Fusarium oxysporum is a ubiquitous soil-borne fungus that includes pathogenic and non-pathogenic members. The pathogenic members are best known for causing Fusarium wilt diseases of many economically important agricultural crops. One such a crop is banana (Musa spp.), which is affected by a special form of the fungus known as F. oxysporum f.sp. cubense (Foc). Fusarium wilt was responsible for devastating losses of Gros Michel export bananas in Central America during the first half of the 20th century, and is now, once again, threatening world banana production that is primarily based on the sweet Cavendish varieties, both in the tropics and subtropics. To effectively manage Fusarium wilt, adequate knowledge of the pathogen, plant and environment is required. With this thesis I hope to contribute to the current knowledge available on the pathogen. Previous studies investigated the phenotypic and genotypic diversity, the spread and distribution, and the phylogeny of Foc. Some aspects related to the biology, physiology, diversity and pathogenicity of Foc, however, appeared to be unresolved. These aspects are important in order to develop a sustainable management strategy for Fusarium wilt to ensure continued banana production. Chapter 1 depicts a general review on F. oxysporum as the causal agent of Fusarium wilt of various fundamental crops, and gives a broad overview of the biology, taxonomy, physiology and pathogenicity of the pathogen. Through the application of modern molecular genetic techniques, a lot of progress has been made in the identification of genes and processes involved in the biology and pathogenesis of Fusarium wilt pathogens. The review concludes that some work, however, still needs to be conducted before topics such as race designation and pathogenesis in Foc are fully understood. Temperature, pH and nutrition are all factors contributing to the pathogenesis of F. oxysporum. The different factors can either favour or suppress the pathogen, or they can have a stimulating or inhibiting effect on the host plant. In Chapter 2 the pathogenicity and phenotypic characteristics of a genotypically uniform population of Foc was investigated. Physiological studies included determining the minimum, maximum and optimum temperatures and pH at which Foc grows in vitro, and what nitrogen sources stimulate and inhibit growth of Foc. Knowledge on these aspects could contribute to the management of the pathogen in the field. Differentiation among species of Fusarium can be problematic. To resolve questions related to the nomenclature in Fusarium, our research focus has shifted to the use of molecular tools for identification and determination of evolutionary relationships among and within species. In the past, phylogenetic studies on Foc were conducted using molecular tools such as sequencing, Restriction Fragment Length Polymorphisms, Random Amplified Polymorhic DNA and DNA Amplification Fingerprinting, with varying amounts of success. In Chapter 3 the usefulness of Amplified Fragment Length Polymorhism (AFLP) analysis to study diversity inFoc isolates was investigated. Of the 21 vegetative compatibility groups (VCGs) of Foc identified around the world, only VCG 0120 is found in South Africa. Chapter 4 aimed to identify an AFLP polymorphic DNA fragment unique to VCG 0120, and to develop a molecular marker of this fragment. Such a marker would be extremely valuable to distinguish between VCG 0120 and other isolates of F. oxysporum in terms of identification and confirmation of Fusarium wilt of banana in South Africa. Several pathogenicity-related genes have been identified in F. oxysporum. In Chapter 5, the presence of three pathogenicity-related genes (fmk1, pg1 and xyl3) in F. oxysporum isolates pathogenic and non-pathogenic to banana were verified by means of PCR amplification. The value of pathogenicity genes such as fmk1 and pg1 in comparative phylogenetic analysis was further substantiated. / Dissertation (MSc (Microbiology))--University of Pretoria, 2007. / Microbiology and Plant Pathology / unrestricted

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-02-17T12:44:24Z No. of bitstreams: 1 Andre Luiz Menezes Machado.pdf: 1193901 bytes, checksum: 3958c2853de30c17420bd30e2a594162 (MD5) / Made available in DSpace on 2017-02-17T12:44:24Z (GMT). No. of bitstreams: 1 Andre Luiz Menezes Machado.pdf: 1193901 bytes, checksum: 3958c2853de30c17420bd30e2a594162 (MD5) Previous issue date: 2012-07-05 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Tomato (Lycopersicon esculentum) crop yield has been limited by Fusarium wilt occurrence in the State of Pernambuco, Brazil. This disease, caused by Fusarium oxysporum f.sp. lycopersici, drastically reduces the harvest period due to the early fruit fall. This work aimed to analyze the intensity of Fusarium wilt in tomato planted in 47 soil samples from the Agreste region of Pernambuco and to determine factors which could be related to either soil suppressivenes or conduciveness to this disease/pathogen. Bioassays were carried out using tomato (Santa Clara cv.) planted in artificially infested and non-infested soils, aiming to verify the existence of suppressive and conducive soils to the disease. In order to characterize factors which could be related to these phenomena, the samples were submitted to analysis for determination of field capacity, permanent wilting point, clay, silt and sand percentages (physical characteristics), macronutrients, microbialcarbon, carbon from organic matter and total nitrogen levels (chemical characteristics) and population levels of Fusarium oxysporum, Trichoderma spp., Bacillus spp. and Pseudomonas spp. of fluorescent group in the soils (microbiological characteristics). Then the influence of these factors upon each other as well as on the incidence of the disease was verified. Fusarium wilt was positively correlated (r = 0,32) to soil C/N ratio in the first bioassay, however the disease was negatively correlated (r = -0,35) to Ca level in the soil, for the second one, both artificially infested with the pathogen. CAF-1 and CAF-16 samples were considered suppresive, while CAF-2 and SAI-2 were conducive. Infested and non-infested bioassays were related to each other pointing out the occurrence of suppressiveness in the soils No significant correlations (P=0,05) between disease levelsand physical, chemical or microbiological soil characteristics were observed. Furtherstudies must be carried out to characterize soils suppressiveness and conduciveness to Fusarium wilt of tomato in the Agreste region, in order to effectivelly contribute for the development of an integrated disease management / No Estado de Pernambuco, a produtividade da cultura do tomateiro (Lycopersicon esculentum) tem sido limitada devido à ocorrência da murcha-de-fusário, causada por Fusarium oxysporum f.sp. lycopersici, que reduz drasticamente o período de colheita pela queda prematura dos frutos. O presente trabalho teve como objetivos analisar a intensidade da murcha-de-fusário em plantas de tomateiro cultivadas em 47 amostras de solos da região Agreste de Pernambuco e determinar os possíveis fatores associados à supressividade ou conducividade desses solos à doença. Foram realizados bioensaios com plantas de tomateiro (cv. Santa Clara) cultivadas nos solos com e sem infestação artificial com o patógeno, sendo constatada a existência de solos supressivos e conducivos à doença. Visando caracterizar os possíveis fatores envolvidos nesses fenômenos, os solos foram submetidos a análises para determinação das características físicas (capacidade de campo,ponto de murcha permanente e teores de areia, silte e argila), químicas (quantificação de macronutrientes, carbono microbiano, carbono orgânico total e nitrogêncio total) e microbiológicas (levantamento populacional de Fusarium oxysporum, Trichoderma spp., Bacillus spp. e Pseudomonas spp. do grupo fluorescentes). Foi analisada a interrelação entre os fatores e a influência sobre a supressividade e/ou conducividade desses solos à murcha-de-fusário. A incidência da doença se correlacionou positivamente (r = 0,32) com a relação C/N, no primeiro plantio, e negativamente (r = -0,35) com os teores de Ca no solo, no segundo plantio, ambos com infestção artificial. Os solos CAF-1 e CAF-16 foram considerados supressivos, enquano CAF-2 e SAI-2 foram conducivos. Os plantios com esem infestação correlacionaram-se, indicando a supressividade nos solos analisados. Não foram constatadas correlações significativas (P=0,05) dos níveis de doença com as demaiscaracterísticas químicas, físicas e microbiológicas dos solos. Novos estudos devem ser realizados para a caracterização dos mecanismos de supressividade ou conducividade dos solos da região Agreste à murcha-de-fusário do tomateiro, visando contribuir efetivamente para o manejo integrado da doença

Made available in DSpace on 2014-06-12T15:50:48Z (GMT). No. of bitstreams: 1 license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2009 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Lectinas são proteínas que se ligam a carboidratos e glicoconjugados. Rizomas de Microgramma vaccinifolia têm ampla utilização na medicina popular no tratamento de hemoptises e hematúria. Os objetivos deste trabalho foram isolar, caracterizar, avaliar as atividades tóxica, antibacteriana e antifúngica da lectina de rizoma de M. vaccinifolia (MvRL) e identificar as raças 1, 2 e 3 de Fusarium oxysporum f. sp. lycopersici por biologia molecular. As proteínas do extrato de rizoma (ER) foram fracionadas com sulfato de amônio fornecendo a fração 0-60% (F0-60%). Atividade hemaglutinante (AH) e concentração de proteína foram determinadas em ER e F0-60%. MvRL foi isolada por cromatografia da F0-60% em Sephadex G-25. A AH de MvRL foi avaliada em presença de carboidratos, glicoproteínas, preparações contendo carboidrato das raças 1, 2 e 3 de Fusarium oxysporum f. sp. lycopersici, em diferentes temperaturas, valores de pH e na presença de íons. Eletroforese em gel de poliacrilamida de MvRL foi realizada em condições nativas (PAGE) e desnaturadas (SDS-PAGE). O efeito de MvRL sobre Artemia salina, bactérias e fungos foi também avaliado. O DNA das raças 1, 2 e 3 de Fusarium oxysporum f. sp. lycopersici foi isolado utilizando marcadores moleculares ISSR e RAPD. MvRL aglutinou eritrócitos humanos e sua AH foi inibida por manose, soro fetal bovino e preparações de F. oxysporum f.sp. lycopersici. A AH de MvRL foi termoestável, ativa em pH 5,0 e dependente de íons. PAGE revelou MvRL como uma proteína ácida e SDS-PAGE revelou banda polipeptídica glicosilada de massa molecular 17 kDa. Cromatografia de gel filtração definiu a massa molecular nativa de MvRL como 100 kDa indicando a lectina como um agregado molecular. MvRL foi tóxica sobre A. salina (CL50 de 154,16 μg/mL), não exibiu atividade antibacteriana e apresentou atividade antifúngica. MvRL foi mais ativa em inibir o crescimento da raça 3 de F. oxysporum f.sp. lycopersici. Os marcadores moleculares foram adequados para avaliar a variabilidade genética das raças. Em conclusão MvRL é uma lectina com atividade antifúngica e o efeito sobre F. oxysporum f.sp. lycopersici foi diferente para as três raças

Fusarium oxysporum f.sp. cubense Schlecht (Foc), causal agent of Fusarium wilt of banana (Panama disease), is considered to be one of the most serious threats to banana production in the world. There is no effective control measure for Fusarium wilt, except for the replacement of susceptible with resistant banana varieties. However, resistant varieties are not always acceptable to producers and local consumer markets. A greater awareness of the detrimental effect of chemicals on the environment has stimulated research on biological control of plant pathogens. The use of indigenous microorganims, such as non-pathogenic F. oxysporum and the bacterium Pseudomonas fluorescens, therefore, offers not only an environmentally safe but also an economical approach to combat Fusarium wilt of banana as part of an integrated disease management strategy. Non-pathogenic F. oxysporum and P. fluorescens isolates have previously been isolated from the root rhizosphere in disease suppressive soils. These isolates have the ability to reduce the incidence of Fusarium wilt in greenhouse pathogenicity trials. In this study we had hoped to expand on existing knowledge on the biological control of Fusarium wilt of banana with non-pathogenic endophytic F. oxysporum and P. fluorescens. Isolates that significantly suppress disease development in greenhouse trials were tested under field conditions. Physiological and histological studies were also performed to understand the modes of action of putative biological control agents. For the histological investigations, non-pathogenic F. oxysporum isolates were modified with green and red fluorescent proteins. Chapter 1 depicts a general overview of the biological control of Fusarium wilt diseases of agricultural crops. This chapter addresses the biology and pathogenesis of F. oxysporum, before strategies to control Fusarium wilt are discussed. The application of biological control organisms was analysed in terms of potentially useful organisms, where they can be isolated, and their possible modes of action. Finally, factors that influence biological control of Fusarium wilt diseases are discussed. A good source of prospective biocontrol agents is suppressive soils. In Chapter 2, non-pathogenic F. oxysporum isolates were collected from healthy banana roots in disease suppressive soil. Random Fragment Length Polymorphisms of the intergenic spacer region were then applied to group the non-pathogenic F. oxysporum isolates into genotypes, from which candidates were selected for biological control studies. The selected endophytes were then inoculated onto banana roots to determine their ability to act as biocontrol agents against Foc. The isolates that protected banana best against Fusarium wilt in the greenhouse, together with P. fluorescens WCS 417, were tested in the field to determine whether these isolates could effectively reduce disease incidence in an uncontrolled environment. The ability of non-pathogenic F. oxysporum and P. fluorescens WCS 417 to induce systemic resistance in Cavendish banana plants against Foc was investigated in Chapter 3 with the use of a split-root technique. The putative biocontrol agents were inoculated, separately and in combination, on one half of the roots in a split-root experiment, while the other half was challenged by a pathogenic isolate of Foc. Five different phenolic acids were assayed which included total soluble phenolic acids, non-conjugated (free acids) phenolic acids, ester-bound phenolic acids, glycosidebound phenolic acids and cell wall-bound phenolic acids. The knowledge gained will contribute to the understanding of how the biocontrol agents may induce defense responses in banana roots against Foc. Non-pathogenic isolates of F. oxysporum were transformed with the green fluorescent protein (GFP) and DsRed-Express genes in Chapter 4. These isolates were used to visualise their interactions with a GFP-transformed Foc isolate on the banana root in a non-destructive manner by means of confocal laser scanning microscopy (CLSM) in Chapter 5. The ability of non-pathogenic F. oxysporum and P. fluorescens WCS 417 to induce structural changes was also investigated with a split-root system using the CLSM. Antibioses as a mode of action of the two potential biocontrol agents was tested in vitro. Understanding the modes of action of non-pathogenic F. oxysporum and P. fluorescens WCS 417 are important when considering strategies for the implementation of these isolates in an integrated disease management strategy against Fusarium wilt of banana. / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2011. / Microbiology and Plant Pathology / unrestricted

Fusarium wilt of banana has a long and devastating history in many of the world’s banana producing countries. The most pronounced damage caused by Fusarium oxysporum f.sp. cubense (Foc), the Fusarium wilt pathogen, occurred during the 20th century in Central America, where tens of thousands of virgin forests were lost to further banana production. No control strategy is effective against Fusarium wilt other than replacement of susceptible by resistant varieties. It is, therefore, important to develop or identify resistant replacements that would not only be able to resist the pathogen, but also be acceptable to consumers. Resistance in wild banana varieties has been identified, and hybrids have been developed by breeding programmes with good resistance to Fusarium wilt. These varieties, unfortunately, appear not to be acceptable replacements for Cavendish bananas, the sweet desert banana variety that serves as the primary export banana and constitutes almost 40% of all bananas planted in the world today. A field selection, GCTCV-218, now proved to be the Cavendish plant with the most resistance to Foc ‘tropical’ race 4 (VCG 0121) has saved the Cavendish-based banana industry in Taiwan from devastation. In this thesis, GCTCV-218 has been evaluated against Foc ‘subtropical’ race 4 (VCG 0120), the primary variant of the pathogen in subtropical banana-producing countries such as South Africa, Australia and the Canary Islands. Defence-associated genes that are differentially expressed and that were up-regulated early in the defence response against the pathogen were isolated and identified. Greenhouse and field trials conducted at the research facilities of the Forestry and Agricultural Biotechnology Institute, University of Pretoria and in Kiepersol, South Africa, respectively, showed that GCTCV-218 had a significantly higher level of disease tolerance against Foc ‘subtropical’ race 4 (VCG 0120) when compared to the commercially grown Williams cultivar. Phenolic assays revealed that total phenolics and cell-wall bound phenolics were expressed at higher levels in GCTCV-218 after pathogen attack and seemed to play an important role in the tolerance of GCTCV-218. It was, therefore, proposed that GCTCV-218 could be considered a replacement for other Cavendish banana varieties planted in South Africa. The genetic basis of defence mechanisms in banana to Foc is unknown. In this investigation, Suppression Subtractive Hybridisation (SSH) was used to construct a cDNA library, containing banana genes that were up-regulated early (3&6 hours after infection), in the GCTCV-218/Foc interaction. The efficiency of the procedure was confirmed by PCR amplification of a known defence gene (endochitinase) present in the subtracted tester material, as well as analysing the reduction of a known housekeeping gene, actin, in the subtracted material compared to unsubtracted material. Southern blot data further provided confidence in the subtraction process. A cDNA library containing 736 gene fragments was constructed and then subjected to a screening procedure to remove false positives that escaped the subtraction process. The screening of a banana cDNA library for defence-related genes involved the development of a high-throughput cDNA microarray technique. This novel technique removed all false positives, such as housekeeping genes that escaped the subtraction as well as clones representing rDNAs. Seventy-nine genes differentially expressed in GCTCV-218 and not in Williams were selected, sequenced and subjected to BLASTX, BLASTN and DBest searches. Of these, several gene fragments showed homology to defence-associated genes, and 20 unique genes fragments were identified. These include two different peroxidases, response regulator 6, catalase 2, metallothionein, pectin acetylesterase (PAE), two different unknown proteins, salt stress, trypsin inhibitor, unspecific monooxygenase cytochrome P450, Bowman Birk proteinase inhibitor, root control, xylanase inhibitor, inhibitor CII, hypothetical protein, putative senescence-associated protein, pathogenesis-related protein 1 (PR1) and ribosomal protein S3a. The significance of the defence reaction to Fusarium wilt diseases in agricultural crops depends on the tempo of plant response. When a host plant is able to respond early to pathogen invasion the pathogen is successfully contained, preventing further spread throughout the plant. The expression of genes with antimicrobial activity, such as endochitinase, suggests an induced biochemical defence response against Foc. The expression of PAE and PR1 results in the deposition of lignin and callose production for cell wall strengthening. Four defence associated genes (catalase 2, pectin acetyl esterase (PAE), PR-1 and endochitinase) were selected for expression profile analysis using Real-time reverse transcriptase PCR, with TaqMan® and Light Cycler technology. All four genes were shown to be differentially expressed in GCTCV-218 at 3 and 6 hrs after infection, confirming SSH results. PR-1 and PAE were induced very early (3 hrs after infection) in the GCTCV-218, while PR3 and catalase 2 followed with a significant induction at 6 hrs after infection. This study concludes that GCTCV-218 is able to respond rapidly in response to Foc infection by activating both a biochemical and structural defence mechanism. / Thesis (PhD (Plant Pathology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

Fusarium wilt of banana, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive plant diseases in recorded history. The disease was first discovered in Australia in 1874 but became renowned for the severe losses it caused to export banana plantations during the 1960s in Central America. The banana export industry was saved only by replacing Gros Michel bananas, the dessert banana grown for the export market, with highly resistant Cavendish banana cultivars. Despite this apparent solution, the fungus was found to attack Cavendish bananas in the sub-tropics, where plants were believed to be predisposed to the disease by the cool winter climate. Good management practices and conventional disease management strategies have not been sufficient to reduce losses and stop the disease from spreading, and today Fusarium wilt can be found in almost all banana-producing countries of the world. Since 1988, Foc has been responsible for significant losses of Cavendish bananas in tropical Asia. The only sustainable control measure, the use of resistant varieties, is not always popular as people prefer to eat locally adopted varieties that, unfortunately, are susceptible to Foc. Sustainable Fusarium wilt management in banana depends on the improvement of existing banana cultivars or the development of novel disease management strategies. Molecular biology and biotechnology provide opportunities to introduce foreign resistance genes into existing cultivars and to develop new, environmentally friendly products that can protect susceptible bananas from Foc. Better knowledge of the Fusarium wilt pathogen, its diversity, and its mechanisms of pathogenesis will contribute significantly to developing these novel approaches for control of the disease. Molecular information on the pathogenicity of Foc, however, is limited, whereas other formae speciales of F. oxysporum have been better studied. In this thesis, Agrobacterium tumefaciens-mediated transformation of (ATMT) was employed to investigate genes responsible for pathogenicity of Foc to banana. Chapter 1 provides an overview of pathogenicity in F. oxysporum. Pathogenic and non-pathogenic forms of the fungus are first introduced to the reader, and then the biology, epidemiology and etiology of pathogenic forms of F. oxysporum are discussed. The genetic make-up and ability of the Fusarium wilt fungus to cause disease in plants concludes the first part of the review. In recent years, there has been a noted increase in the number of techniques available to study hostpathogen interactions. The second part of the review concentrates on these techniques and their applications in studying pathogenicity of the Fusarium wilt pathogen. In Chapter 2, an ATMT and screening system for Foc was developed. Five A. tumefaciens strains were evaluated for their efficiency to transform Foc with a randomly integrating vector that confers hygromycin B resistance and expression of green fluorescent protein (GFP). A small insertion mutant library of Foc was created, and a subset of transformants was characterized by determining the number of T-DNA inserts present, the location and identity of predicted genes disrupted by T-DNA insertion, and whether transformants of Foc were altered in their virulence against susceptible banana plants. In Chapter 3, the role of a known pathogenicity gene, Frp1, of the tomato pathogen F. oxysporum f. sp. lycopersici (Fol) was investigated in Foc. The first objective was to isolate and characterize the Frp1 gene in Foc, and to compare it to the homologous gene in Fol. A vector containing a modified Fol Frp1 gene was then obtained and used for targeted disruption of the gene in Foc via ATMT. Mutants in which the Frp1 gene was disrupted were then analyzed for GFP expression, culture morphology, and alterations in pathogenicity to banana. / Dissertation (MSc)--University of Pretoria, 2008. / Microbiology and Plant Pathology / unrestricted

Allelopathy occurs when one organism releases a compound into the environment that affects the functioning of another organism. Scientists have long suspected that alleopathic plant compounds could offer novel, softer chemistries to the ongoing battle of controlling pests in agricultural fields. Strawberry growers rely on toxic fumigants to kill soilborne fungal pests, weeds, nematodes, and insects. Increased regulations have reduced the use of fumigants (including methyl bromide), and strawberry growers need new sustainable pest control solutions. We selected four putative allelochemicals with known fungicidal and herbicidal activity (ferulic acid, gallic acid, juglone, and p-Coumaric acid). We assessed the pesticidal activity of these plant compounds both in agar and in soil on two emerging soilborne fungal pathogens (Macrophomina phaseolina and Fusarium oxysporum f.sp. fragariae), and four annual weeds commonly found in strawberry production fields (Malva parviflora, Melilotus officinalis, Poa annua, and Senecio vulgaris). We also assayed lettuce (Lactuca sativa ‘Inferno’), which served as a positive control plant species due to its sensitivity to phytotoxic compounds. Fitted sigmoidal dose-response curves predicted EC50 and EC75 values for each combination of plant compound and pest. All plant compounds inhibited the in vitro radial mycelial growth of the two soilborne fungal pathogens in a dose-dependent manner. Fusarium oxysporum f.sp. fragariae was more sensitive to the plant compounds than Macrophomina phaseolina. Average EC50 values for the radial mycelial growth of two F. oxysporum f.sp. fragariae isolates were 75.1 parts per million by weight (ppmw) juglone, 469 ppmw p-Coumaric acid, and 687 ppmw ferulic acid. Average EC50 values for the radial mycelial growth of two M. phaseolina isolates were 196 ppmw juglone, 2869 ppmw p-Coumaric acid, and 5716 ppmw ferulic acid. The three compounds we assayed in vitro also reduced M. phaseolina colony forming unit counts in soil and the EC50 values were 476 ppmw ferulic acid, 612 ppmw juglone, and 827 ppmw p-Coumaric acid. Metconazole, the conventional fungicide control, did not inhibit M. phaseolina colony forming unit counts in soil at its label high rate. The plant compounds required similar or lower rates to inhibit colony forming units that grew from M. phaseolina overwintering structures (microsclerotia) in soil as to inhibit radial mycelial growth in vitro. Based on the EC50 value in soil assays, ferulic acid was the least expensive plant compound to apply on a per acre basis to inhibit M. phaseolina ($74,226). In F.oxysporum f.sp. fragariae soil assays, the compounds induced hormesis at lower rates and may be germination stimulant candidates. Metconazole and the high rates of every compound effectively or completely inhibited F. oxysporum f.sp. fragariae colony forming units in soil. The plant compounds were more herbicidal than fungicidal in vitro. When combining the in vitro seedling length results for L. sativa, M. parviflora, P. annua, and S. vulgaris the EC50 values differed significantly (p < .0001) and were: 47 ppmw juglone, 120 ppmw p-Coumaric acid, 189 ppmw ferulic acid, and 297 ppmw gallic acid. At least one rate of ferulic acid, juglone, and p-Coumaric acid inhibited the germination of all plant species, while gallic acid only inhibited the germination of P. annua at 1000 ppmw (p < .05). In soil, visible microbial contamination in individual wells of 24-well plates and seed dormancy made it difficult to fit curves to weed seedling length data. The soil assay L. sativa seedling length EC50 values 11 days after initial treatment were slightly higher than in vitro, although plant compounds were in the same order of phytotoxicity: 129 ppmw juglone, 616 ppmw p-Coumaric acid, 644 ppmw ferulic acid, and 1584 ppmw gallic acid. Based on the EC50 value in soil assays, the least expensive compound to inhibit L. sativa seedling length on a per acre basis was gallic acid ($21,676). Germination 26 days after initial soil treatment generally declined in a dose-dependent manner for each compound. There was a direct relationship between plant compound rate and seedling damage in soil with the higher rates of all compounds, except p-Coumaric acid, inducing damage comparable to a conventional herbicide (pendimethalin or oxyfluorfen). Contaminated treatments appeared to be due to an interaction between plant compounds and microorganisms because herbicide and water controls had almost no microbial growth 11 days after initial treatment. Further, there was a significant positive linear relationship between level of contamination in phenolic acid-treated wells (ferulic acid, gallic acid, and p-Coumaric acid, p < .0001) and the in soil rate. This relationship was slightly negative in juglone soil treatments (p = .0167), which may be due to its greater antimicrobial activity than the phenolic acids. We propose that herbicidal effects in soil were due to the joint effect of the plant compounds themselves, and the microbial growth in wells. Microbial growth was either antagonistic or additive to the inhibitory action of the plant compounds. The plant compounds we assayed were inhibitory of emerging fungal pathogens in strawberry production and common annual strawberry field weeds. Evidence presented in this thesis correlates well with past research that not only found plant compounds to be herbicidal and fungicidal, but also described their modes-of-action (such as the production of reactive oxygen species that causes necrotic lesions on roots, and inhibition of glycolytic enzyme activity that prevents germination), and implicate plant compounds as carbon sources for a variety of microorganisms. Compound prices are currently exorbitant, but may decline as demand increases. Whether or not they provide effective pest control may depend on soil texture, organic matter, microbial diversity, and other edaphic factors.

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-02-20T14:08:02Z No. of bitstreams: 1 Domingos Eduardo Guimaraes Tavares de Andrade.pdf: 2752116 bytes, checksum: f1548d1f41182d089565eefd683ee4ff (MD5) / Made available in DSpace on 2017-02-20T14:08:02Z (GMT). No. of bitstreams: 1 Domingos Eduardo Guimaraes Tavares de Andrade.pdf: 2752116 bytes, checksum: f1548d1f41182d089565eefd683ee4ff (MD5) Previous issue date: 1999-02-24 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Fresh tomato is very important in the Agreste Region of Pernambuco State, Brazil. However its production is impaired by the occurrence of Fusarium wilt caused by Fusarium oxysporum f.sp. lycopersyci. This study aimed to survey the disease intensity in planting areas of Camocim de São Félix county, Agreste of Pernambuco and to determine the ideal sample size for disease assessment, to analyze the disease spatial pattern in field, to characterize the variability of Fusarium oxysporum f.sp. lycopersyci populations and to select the resistance of tomato cultivars to races 1 and 2 of the pathogen. The disease survey in 50 planting areas showed high disease prevalence (72%) and average incidence of 17,15%. Using the incidence data from 36 areas as pilot-samples, the sample size for disease assessment was determined accordimg to the mean variability coefficient. The number of rows to be sampled was inversely related to disease incidence and acceptable error. To quantify the disease in future surveys, considering 10% error, each area should have 130rows and 12 plants/row sampled. The disease spatial pattern was studied in 11 planting areas in plots with 480 plants, using mapping, ordinary runs, fitting of β-binomial distribution and spatial autocorrelation analyses. Seven areas showed agregation of diseased plants and four areas presented the randomized pattern suggesting that there is not a single spatial pattern of the diasease in field.Thirty-six pathogen isolates were characterized in relation to epidemiological components, races and isoenzymatic patterns. The disease incidence separated isolates into two similarity groups but based upon the area under the disease progress curve (AUPDC) and progress rate there was three groups. Only one isolate belonged to race 1 while all the others were race 2 suggesting a small population variability regarding to races. The relative mobility of bands indicated six similarity groups for esterases and eight groups for fosfatase. There were no significant correlations among the relative mobility values for isozymes and the values for epidemiological components. In the resistance assay the disease temporal progress was analysed in 25 tomato cultivars inoculated with isolates of races 1 and 2. Race 2 isolates induced disease symptoms in all cultivars but race 1 isolates only induced symptoms in cultivars Santa clara I-5300, Jumbo AG-592, Barão Vermelho AG-591, Débora Plus AF-799, Débora and Viradouro. The cultivars Seculus and Rio Grande showedlonger incubation periods and smaller incidence values, progress rate and AUPDC, suggesting their use in programs of Fusarium wilt integrated management in Agreste of Pernambuco. / A cultura do tomateiro estaqueado apresenta expressiva importância na região Agreste do Estado de Pernambuco tendo, contudo, sua produção é limitada devido à ocorrência de murcha-de-fusário, causada por Fusarium oxysporum f.sp. lycopersici. Este estudo objetivou realizar o levantamento da intensidade da murcha-de-fusário em áreas de plantio no município de Camocim de São Félix, Agreste do Estado de Pernambuco, determinar o tamanho ideal da amostra para quantificação da doença, analisar o arranjo espacial da doença no campo, caracterizar a variabilidade de populações de F. oxysporum f.sp. lycopersici e selecionar cultivares de tomateiro resistentes às raças 1 e 2 do patógeno. No levantamento da intensidade da murcha-de-fusário em 50 áreas de plantio, foi constatada uma alta prevalência da doença (72%), com incidência média de 17,15%. Utilizando os dados de incidência de 36 áreas como amostragens-piloto o tamanho de amostras para quantificação da doença foi determinado com base no coeficiente de variação da média. O número de linhas por área, a ser amostrado, reduziu com a elevação da incidência da doença e do erro aceitável. Considerando o nível de erro de 10%, a amostragem em cada área de 130 linhas com 12 plantas/linha é apropriada para quantificar a incidência da doença em levantamentos futuros. O arranjo espacial da doença foi investigado em 11 áreas de plantio, numa parcela de 480 plantas/área, utilizando-se as análises de mapeamento, “ordinary runs”,ajuste à distribuição beta-binomial e autocorrrelação espacial. Em sete áreas ficou evidenciada a agregação de plantas doentes, enquanto que em quatro, ficou evidente o arranjo aleatório, indicando não haver um padrão único de arranjo espacial da doença no campo. Na caracterização da variabilidade de F. oxysporum f.sp. lycopersici, 36 isolados foram avaliados em relação a componentes epidemiológicos, a raças e a padrões isoenzimáticos. Com base na incidência da doença foi possível a separação dos isolados em dois grupos de similaridade, elevando-se para três quando consideradas a área abaixo da curva de progresso da doença e a taxa de progresso. Apenas um isolado foi caracterizado como pertencente à raça 1, enquanto os demais foram pertencentes à raça 2, indicando uma pequena variabilidade na população quanto à raça. O padrão isoenzimático possibilitou a separação dos isolados em seis grupos de similaridade para esterase e oito grupos para fosfatase. Não foram constatadas correlações significativas entre os valores da mobilidade relativa para as isoenzimas e os obtidos nos componentes epidemiológicos. Na avaliação da resistência ao patógeno, foi analisado o progresso temporal da murcha-de-fusário em 25 cultivares de tomateiro inoculadas com isolados das raças 1 e 2. Todas as cultivares apresentaram plantas com sintomas da doença, quando inoculadas com os isolados da raça 2, enquanto apenas as cultivares Santa Clara I-5300, Jumbo AG-592, Barão Vermelho AG-591, Híbrido Débora Plus AF-799, H. Débora e Viradoro evidenciaram suscetibilidade ao isolado da raça 1. As cultivares H. Seculus e Rio Grande destacaram-se das demais ao propiciarem os maiores períodos de incubação e os menores valores de incidência, de taxa de progresso e de área abaixo da curva de progresso da doença, indicando o potencial para utilização em programas de manejo integrado da murcha-de-fusário no Agreste de Pernambuco.

The cowpea is very important for the poor populations of the North and Northeast of the Brazil. Several factors corroborate to production low of the culture, among them we can quote the disease, focusing on cowpea Fusarium wilt , caused by the fungus Fusarium oxysporum f.sp. tracheiphilum. This study aimed to evaluate the influence of incorporation of crop succession on the severity of cowpea Fusarium wilt. In all experiments we used soil without previous history of cultivation with this culture. There were no observed F. oxysporum populations indigenous in the soil. The experiments were conducted in microplots of concrete pipes containing soil artificially infested with the pathogen structures, the density of 5x103 cfu g-1 of soil. The experiment consisted of three cultivation cycles being: (i) cowpea, (ii) succession cultural and (iii) cowpea. The culture succession were: corn - MI, sorghum - SO, cotton - AL, castor - MN and sunflower - GI; legumes: Crotalaria juncea - CJ, Crotalaria spectabilis - CS, bean-pig - FP, pigeon pea Dwarf - GA, lab-lab - LA and black velvet - velvet MP and dwarf - MA. There were still some treatments: plots with cowpea without inoculum of F. o. f. sp. tracheiphilum - TEST, plots of cowpea inoculated with F. o. f. sp. tracheiphilum (cowpea) - CA, and plots infested with the pathogen in fallow system - PO. The incorporation of succession before of the cowpea planting provided a range in the disease severity of 56.67% to 26.33%. Among the legumes studied the FP and MP were the most suitable for reducing the severity of the disease and offer better grain yield. For succession crops to the OS and GI showed a greater reduction in severity of Fusarium wilt of cowpea. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O feijão-caupi é muito importante para as populações carentes do Norte e Nordestes brasileiro. Diversos fatores corroboram para as baixas produções da cultura, dentre eles podemos destacar as doenças, com foco à murcha-de-fusário do feijão-caupi, causada pelo fungo Fusarium oxysporum f.sp. tracheiphilum. O presente trabalho teve como objetivo avaliar a influência da incorporação de sucessões de cultivo na severidade da murcha-de-fusário do feijão-caupi. Em todos os experimentos utilizouse solo sem histórico anterior de cultivo com a cultura. Não foram detectadas populações autóctones de F. oxysporum no solo. Os experimentos foram conduzidos em microparcelas constituídas de manilhas de concreto contendo solo infestado artificialmente com estruturas do patógeno, na densidade de 5x103 ufc g-1 de solo. O experimento foi constituído de três ciclos de cultivos: (i) feijão-caupi, (ii) sucessões culturais e (iii) feijão-caupi. As sucessões culturais foram compostas por cultivos agrícolas: milho - MI, sorgo - SO, algodão - AL, mamona - MN e girassol - GI; leguminosas: crotalária juncea - CJ, crotalária spectabilis - CS, feijão-de-porco - FP, guandu anão - GA, lab-lab - LA e mucuna-preta - MP e mucuna-anã - MA. Constaram ainda como tratamentos: parcelas com feijão-caupi sem inóculo de F. o. f. sp. tracheiphilum - TEST, parcelas de feijão-caupi inoculadas com F. o. f. sp. tracheiphilum (caupi) CA, e parcelas Infestadas com o fitopatógeno em sistema de pousio - PO. A incorporação das sucessões antecedendo o plantio do feijão-caupi proporcionou uma amplitude na severidade da doença de 56,67% a 26,33%. Dentre as leguminosas estudadas o FP e a MP foram os mais indicados, por reduzirem a severidade da doença e apresentarem melhor produção de grãos. Para os cultivos agrícolas as sucessões com o SO e GI, apresentaram a maior redução da severidade da murcha- de-fusário do caupi.