Research investigates the chemical basis for Fusarium head blight (FHB) resistance and initiating development of a screening test for resistant wheat genotypes. The focus is on minimizing cost of screening and gaining chemical approach against FHB. Wheat bran/agar plates (8% bran, w/v) prepared from hard red spring wheat with different susceptibility to FHB were inoculated with F. graminearum. Fusarium plaque diameters and ergosterol levels after 4 days of growth were significantly lower (p< 0.05) on plates prepared from genotypes with low FHB susceptibility than from high FHB susceptible genotypes. F. graminearum growth was lower, when methanol-soluble compounds (MSC) extracted from a low FHB susceptibility genotype, Glenn, were added to high susceptibility genotype, Samson. Wheat bran/agar plates enriched with linoleic acid significantly (p<0.05) reduced the growth rate of F. graminearum in both Glenn and Samson genotypes. Oxygenated fatty acids, including monohydroxy- and dihydroxy- fatty acids were identified in the MSC.

La Fusariosis de la Espiga de Trigo (FET) causada por Fusarium graminearum genera pérdidas en rendimiento y contaminación de granos con micotoxinas. Existe escasa variabilidad genética a la resistencia en el germoplasma de trigo candeal. La línea recombinante cromosómica endocriada LDN(Dic-3A), presenta promisorios niveles de resistencia. Los objetivos de esta Tesis comprenden: i)- identificar genes implicados en la resistencia a FET en LDN(Dic-3A); ii)- transferir el QTL de resistencia de LDN(Dic-3A) a variedades susceptibles de trigo candeal; iii)- desarrollar un ensayo in vitro en plántula para identificar genotipos resistentes y su relación con la severidad de la enfermedad. La identificación de la expresión diferencial de genes inducida en diferentes tiempos postinoculación con F. graminearum entre LDN(Dic-3A) y el parental susceptible LDN se basó principalmente en la técnica de cDNA-AFLP. De ~500 fragmentos derivados de transcripción (TDF) identificados con las distintas combinaciones de cebadores utilizados, 85 mostraron expresión diferencial: el 36% y el 19% fueron identificados en LDN(Dic-3A) y LDN, respectivamente, mientras que el 45% se indujeron en ambos genotipos. Los patrones de TDFs obtenidos mediante cDNA-AFLP demostraron ser reproducibles mediante la técnica de RT-PCR, dando validez a nuestro sistema experimental. La comparación con secuencias depositadas en bases de datos mostró que entre los TDFs identificados se hallan proteínas asociadas a la respuesta temprana a la infección, receptores NBS-LRR y receptores quinasa involucrados en el reconocimiento específico del determinante de avirulencia del patógeno. Fueron identificados además TDFs que, aunque no pudo asignárseles una proteína o función, resultaron específicos de la respuesta a la inoculación. La identidad de TDFs con ESTs de genotecas de espiga de materiales de T. aestivum inoculadas con F. graminearum constituye un sustento adicional para esta afirmación. El mapeo in silico permitió localizar 28 TDFs en el genoma de T. aestivum, siendo el brazo cromosómico 5BL el más representado, además de obtener las regiones genómicas y regulatorias de varios genes. A partir de estas regiones, pudo determinarse la existencia de mecanismos de regulación de la transcripción en común entre algunos genes asociados a los TDFs, entre ellas las proteínas WRKY implicadas en la regulación de los genes asociados con la defensa ante patógenos. La integración de la información obtenida sugiere que la interacción trigo - F. graminearum no sería una interacción compatible como generalmente se cree sino que se trataría de una interacción “gen a gen” que finalmente lleva a la expresión de genes asociados a la defensa. Hemos asumido además el desafío de desarrollar cultivares de trigo candeal resistentes. La compleja herencia de la resistencia y los efectos ambientales, son los responsables del escaso éxito obtenido hasta el momento por los mejoradores en la incorporación al mercado de cultivares resistentes. En este trabajo, por medio de cruzamientos se incorporó el QTL de resistencia Qfhs.ndsu-3AS de LDN(Dic-3A) en los cultivares BESM y BCAN. El microsatélite Xgwm2, ligado al QTL de resistencia permitió reducir la cantidad de individuos que continuaron en el programa de mejoramiento. En la generación F3, se seleccionaron los individuos homocigotos para el alelo de resistencia, y en F4, se evaluó la severidad en espiga identificando individuos con niveles de resistencia similares o mejores que el parental resistente. El programa de mejoramiento continuará con autofecundaciones de genotipos resistentes hasta alcanzar estabilidad en la resistencia junto con la presencia de caracteres agronómicos de interés. La evaluación del comportamiento ante F. graminearum de nuevos materiales requiere de la existencia de ensayos rápidos y confiables. Hemos desarrollado un ensayo in vitro a través de la evaluación de las variables Germinación, Largo de coleoptilo, Peso de coleoptilo, Peso de raíces, utilizando siete variedades comerciales de trigo candeal, el trigo candeal LDN y las líneas resistentes LDN(Dic-3A) y LDN-DGE1 y dos genotipos de trigo pan A601 y A601S3. Las variables de plántula explicaron entre el 51 y el 74% de la severidad de la enfermedad, siendo Largo y Peso de coleoptilo las más eficaces para predecir la resistencia a FET. Los genotipos introgresados mostraron un buen comportamiento en el ensayo en plántula y menor daño en espiga comparados con los susceptibles, sugiriendo que la prueba in vitro es efectiva para la determinación de la resistencia a FET en diferentes fondos genéticos. Entonces, se propone un ensayo in vitro basado en las variables de coleoptilo para evaluar de manera eficaz, rápida y económica el nivel de resistencia a FET, definiendo el Índice de Resistencia en Plántula, altamente correlacionado con severidad, para cada genotipo. Los principales hallazgos de esta Tesis pueden compendiarse indicando que se ha establecido que la interacción trigo - F. graminearum sería una interacción “gen a gen” que lleva a la expresión de genes asociados a la defensa, la obtención de genotipos de trigo candeal resistente a fusariosis de la espiga y el dearrollo de un ensayo in vitro predictor del comportamiento de los genotipos ante la infección. / Fusarium head blight (FHB) caused by Fusarium graminearum produce yield losses and contamination of grain with mycotoxins. Scarce genetic variability for resistance exists in durum wheat germplasm. The LDN(Dic-3A) recombinant inbred chromosome line showed to be resistant to FBH. The goals of this Thesis include: i)- identification of genes involved in FHB resistance in LDN(Dic-3A); ii)- transference from LDN(Dic-3A) to susceptible durum varieties of the resistance QTL; iii)- development of an in vitro seedling assay to identify wheat resistant genotypes and their relationship with disease severity. Analysis of differential gene expression induced at different time points post- inoculation with F. graminearum between LDN(Dic-3A) and the susceptible parental LDN was performed by cDNA-AFLP technique. A total 85 out of the ~500 transcript-derived fragments (TDFs) identified with the diverse primer combination used showed to be differentially expressed: 36% and 19% were identified in LDN(Dic-3A) and LDN, respectively, whereas 45% were induced in both genotypes. The TDF patterns obtained though cDNA-AFLP showed to be reproducible by RT-PCR, supporting the reliability of our experimental system to identify differentially expressed transcripts. Comparison with protein databases revealed that among the cloned TDFs, several showed identity to proteins associated with early response to infection, to NBS-LRR and kinases receptors involved in specific recognition of avirulence pathogen determinant. However, there was a group of TDFs that, in spite of being specific of the inoculation response, could not be assigned to characterized proteins. The identity of these TDFs with ESTs from libraries from T. aestivum inoculated with Fusarium graminearum additionally supports this affirmation. The availability of T. aestivum genome sequences allowed the in silico mapping of 28 TDFs and the identification of several genes and regulatory regions, being the 5BL chromosome arm where most TDFs were located. The analysis of the regulatory regions revealed the existence of transcription regulation mechanisms shared by some TDFs associated genes, such as WRKY proteins, implied in the regulation of genes associated to pathogen defence. The present results suggest that wheat – F. graminearum interaction is governed by gene-for-gene relationships. The development of resistant cultivars has been a difficult task due to the complex inheritance of resistance and the influence of environmental factors. The resistance QTL Qfhs.ndsu-3AS from LDN(Dic-3A) was incorporated in the cultivars Buck Emeralda and Buck Candisur through crosses. F3 homozygous individuals for the resistance allele were subjected to marker assisted selection using the Xgwm2 microsatellite, linked to the mentioned QTL, allowing a reduction in the number of individuals included in the following steps of the breeding program. In F4, there were selected the individuals that showed equal or better resistance performances compared to the resistant parent, evaluated through the spike severity at 21 days post-inoculation. The breeding program will continue by selfing resistant genotypes to obtain plant materials that possess both stable resistance and suitable agronomic traits. Rapid and trustable assays are required for the evaluation of germoplasm response to F. graminearum infection. In this Thesis, it was developed an in vitro assay through the evaluation of the variables Germination, Coleoptile length, Coleoptile weight and Root weight using seven varieties of commercial durum, durum wheat cv. LDN and the derived resistant lines LDN(Dic- 3A) and LDN-DGE1 and two common wheat genotypes, A601 and A601S3. The seedling variables explained between 51 and 74% of the disease severity, being Coleoptile length and weight the ones that more effectively predicted the resistance to FHB. The introgressed genotypes showed better performance in the seedling assay and relatively lower damage in the spikes in relation to susceptible ones, suggesting that this in vitro test can detect FHB resistance in different genetic backgrouds. Thus, we propose an in vitro assay based on coleoptile variables to perform quick, qualified and cost-effective evaluation of the FHB resistance level, defining the Seedling Resistance Index, highly related to severity, for each genotype. Thus, the present Thesis allowed us to postulate that the interaction wheat – F. graminearum could be classified as “gen-for-gen” leading to the expression of defense-related genes. Concurrently, there were obtained genotypes resistant to F. graminearum and it was developed an in vitro assay that predicts the genotypes reponse to infection.

No description available.

Dry Pea or field pea (Pisum sativum L.) is an important cool season legume crop grown in the United States. Field peas are vulnerable to many diseases of which, soil borne diseases including wilt and root rot are of major economic importance and can cause significant reduction in yield. There is a dearth of satisfactory methods for control of root rot and no varieties with complete resistance to Fusarium root rot are currently available. Root rot disease was found to be prevalent in all the major pea growing counties of North Dakota surveyed in 2004, 2005, 2010 and 2011. Fusarium species were the most frequently isolated fungal species from the infected pea roots of which, F. oxysporum and F. avenaceum were the most common. 21 Field pea varieties were screened for resistance against F. avenaceum and F. solani f. sp. pisi, the Fusarium species traditionally associated with root rots of field pea in growth chamber experiments and field trials. Low levels of resistance were detected in a few cultivars but no variety was found to be completely resistant to any of the pathogens tested. Efficiency of precipitated calcium carbonate (PCC) in controlling Fusarium species most commonly associated with root rots was evaluated under in vitro and field conditions. Significant reduction in spore production, spore germination, and dry mycelial weight of Fusarium spp. were detected on PCC amended media in laboratory studies. In greenhouse and field experiments significant reduction in root rot disease severity was observed with PCC application compared to control. Fungal gene expression in artificially infected field pea roots and F. graminearum grown in culture was assessed using the Illumina mRNA-Seq technology. A total of 613 F. graminearum genes were found to be differentially expressed in planta on pea. Functional classes associated with amino acid metabolism, nitrogen metabolism, extracellular polysaccharide degradation, detoxification by degradation and defense related proteins were found to be significantly enriched in the up-regulated gene set as determined using FunCatDB. Expression of four up-regulated genes was confirmed by RT-PCR to validate the inferences from the sequencing results.

Orientadores: Maria Luiza Moretti, Angélica Zaninelli Schreiber / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-27T08:47:24Z (GMT). No. of bitstreams: 1 Moraes_JoseRenatode_M.pdf: 2487255 bytes, checksum: 4c5a21c13a0b57cf864dbf79cca990fd (MD5) Previous issue date: 2014 / Resumo: Introdução: os fungos do gênero Fusarium são ubíquos no meio ambiente e causam doenças em plantas e aos seres humanos. Objetivos: 1)estabelecer o protocolo para a coleta e o isolamento de Fusarium spp. no ar; 2)isolar fungos do gênero Fusarium do ar da enfermaria de Hematologia e da Unidade de Transplante de Medula Óssea (TMO) no Hospital de Clínicas (HC) da Universidade Estadual de Campinas (UNICAMP) e comparar a relação genética de isolados ambientais de Fusarium spp. com os isolados a partir de hemoculturas de rotina diagnóstica de pacientes hospitalizados durante os anos de 2002 a 2013, 3)identificar os fungos do gênero Fusarium ao nível de complexo de espécies por PCR em tempo real, e ao nível de espécie pelo sequenciamento de fragmento do gene EF1?. Metodologia: foram colhidas amostras de ar nas unidades de TMO (que possui controle de ar através de filtros HEPA e fluxo de ar de pressão positiva) e na Hematologia (unidade sem controle do ar) do HC. De 2006 a 2013 foram identificados 18 isolados de Fusarium spp. em culturas de sangue. A coleta de ar foi realizada através do amostrador de ar BioSamp modelo MBS 1000D (YotsubishiCorp Japão). Um meio de cultura seletivo para Fusarium (Agar Komada com modificações) foi usado na placa de Petri dentro do amostrador de ar. O volume de ar de 1000 mL e 500 mL foram aspirados da Hematologia e enfermarias de TMO, respectivamente. Após o tempo de incubação, as colônias que cresceram nas placas foram avaliadas macroscopicamente e microscopicamente para identificação morfológica. Fusarium spp. foram identificados através de um novo ensaio de PCR em tempo real composto por dois ensaios de PCR em tempo real: um específico para o gênero Fusarium e um ensaio específico para detecção específica do complexo de espécies de Fusarium solani (FSSC). Para confirmar o complexo de espécies de Fusarium, uma região parcial do gene EF-1? foi sequenciado. O alinhamento das sequências foi realizado no programa Clustal W e a análise filogenética utilizou o programa Mega5 com o algorítimo Neighbor-Joininge Bootstrap de 1000 replicatas. Resultado: foram isoladas 108 cepas de Fusarium spp. destes 28% na unidade de TMO e 78% na Hematologia. Os complexos de espécies encontrados foram: 10% FCSC, 21% FIESC, 1% FOSC, 12% FSSC, 51% GFSC e 5% não definido. Na TMO a maior prevalência foi da espécie Fusarium solani (9/30 isolados) e na Hematologia Fusarium verticillioides (25/31 isolados). Não foi possível constatar relevância entre a temperatura e umidade do ar em relação ao aumento ou diminuição de isolados nas coletas. Nove isolados FSSC do ar e 8 de sangue apresentaram BT 99%. Conclusão. Os dados de análise filogenética sugeriram que os isolados de sangue de pacientes e ambientais foram similares sugerindo que o ambiente pôde representar uma fonte potencial de infecção para os pacientes imunodeprimidos / Abstract: Introduction:the fungus Fusarium are ubiquitous in the environment and cause diseases in plants and humans. Objectives: isolate fungi Fusarium in the air of the ward Hematology and Unit of Bone Marrow Transplantation (BMT) at the Hospital de Clinicas (HC), State University of Campinas (UNICAMP), compare the phylogenetic relationship of environmental isolates of Fusarium spp .with isolates from blood cultures of routine diagnosis of hospitalized patients during the years 2002-2013, to establish protocol for the collection and isolation of Fusarium spp. in the air, identify the fungi Fusarium species complex level by real time PCR, and to species level by sequencing the fragment EF1 ? gene. Methodology: air sample was collected in BMT units (which has control of air through HEPA filters and air flow positive pressure) and Hematology (there is not self control air inlet) HC. From 2006 to 2013, 18 samples obtained from blood cultures with the presence of Fusarium spp. were added to study the relationship between degree of molecular clinical isolates isolated from the air. The air sampling was performed using the Bio air sampler Samp MBS model 1000D (Yotsubishi Corp. Japan). A selective medium for Fusarium (Komada Agar changes by Y. Mikami, Chiba University) was used in the petri dish in the air sampler. The air volume of 1000 mL and 500 mL were aspirated Hematology and BMT wards, respectively. After the incubation time, colonies that grew on the plates were evaluated macroscopically and microscopically for morphological identification. Fusarium spp. were identified by PCR of a new system in real time according to Muraosa et al. comprising two PCR assays in real time: the specific assay Fusarium and a specific assay for specific detection of Fusarium solani (FSSC) complex. To confirm the complex of Fusarium species, a partial region of the EF-1? gene was sequenced. The alignment of sequences was performed in Clustal W program and phylogenetic analysis used Mega5 program with the neighbor-joining algorithm and bootstrap 1000 replicates. Results: 108 ceepas Fusarium spp were isolated. 28% of these isolates form the BMT unit and 78% in Hematology. Overall the species complexes ficarm divided as follows: 10% FCSC, 21% FIESC 1% FOSC, FSSC 12%, 51% and 5% GFSC nd not defined). In the BMT was higher prevalence of the species Fusariu solani (9/30 isolates) and the Hematology espéciecom largest presence is Fusarium verticillioides (25/31 isolates). Unable to find relevance between temperature and air humidity in relation to the increase or decrease in collections of isolates. Nine isolates of Fusarium solani air obtained from the same source ancestras 8 Fusarium solani isolates from blood (BT 99%). Conclusion:Fusarium spp were isolated in 108 environmental samples en all evaluated environments. Phylogenetically findings suggest equivalence between environmental isolates and isolates from the blood of patients. The collection protocol set showed satisfactory for the specific isolation of Fusarium result. The findings of Fusarium were grouped into complexes FSSC and FSSC not the technique of real-time PCR and sequencing of the gene EF1? allowed to classify the isolates in the species level / Mestrado / Clinica Medica / Mestre em Ciências

Deoxynivalenol (DON), a mycotoxin produced in cereal grains infected by Fusarium Head Blight produced by Fusarium graminearium and Deoxynivalenol-3-β-D-glucopyranoside (DON-3G), were studied during processing using LC-MS-MS and GC. DON reduced significantly (P<0.05) 61.8% during milling into flour. Therefore, DON was concentrated mostly in the bran and germ. DON increased 40.8% during the fermentation stage of baking. DON increased in dough more than flour and mixed dough. Milling reduced by 23.7% but fermentation did not. But bread was significantly lower in DON-3G at 0.15 ppm than flour and dough at 0.31 ppm. The baking increased DON and decreased DON-3G showing a difference in stability of the mycotoxins during processing. Enzyme hydrolysis on DON using α-amylase, cellulase, protease, and xylanase, showed a significant increase with cellulase (20.8%), protease (11.4%), and xylanase (35.6%) compared to wheat composite. DON may be bound to the cell wall or protein component of the kernel.

Thesis (Ph.D. (Chemistry)) -- University of Limpopo, 2021 / Fusarium species are among pathogenic organisms responsible for massive yield and quality losses in crop production. They cause crop diseases in the field and during storage, and some species are capable of producing mycotoxins which contaminate products and threaten consumer s’ health. Conventional synthetic fungicides are available for the control of Fusarium pathogens, however, their applications have been restricted or discouraged due to their harmful effect on the environment, livestocks and human health. There are also reports about fungal-resistance to available fungicides. Moreover, the synthetic chemicals are not affordable to smallholder farmers and to some extent, they are not recommended for applications in organic farming. As an alternative to these fungicides, selected medicinal plant species were investigated as sources of natural chemicals or compounds with potential to be developed into plant-based fungicides to control Fusarium pathogens. This study aimed to identify antifungal extracts among the selected medicinal plant species which could be used to develop plant-based fungicides to control Fusarium diseases. It also focused on isolation and characterization of antifungal compounds from selected medicinal plant species. Thirteen medicinal plant species (Combretum erythrophyllum (Burch.) Sond , Melia azedarach L, Solanum mauritianum Scop, Nicotiana glauca Graham, Schotia brachypetala Sond, Lantana camara L, Combretum molle R. Br. ex G. Don, Quercus acutissima Carruth, Olea europaea L, Vangueria infausta Burch, Withania somnifera (L.) Dunal, Harpephyllum caffrum Bernh and Senna didymobotrya (Fresen.) H.S. Irwin & Barneby) were selected from literature based on their reported strong antimicrobial activity against human and/or animal pathogens. The leaves of these plant species were collected, shade-dried and extracted with water, petroleum ether, ethyl acetate and acetone. Extractant yield was recorded and each extract was evaluated for antifungal activity using a micro-dilution assay against nine Fusarium pathogens (Fusarium verticillioides, Fusarium proliferatum, Fusarium subglutinans, Fusarium graminearum, Fusarium solani, xxvii Fusarium oxysporum, Fusarium semitectum, Fusarium chlamydosporum and Fusarium equiseti). Similar solvent extracts from different plant species that demonstrated MIC value of less than 0.1 mg/ml against the same pathogen were combined and evaluated for antifungal activity. The interation effect of combined extracts was determined by calculating their fractional inhibitory concentration index (FICI) in order to determine their possible synergistic, additive, indifference or antagonistic antifungal activity against tested pathogens. Plant extracts demonstrating synergistic and or additive interaction were further evaluated in combination and individually for in vivo antifungal activity against maize seed Fusarium pathogens. At least, one of the extracts obtained from these medicinal plant species showed strong antifungal activity with minimum inhibitory concentration (MIC) of less than 0.1 mg/ml against at least one of the tested pathogens. Of the four solvent extracts evaluated, acetone and ethyl acetate extracts showed stronger antifungal activity compared to petroleum ether and water extracts. Of the nine pathogens tested, F. proliferatum was the most susceptible and was strongly inhibited (MIC < 0.1 mg/ml) by 41 plant extracts whilst F. equisite was found to be resistant with MIC < 0.1 mg/ml by only three plant extracts. In total, each pathogen was tested against 52 plant extracts. There were 17, 16 and 15 extracts from C. erythrophyllum, S. mauritianum and Q. acutissima, respectively, with MIC values less than 0.1 mg/ml. These species were the most active when tested individually. Schotia brachypetala was found to be the least active medicinal plant with only seven extracts demonstrating very strong activity (MIC < 0.1 mg/ml) against the tested pathogens. Minimum inhibitory dilution (MID) or total activity was also calculated and it was found that water and acetone extracts had the highest MID, followed by ethyl acetate extracts while petroleum ether extracts recorded the lowest. Of all plant extracts tested against the nine pathogens, 59 plant extracts demonstrated MID values of more than 1000 ml/g. Out of the 348 extract combinations evaluated, 116 and 87 extract combinations demonstrated synergistic and additive antifungal activity, respectively. The strongest activity xxviii recorded for the combined extracts resulted from synergistic interaction with MIC value of 0.001 mg/ml against F. proliferatum and F. verticilloides. Combined acetone extract of C. erythrophyllum and Q. acutissima was very active (95.75% inhibition) against F. verticilloides inoculated on maize seeds while individual preparation from M. azedarach acetone extract demonstrated 97.10% inhibition against F. proliferatum. The extracts showing good antifungal activity (≥ 50% inhibition) were further tested for phytotoxicity on maize seed germination and the lowest recorded seed germination was 86.25%, resulting from Q. acutissima ethyl acetate extract. Combined acetone extract of C. erythrophyllum and Q. acutissima did not significantly affect maize seedling growth when compared to negative control (water treatment). All plant extracts that showed strong activity (MIC < 0.1 mg/ml) when tested using micro-dilution assay were spotted on thin layer chromatography (TLC) bioautographic assay to establish and determine the number of active compounds or bands. The white spots observed on the chromatograms indicated the presence of antifungal compounds. Combretum erythrophyllum, W. somnifera and L. camara exhibited the presence of antifungal compounds against 7, 5 and 4 pathogens, respectively. Hence, these plant species were selected for isolation of antifungal compounds where open column chromatography and preparative TLC were used for compound purification. At least, three isolated fractions from the three plant species were found to be active (MIC values ranging from 0.0098 to 0.625 mg/ml) against more than five pathogens. The fractions were also found to contain different levels of phytochemicals such as glycosides, flavonoids, steroids, and terpernoids. The structures of isolated compounds or fractions were determined using nuclear magnetic resonance (NMR) and mass spectroscopic (MS) techniques. A mixture of apeginin (4′,5,7-trihydroxyflavone) and salvigenin (5-hydroxy-6,7,4'-trimethoxyflavone) isolated from the leaves of C. erythrophyllum showed strong antifungal activity (MIC values ranging from 0.01 mg/ml to 0.63 mg.ml) against 5 tested Fusarium pathogens. Also isolated from C. erythrophyllum was a derivative of maslinic acid and it has xxix shown antifungal activity with MIC values ranging from 0.08 mg/ml to 0.63 mg/ml against 6 tested pathogens. On the other hand, lantadene A (22- angeloyloxy-9-hydroxy-3-oxo-olean-12-en-28-oic acid), boswellic acid (11-keto-β-boswellic acid) and boswellic acid glycoside isolated from the leaves of Lantana camara showed good activity (MIC values ≤ 0.63 mg/ml) against one or more Fusarium pathogens. Withaferin A (4β,27-dihydroxy-1-oxo-5β,6β-epoxywitha-2-24-dienolide) glycoside isolated from the leaves of Withania somnifera showed antifungal activity with MIC value of 0.16 mg/ml against F. verticilloides. This study demonstrated potential applications of medicinal plant extracts as cheap, accessible and sustainable source of eco-friendly pesticides for fighting crop diseases in organic and smallholder farming. The extracts can be used as treatment agents to control maize seed spoilage during post-harvest storage. Additionally, characterised antifungals may serve as scaffold compounds during commercial synthesis of plant-based fungicides. / Agricultural Research Council (ARC) and National Research Foundation (NRF)

Made available in DSpace on 2016-12-08T16:44:38Z (GMT). No. of bitstreams: 1 PGPV08MA070.pdf: 802379 bytes, checksum: 9372189c25f1c83cdbd51679c5fdeec8 (MD5) Previous issue date: 2008-03-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The infected seeds are an important primary inoculum source for fungus that cause seed deterioration and root rot, stalk rot and ear in corn. This study was performed in laboratory and aimed to assess the sanity of maize seeds treated with fungicides commercialized in Santa Catarina and Rio Grande do Sul states determining the incidence and frequency of fungus associated with seed occurrence; identify fungicides in seeds treatment with eradicating action against Fusarium verticillioides ; adjust fungicides doses to the eradicative control of F. verticillioides ; assess the seed treatments with fungicides eradicatives of F. verticillioides related with germination and emergence of seedlings and quantify the F. verticillioides transmission rate from seeds to the mesocotyl, crown and coleoptile of seedlings from seeds with and without the treatment, sowed in soil under five different temperatures. From 224 samples of commercial seeds the highest frequencies of occurrence and incidence were obtained for F. verticillioides, Penicillium spp. and Aspergillus flavus fungi with occurrence medium values of respectively 86,6%, 69,6%, 63,8% and incidence of 14,0%, 12,4% and 8,4%. The results showed that the most used fungicide by seed companies for seed treatment was the mixture fludioxonil + metalaxil. It is concluded that the seed treatment is not eradicating the main fungi of seed. Test with fungicides, blends and doses, in a sample of maize seeds with 41% of F. verticillioides incidence showed better control with carbendazim+tolyfluanid, carbendazim and carbendazim+thiram. The rate adjust was done in these fungicides with AS 1535 hybrid with 37% of F. verticillioides incidence, testing rate indicated by manufacturer, 25%, 50%,75% and 100% beyond than indicated. The carbendazim active principle isolated did not eradicate the fungos. The fungicides carbendazim+ thiram (rate 75% beyond than indicated) and carbendazim+ tolylfluanid (rate beyond than indicated) eradicated the in vitro F. verticillioides fungus. In climatized grout chambers was determined that the F. verticillioides transmission was efficient in the temperature of 21 and 27°C to the mesocotyl and crown in treatment without fungicide. In the temperatures higher than 21°C the control of transmission was not achieved by seed treatment, supporting that the fungicide efficacy in eradicate F. verticillioides must be evaluated in vivo . The highest intensity of root rot was verified in the check control in 21°C with 34.7%, whereas in this temperature were not detected root rottenness symptoms in seeds treated with tolylfluanid+carbendazim. The minor seedlings emergence was obtained at 15°C. At 15ªC and 18°C these fungicides proportionate increase in the emerged plant population. From 21°C on the seed treatment did not influence in the plant population. The fungicides tolylfluanid+carbendazim and carbendazim+thiram showed the best results of F. verticillioides control of transmission. It is possible conclude that the seed is source of primary inoculum to F. verticillioides, the transmission rate is influenced by soil temperature and the seedling emergence in cold soil sowing conditions can be improved with treatment of seeds / As sementes infectadas constituem importante fonte de inóculo primário para os fungos causadores de deterioração de sementes, podridões radiculares, podridões da base do colmo e da espiga em milho. Os trabalhos foram conduzidos em laboratório e tiveram como objetivos avaliar a sanidade de sementes de milho comercializadas no estado de Santa Catarina e Rio Grande do Sul, determinando a incidência e a freqüência de ocorrência de fungos associados às sementes; identificar fungicidas em tratamento de sementes com ação erradicante contra Fusarium verticillioides; ajustar doses de fungicidas para controle erradicativo de F. verticillioides; avaliar tratamentos de sementes com fungicidas erradicativos de F. verticillioides em relação à germinação e emergência de plântulas e quantificar a taxa de transmissão de F. verticillioides da semente para mesocótilo, coroa e coleóptilo de plântulas em sementes com e sem tratamento, semeadas em solo sob cinco temperaturas. De 224 amostras de sementes comerciais avaliadas, as maiores freqüências de ocorrência e incidências foram obtidas para os fungos F. verticillioides, Penicillium spp. e Aspergillus flavus com valores médios de ocorrência de 86,6%, 69,6%, 63,8% e incidência de 14,0%, 12,4% e 8,4%, respectivamente. Os resultados demonstraram que o fungicida mais utilizado pelas companhias de sementes para tratamento foi o principio ativo fludioxonil+metalaxil. Concluiu-se que o tratamento de sementes não está erradicando os principais fungos da semente. Teste com fungicidas, misturas e doses, em amostra de sementes de milho com 41,0% de incidência de F. verticillioides, indicaram melhor controle com carbendazim+tolilfluanida (99,0%), carbendazim (95,5%) e carbendazim+tiram (78,0%). O ajuste de dose foi feito nesses fungicidas com o híbrido AS 1535 com 37% de incidência de F. verticillioides, testando dose indicada pelo fabricante, 25%, 50%, 75% e 100% superior à indicada. O principio ativo carbendazim isolado não erradicou o fungo. Os fungicidas carbendazim+tiram (dose 75% superior à indicada) e carbendazim+tolilfluanida (doses superiores à indicada) erradicaram o fungo F. verticillioides in vitro . Em câmaras climatizadas a transmissão de F. verticillioides foi eficiente na temperatura de 21 e 27 ºC para o mesocótilo e coroa em sementes não tratadas. Nas temperaturas superiores a 21 ºC, o controle da transmissão não foi alcançado pelo tratamento de semente, demonstrando que a eficácia do fungicida em erradicar F. verticillioides deve ser avaliada in vivo . A maior intensidade de podridão radicular foi verificada na testemunha aos 21 ºC com 34,7%, sendo que nesta temperatura não foram detectados sintomas de podridão de raízes em sementes tratadas com tolilfluanida+carbendazim. A menor emergência de plântulas foi obtida na testemunha a 15ºC. A 15ºC e 18 ºC, esses fungicidas proporcionaram incremento na população de plantas emersas. A partir de 21ºC o tratamento de sementes não influenciou na população de plantas. Os fungicidas tolilfluanida+carbendazim e carbendazim+tiram apresentaram os melhores resultados no controle da transmissão de F. verticillioides. Pode-se concluir que a semente é fonte de inóculo primário para F. verticillioides e que a taxa de transmissão é influenciada pela temperatura do solo e que a emergência de plântulas em condições de semeadura de solo frio pode ser melhorada com o tratamento de sementes