Ralstonia solanacearum began earlier than in single inoculated plants, and they also evolved quicker, inclusive in the variety Virg?nia K326 that was considered more tolerant. In this case, the presence of Pratylenchus brachyurus, in the root system of these plants, probably favored the infection by Ralstonia solanacearum, even before the symptoms caused by the nematodes could be detected. This study was done in greenhouse and under laboratory conditions. / ?A patogenicidade de Pratylenchus brachyurus em fumo Virg?nia K326 foi avaliada em experimento no qual foram testadas diferentes densidades populacionais iniciais do nemat?ide (Pi = 0; 1.000; 3.000; 9.000 e 27.000 ovos e larvas por planta), em oito repeti??es. O isolado foi multiplicado axenicamente em discos de cenoura. Ao final do experimento (85 dias), as plantas tiveram sua parte a?rea pesada e medida e foi processado o sistema radicular de cada uma. O fator de reprodu??o foi estimado por extra??o dos nemat?ides das ra?zes e do solo. Necroses nas ra?zes das plantas foram observadas. Pratylenchus brachyurus causou les?es radiculares delimitadas nas ra?zes de fumo. N?o houve morte de nenhuma planta analisada, por?m a altura das plantas foi afetada e tamb?m a massa seca da parte a?rea, principalmente sob a densidade populacional mais alta, de 27.000 nemat?ides por planta. O fator de reprodu??o foi baixo. Al?m disto, avaliou-se a intera??o entre Pratylenchus brachyurus e Ralstonia solanacearum em fumo Virg?nia variedade K326 e fumo Burley variedade BY21. As plantas foram inicialmente inoculadas com o nemat?ide na densidade populacional de 3.000 ovos e larvas por planta e 15 dias ap?s, foram inoculadas com uma amostra de solo infestado pela bact?ria, na densidade populacional estimada de 106 UFC.g-1 de solo. Al?m da inocula??o mista com Pratylenchus brachyurus e Ralstonia solanacearum, testemunhas foram inoculadas isoladamente. As plantas foram monitoradas diariamente, anotando-se a data de in?cio e da evolu??o dos sintomas. Quando as plantas foram inoculadas com os Pratylenchus brachyurus e Ralstonia solanacearum, os sintomas de murcha, que s?o causados pela bact?ria se manifestaram mais cedo e tamb?m evolu?ram mais r?pido, inclusive na variedade K326 que foi considerada mais tolerante. Neste caso, provavelmente a presen?a de Pratylenchus brachyurus, no sistema radicular dessas plantas, favoreceu a infec??o por Ralstonia solanacearum, antes mesmo que os sintomas causados pelo nemat?ide pudessem ser observados. Este trabalho foi realizado em casa de vegeta??o e em laborat?rio.