Ciências Agrárias
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Resultados da Pesquisa
Item Análise proteômica de plantas antagonistas em reposta à inoculação com Meloidogyne javanica(Universidade Federal de Viçosa, 2014-02-25) Amora, Deisy Xavier; Ferraz, Silamar; http://lattes.cnpq.br/6438299352812794Os nematoides do gênero Meloidogyne são fitopatógenos responsáveis por reduções de até 12% na produção e podem ser manejados de forma eficiente com a rotação de culturas, no entanto, por serem polífagos essa técnica é dificultada pela falta de boas opções de plantas não hospedeiras. Assim, faz-se necessário avaliar culturas economicamente viáveis aos produtores para o cultivo em áreas infestadas, como, por exemplo, as plantas antagonistas de uso medicinal e, ou ornamental. Embora algumas substâncias nematicidas já tenham sido isoladas destas plantas, ainda são escassos os estudos direcionados à compreensão dos mecanismos envolvidos na supressão do desenvolvimento dos nematoides nas plantas antagonistas. Assim, objetivou-se neste trabalho avaliar o comportamento de plantas medicinais e ornamentais quando inoculadas com M. javanica e identificar proteínas diferencialmente expressas por essas plantas em resposta à inoculação do nematoide utilizando a eletroforese bidimensional e a espectrometria de massa. As plantas testadas foram: falso-boldo (Plectranthus barbatus), hortelã-pimenta (Mentha piperita), zínia (Zinnia elegans) e losna (Artemisia absinthium). Tomateiro (Solanum lycopersicum) foi utilizado como controle suscetível e crotalária (Crotalaria spectabilis) como planta não hospedeira. Houve baixa reprodução de M. javanica nas raízes de todas as plantas antagonistas testadas. Não foram visualizados nematoides nas raízes de hortelã-pimenta e falso boldo e, em losna, poucas galhas e fêmeas adultas. Nas raízes de zínia e crotalária foram encontrados nematoides pouco desenvolvidos, alguns em formato salsichoide, mas raramente fêmeas totalmente desenvolvidas, mesmo após 30 dias da inoculação. Das plantas antagonistas testadas, as mais eficientes para o controle de M. javanica iiforam hortelã-pimenta, zínia e crotalária. Para identificação das proteínas diferencialmente expressas foram avaliadas amostras de raízes de C. spectabilis e Z. elegans às 24 e 48 horas após a inoculação com o nematoide. As proteínas foram extraídas pelo método fenol-SDS e separadas por eletroforese bidimensional. Por meio da análise comparativa dos géis foram detectadas proteínas diferencialmente expressas e foram posteriormente identificadas por espectrometria de massa. Em C. spectabilis foram identificadas quatro proteínas diferenciais às 24 horas após a inoculação: V-type proton ATPase subunit B 1-like, ATP synthase subunit beta, mitochondrial-like Glyceraldehyde-3-phosphate dehydrogenase e Heat Shock Protein. Estas proteínas estão relacionadas com o restabelecimento da homeostase sob condições de estresse biótico. Em Z. elegans foi identificada a proteína metionina adenosiltransferase, diferencialmente expressa às 48 horas após a inoculação, que pode estar ligada a resposta de defesa da planta através da síntese de etileno, peróxido de hidrogênio e alcaloides pirrolizidínicos Esses resultados contribuem para o entendimento dos mecanismos de defesa das plantas antagonistas à M. javanica.Item Genômica comparativa e potenciais mecanismos de patogenicidade de Pseudomonas que infectam o cafeeiro em Minas Gerais, Brasil(Universidade Federal de Viçosa, 2019-07-22) Alves, Francisco Henrique Nunes da Silva; Pacheco, Jorge Luis Badel; http://lattes.cnpq.br/9683209136098886As manchas bacterianas causadas por Pseudomonas syringae pv. garcae (Psgc), P. syringae pv. tabaci (Psta) e Pseudomonas cichorii (Pch) são umas das principais doenças bacterianas que comprometem a produção de café no Brasil. Para entender a diversidade genética e os mecanismos subjacentes à patogenicidade destas espécies/patovares bacterianas, este estudo primeiro (Capítulo 1) demonstrou as suas organizações genômicas, encontrou regiões de sintenia e diferenças nas sequencias, com marcada ocorrência de transposições, deleções/inserções e inversões. Comparação entre os proteomas das espécies/patovares, revelou 581 proteínas exclusivas de Psgc, 834 exclusivas de Psta, 1486 exclusivas de Pch e 3424 comuns entre os três patógenos bacterianos. Análise do pangenoma e árvores filogenéticas, baseadas no conteúdo gênico do pangenoma e SNP do genoma core, determinou que as espécies/patovares bacterianas possuem plasticidade genômica. Mediante análise filogenética baseada em identidade média de nucleotídeos (ANIb) as espécies/patovares foram separadas em distintos clados. Assim, os resultados deste estudo indicaram que as bactérias patogênicas ao cafeeiro apresentam alta diversidade genética. Na segunda parte (Capítulo 2), uma análise comparativa dos sistemas de secreção e efetores do tipo III desses fitopatógenos foi realizada, usando como referencia o cluster de genes hrp/hrc da bactéria modelo P. syringae pv. tomato DC3000 (Pst DC3000). Encontrou-se que os genes hrpA, hrpD, hrpF, hrG, hrcQa e hrpJ de Psgc não possuíram identidade de sequência quando comparados com os genes do cluster de Pst DC3000, enquanto os demais genes identificados possuíram identidade de sequência que variaram de 26 a 98%. Em Psta os genes hrcJ, hrpG, hrcS, hrpP, hrpQ e hrpJ não obtiveram similaridade com os genes do cluster de Pst DC3000, enquanto os demais genes identificados possuíram identidades de sequência que variam de 41 a 94%. Em Pch, poucos genes mostraram identidade de sequência com os genes do cluster de Pst DC3000, variando de 27 a 58%. Comparações entre os pansecretomas do tipo III das diferentes espécies/patovares mostrou que de 46 famílias de efetores identificados em Psgc, as famílias avrB, avrPto, hopY, hopZ, hopAI, hopAU, hopBI, hopAJ, hopH, hopAF, hopBF e 10 possíveis novos efetores foram exclusivos. Em Psta, das 43 famílias de efetores identificados, somente foram exclusivos hopI, hopM, hopQ, hopAB, hopAZ e 13 novos candidatos à efetores. Em Pch, hopA, hopB, hopBN e 10 possíveis novos efetores foram exclusivos. Foi observado que avrE foi a única família de efetores compartilhada entre as três espécies/patovares bacterianas. Assim, os resultados indicam que o efetor avrE pode possuir papel fundamental nas interações dessas bactérias com o cafeeiro, e a descoberta de novos efetores pode ajudar a entender como cada espécie/patovar se adaptou ao hospedeiro. Por último (Capítulo 3) pretendendo encontrar os mecanismos de adaptação comuns entre as Pseudomonas patogênicas ao cafeeiro, identificou-se as proteínas secretadas pelo sistema de secreção do tipo II (T2SS) e potenciais efetores do tipo II (T2SE). Foi identificada a presença de 368 proteínas não redundantes que possuíram sinal de secreção de tipo II e ausência de domínio transmembranar em Psgc, 420 em Psta e 459 em Pch. Comparando os três pansecretomas do T2SS, foi observado que 240 proteínas estiveram presentes em todas as espécies/patovares analisadas. No entanto, muitas proteínas tiveram anotações relacionadas com funções associadas a membranas, pilus ou flagelo. Filtragem das proteínas associadas com essas estruturas bacterianas revelou T2SE candidatos com atividades enzimáticas potenciais, que ainda não têm sido relatadas como importantes para a patogenicidade bacteriana. Este trabalho proporciona resultados que servem como ponto de partida para pesquisas futuras, visando obter conhecimento sobre a diversidade genética e os mecanismos moleculares que conferem a capacidade de causar doença no cafeeiro aos patógenos Psgc, Psta e Pch. Esses resultados podem também ser úteis para desenvolver novas estratégias que visem controlar os patógenos bacterianos que causam manchas foliares em plantas de café no futuro. Palavras-chave: Pseudomonas Pseudomonas syringae pv. tabaci. cichorii. Pseudomonas syringae pv. garcaeItem Is Fusarium meridionale more adapted as Gibberella Ear and Stalk Rot pathogen of maize than F. graminearum? Comparative epidemiology and toxigenicity(Universidade Federal de Viçosa, 2019-12-20) Machado, Franklin Jackson; Ponte, Emerson Medeiros Del; http://lattes.cnpq.br/0913921835517868Gibberella ear (GER) and stalk rot (GSR) diseases of maize in Brazil are caused mainly by Fusarium meridionale, a species belonging to the Fusarium graminearum species complex (FGSC). Another species within this complex, F. graminearum, is second in importance on maize but is the main species causing Fusarium Head Blight disease of wheat in Brazil. This species is also the predominant cause of GER and GSR in North America, where F. meridionale has never been found. One hypothesis for the observed shift in dominance on different hosts where these species co-occur is that F. meridionale is more fit and adapted on maize than F. graminearum, and vice-versa. We undertook a thorough comparative analysis of pathogenic and saprophytic fitness- related traits using a collection of strains representative of the two species and hosts of origin in order to test this hypothesis. First, four field trials were conducted at different locations and hybrids to compare the aggressiveness (measure of GER severity) of two F. meridionale and two F. graminearum strains, all isolated from maize, inoculated singly or sequentially and alternately at the silking stage. Overall, GER severity was highest in plants inoculated with F. meridionale alone (52.1%); intermediate when inoculation with F. meridionale was followed by F. graminearum (Fmer⇾Fgra, 40.3%) or when F. graminearum was followed by F. meridionale (Fgra⇾Fmer, 38.3%); and lowest in plants inoculated with F. graminearum alone (23.8%). Only nivalenol (NIV) mycotoxin was detected in kernels from F. meridionale inoculations, and deoxynivalenol (DON) was the only mycotoxin found in F. graminearum inoculations. Approximately equal amounts of NIV and DON (1.2:1), along with zearalenone (ZON), were found in Fmer⇾Fgra, but only NIV could be detected in the Fgra⇾Fmer treatments. These results suggested that F. meridionale was more aggressive to maize than F. graminearum. However, this experiment included only a small number of isolates and so in a second study we used a much larger sample comprised of 16 isolates of F. graminearum (12 from wheat, four from maize), and 25 isolates of F. meridionale (nine from wheat, 16 from maize) to inoculate maize ears and stalks in the field. Field trials with four commercial maize hybrids were conducted during the winter and the summer growing seasons in Viçosa, MG. The host of origin made no difference in GER or GSR severity caused by isolates of either species. However, F. meridionale isolates were twice as aggressive as F. graminearum isolates infecting ears, while F. graminearum was, on average, slightly more aggressive on maize stalks than F. meridionale, regardless of the hybrid. Around half of F. graminearum strainsproduced primarily DON and 15ADON, whereas two thirds of F. meridionale strains produced only NIV. Mycotoxins were not detected in the remaining samples. In a third study, a slightly expanded collection consisting of 18 F. graminearum isolates (12 from wheat and six from maize) and 27 F. meridionale isolates (nine from wheat and 18 from maize) were compared in relation to 17 different saprophytic, pathogenic, and toxigenic traits. Although there was significant intraspecies variation for most traits, the strains were strongly structured by species regardless of the host of origin, based on a multivariate analysis. Results showed that F. graminearum was a more aggressive pathogen of wheat and produced higher numbers of macroconidia, perithecia, and ascospores in culture. All F. graminearum strains produced primarily DON in rice cultures or in wheat heads. On the other hand, F. meridionale was a more aggressive colonizer of maize silks and grew faster in culture. All F. meridionale strains produced mainly NIV both in vitro and in planta, with the exception of two strains from maize that produced more DON in wheat heads. The results of this study contribute new data on the biology of these species in subtropical and tropical conditions in Brazil. They suggest that differential aggressiveness and toxigenicity as partial explanations for the predominance of F. meridionale on maize and F. graminearum on wheat, and they lay a foundation for developing further hypotheses to explain these associations. Keywords: Triticum aestivum. Zea mays. Fusarium head blight. Nivalenol. DeoxynivalenolItem Factors affecting the spatio-temporal dynamics of Fusarium wilt of bananas in Brazil(Universidade Federal de Viçosa, 2019-03-29) Heck, Daniel Winter; Mizubuti, Eduardo Seiti Gomide; http://lattes.cnpq.br/4571386054492314Fusarium wilt (FW), caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of bananas. Great yield losses have been recorded for decades. Nevertheless, information about FW epidemiology is scarce. There is no basic information about the disease intensity, spatio-temporal pattern, spread mode and potential factors involved in these processes. This study aims to answer some of the epidemiology gaps to support the design of efficient management strategies. Initially, a survey was carried out in 30 banana fields in the main producing regions of Brazil. In total, 95 ha and more than 100 thousand plants were evaluated. Aggregation of FW was detected by all analytical methods in 43% of the fields. FW was more aggregated in high-input fields. The incidence of FW in banana fields in Brazil is high and is affected predominantly by cultivar, soil physical factors, and field management. The spatio-temporal patterns of FW epidemics were studied in eight plots, totaling 5 ha. All plants were evaluated bimonthly to FW symptoms and spatio-temporal analyses were conducted. The monomolecular model best fit incidence data over time. Aggregated patterns of diseased plants were frequently observed by quadrat-based methods, and the level of aggregation was higher when FW incidence was also high. The clusters of diseased plants were randomly distributed in most plots. The possible aerial dispersal of Foc under field conditions was investigated and spores of the pathogen were caught in Burkard spore trap. To investigate whether weevil borer (Cosmopolites sordidus; WB) was an effective vector of FW a comparative epidemiology study under field conditions and an association study between Foc and WB were performed. Incidence of FW was lower in the field where the population of WB was managed with Beauveria bassiana and higher degree of disease aggregation was observed. A great number of Fusarium spp. isolates were associated with WB but none was Foc. The design of efficient management strategies to mitigate the damage of Foc race 1 and the risk of introduction of Foc tropical race 4 require solid knowledge of FW epidemiology.Item Evolutionary analysis of pathogenicity genes from Erwinia psidii infecting Eucalyptus spp.(Universidade Federal de Viçosa, 2019-07-11) Pereira, Isadora Cristófoli; Pacheco, Jorge Luis Badel; http://lattes.cnpq.br/0401746420777201Erwinia psidii is a Gram-negative bacterium that threatens both guava and eucalypt production. Despite the importance of both trees to the Brazilian economy, little is known about the mechanisms underlying this bacterium pathogenicity. Thus, in this study we used bioinformatic approaches to determine the gene composition of the hrp/hrc cluster of E. psidii, which encodes for the Type III secretion system, a well-known apparatus for its importance to the pathogenicity of many plant pathogenic Gram-negative bacteria. Computational methods were also used to predict both type II and III effector protein repertoires of E. psidii. In addition, evolutionary analyses were performed for the candidate type III effector proteins, in order to gain a better understanding on how this bacterium pathogenicity system evolved over time. Here, we characterized and compared the gene composition of E. psidii hrp/hrc cluster with those of other Enterobacteriaceae, and predicted 11 type III effector proteins, two of which, DspA/E and Eop1, are known important effector proteins secreted by the closely related species E. amylovora. Interestingly, these two candidate type III effectors seem to have been acquired by E. psidii through horizontal gene transfer between Erwinia and Pantoea species. Also, we identified 47 candidate type II effector proteins, most of which were annotated as enzymes, with hydrolytic or non- hydrolytic activities. These results provide important knowledge for further in vivo analysis, through construction of mutant strains and functional characterization of the effector candidates during plant-bacteria interactions.Item Quantitative resistance of Phaseolus vulgaris to common bacterial blight: sources, inheritance and genomic association(Universidade Federal de Viçosa, 2019-02-26) Monteiro, Ana Leticia Rocha; Pacheco, Jorge Luis Badel; http://lattes.cnpq.br/0555377435104333Common Bacterial Blight (CBB), caused by the Gram-negative bacterium Xanthomonas axonopodis pv. phaseoli (Xap) is one of the major diseases that affect common bean production worldwide. To understand diverse aspects of the mechanisms behind resistance of common bean to CBB, this study first (Chapter 1) demonstrated that the use of scissors and multiple needle inoculation methods, that introduce the bacterium directly into the intercellular spaces, result in disease symptoms considered more severe than spray inoculation and, because it resembles natural infection, the latter was chosen to conduct further experiments. Of nine genotypes tested, BRS Radiante and IAPAR 16 exhibited high resistance against seven Xap isolates from different origins. The resistance of these varieties was associated with restriction of bacterial multiplication in planta and was not necessarily related to stomatal density. In the second step (Chapter 2), hybrids of genotype combinations in a partial diallel scheme (3 x 5) were generated to identify the most promising for resistance to CBB, based on estimates of general combining ability (GCA) and specific combining ability (SCA). Because of the lack of reliable morphological markers to distinguish hybrids from parents for several of these combinations, a toolkit of SCAR (Sequence Characterized Amplified Region) markers was assembled. Based on GCA values, it was concluded that variety BRS Radiante greatly contributes to enhance common bean resistance to CBB whereas nine hybrid combinations were shown to be promising to increase resistance to CBB according to SCA values. Then, hypotheses for resistance inheritance in the BRS Radiante × Carioca MG combination were tested by chi-square statistics. The resistance inheritance of BRS Radiante to CBB was best explained by a 9:7 ratio, suggesting that it is conditioned by two complementary dominant genes. In addition, a maximum likelihood analysis indicated the effect of a main dominant gene with additive effect and polygenes involved in CBB resistance. In the third step (Chapter 3) of this work, BC 1 F 1 and BC 2 F 1 plants derived from the combination BRS Radiante (parental donor) × Carioca MG (recurrent parent) were obtained. The backcrossed plants obtained were genotyped with SCAR markers and phenotyped for resistance to CBB. Two BC 1 F 1 and BC 2 F 1 plants were highly resistant to CBB, indicating that they are excellent candidates to advance them to the next generations. Finally (Chapter 4), it was aimed to classify 103 common bean varieties for resistance to CBB based on disease severity and area under the disease progress curve (AUDPC). Twenty-nine varieties with high levels of horizontal resistance to CBB associated with lower AUDPC values were identified. Then, an exploratory Genome- Wide Association Study (GWAS) was conducted with 80 of these varieties using 384 Single Nucleotide Polymorphism (SNP) markers. Genes coding for proteins whose putative functions have previously been associated with plant resistance to diseases, such as serine/threonine kinases, glutamine synthetases, lectin-domain proteins, among others, were identified. The main contributions of this study to the scientific community are: knowledge on common bean genotypes highly resistant to CBB; knowledge on generation of genotype combinations appropriate to obtain resistance against CBB; biological material useful to undertake studies on the genetic and molecular mechanisms underlying common bean resistance against CBB; candidate genes that may be involved in the resistance response of common bean to Xap; and molecular tools useful in the identification of common bean hybrid plants. The knowledge and biological material generated in this work set the stage for additional studies on the common bean-X. axonopodis pv. phaseoli interaction.Item Population structure of Fusarium oxysporum f. sp. cubense in Brazil(Universidade Federal de Viçosa, 2019-07-26) Batista, Izabel Cristina Alves; Mizubuti, Eduardo Seiti Gomide; http://lattes.cnpq.br/0943580960513162Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc), is considered one of the most destructive diseases of bananas. Population genetics studies are required for implementing a molecular epidemiology approach, which in turn is fundamental for effective management or mitigation actions. In this study, a collection of 200 monosporic isolates from several banana producing regions with different climate conditions along a South to North transect in Brazil was formed to assess the genetic structure of the population of Foc. The VCG of 140 isolates was determined by pairing against 17 VCG testers. A group of 158 isolates was selected for microsatellite genotyping. There was moderate diversity of Foc in Brazil. Eight VCGs were identified: 0120, 0122, 0124, 0125, 0128, 01215, 01220, and 01222. The distribution of VCGs is uneven, independent of the banana genotype and varied according to geographic regions. Four SSR loci were polymorphic and on average 7.5 alleles were detected per locus. Thirty-five MGL were identified. There was no association between VCG and SSR and no genetic structure of the population of Foc in Brazil was detected. Keywords: Panama. Wilt. Banana.Item Tomato early blight biocontrol and plant growth promotion by Clonostachys spp.(Universidade Federal de Viçosa, 2019-02-26) Rodrigues Junior, Orlando Maciel; Abreu, Lucas Magalhães deGiven that fungal biocontrol agents not only suppress diseases, but also confer benefits for plants, this work aimed to evaluate the effect of different Clonostachys species against tomato early blight and on plant growth and biomass accumulation. Regarding biocontrol, we hypothesized that non-pathogenic, epiphytic isolates of Cladosporium added to leaf surfaces could act as a living support for the mycoparasitic Clonostachys spp. in a combined application scheme, enhancing the biocontrol effects. We also hypothesized that extending the Clonostachys application after the Alternaria linariae inoculation might provide a ‘curative’ effect on diseased plants. First, isolates of five Clonostachys species were sprayed alone or in combination with a mix of four Cladosporium spp. isolates twice before pathogen inoculation. No marked evidence was found to support the benefit of combined application of these BCA’s. In the second assay, preventive spraying with single isolates of three Clonostachys species resulted in in more than 50% reduction in disease intensity, reaching a maximum of 72% with C. chloroleuca isolate UCBV 12. Additional post-inoculation spray did not result in enhanced biocontrol efficacy or detectable curative effects. In a distinct set of experiments, 21 isolates from nine different Clonostachys species, plus two isolates of Beauveria and Trichoderma, were tested for growth promotion of tomato seedlings after either single-step seed microbiolization or seed microbiolization followed by biodrenching of saturated conidial suspensions after seedling emergence. Tomato seedlings were evaluated for length and dry matter. Single-step seed microbiolization was inefficient in viproviding benefits. Contrastingly, clear plant growth promotion effects were detected after biodrenching. Seven isolates from five Clonostachys species consistently resulted in significant plant mass increases ranging from 21% to 33%, the latter result obtained with the isolate UCBV 35 of C. byssicola. Clonostachys isolates probably were able to colonize rhizosphere due to more efficient form of conidial delivery through drenching, a practice that can be easily adopted in tomato seedling production. Plant growth promotion seems to be another common feature of Clonostachys genus, just as the mycoparasitism ability.Item Fumonisina e zearalenona em grãos de milho no Brasil(Universidade Federal de Viçosa, 2018-07-31) Mendonça, Laís Barbosa Prazeres; Zambolim, Laércio; http://lattes.cnpq.br/0317078489954319O milho é uma das principais commodities do Brasil. Embora a produtividade da cultura tenha aumentado significativamente nos últimos anos, as micotoxinas produzidas por fungos toxigênicos são uma das principais barreiras para a comercialização de grãos e rações. No Brasil, aproximadamente 45% dos grãos de milho estão contaminados com micotoxinas, o que constitui uma grande preocupação para a saúde humana e animal. Neste trabalho, realizado por uma parceria público-privada, realizamos uma pesquisa sobre a ocorrência de fumonisinas e zearalenona em grãos de milho. As amostras foram coletadas em 173 localidades das quatro principais regiões produtoras, em duas safras de primeira safra (verão) e duas de segunda safra (safra de inverno) nos anos de plantio de 2015 a 2017. Todas as amostras de grãos das três safras foram sujeitas à análise fitopatológica e de micotoxinas e estimativas da porcentagem de grãos podres. Informações sobre o sistema de produção agrícola foram obtidas no momento da amostragem através da aplicação de questionários aos agricultores. Na tentativa de identificar a existência de um padrão entre a ocorrência de micotoxinas em grãos e de chuvas durante o período de crescimento, a ocorrência de grãos podres e fatores do sistema de produção, os dados foram submetidos à análise de Redes Neurais Artificiais. Além disso, foram desenvolvidos mapas mostrando a contaminação de fumonisinas e zearalenona nas regiões produtoras de milho no Brasil.Item Estimation of the time-varying apparent infection rate from plant disease progress curves: a particle filter approach(Universidade Federal de Viçosa, 2019-08-12) Alves, Kaique dos Santos; Del Ponte, Emerson Medeiros; http://lattes.cnpq.br/3166163630863998The parameters of the simplest (two-parameter) epidemiological models that best fit plant disease progress curve (DPC) data are biologically meaningful: one is the surrogate for initial inoculum (𝑦 0 ) and the other is the (constant) apparent infection rate (𝑟), both being useful for understanding, predicting and comparing epidemics. The assumption that 𝑟 is constant is not reasonable and fluctuations are expected due to systematic changes in factors affecting infection (e.g. weather, host susceptibility, etc.), thus leading to a time-varying 𝑟, or 𝑟 𝑘 , being 𝑘 = 1,2, . . . , 𝑁 and 𝑁the final epidemic time. A rearrangement in formulation of these models (e.g. logistic, monomolecular, etc.) can be used to obtain 𝑟 between two time points, given the disease (𝑦) data are available. We evaluated one of the several data assimilation techniques, the Particle Filter (PF), as an alternative method for estimating 𝑟 𝑘 . Synthetic DPC data for hypothetical polycyclic epidemics were simulated using the logistic differential equation for scenarios that combined five patterns of 𝑟 𝑘 (constant, increasing, decreasing, random or sinusoidal); five increasing time assessment interval (𝛥𝑡 = 1, 3, 5, 7 or 9 time units - t.u.); and two levels of noise (0.1 or 0.25) assigned to 𝑦 𝑘 . The analyses of 50 simulated 60-t.u. DPCs showed that the errors of PF-derived𝑟̂ 𝑘 were lower (RMSE < 0.05) for 𝛥𝑡 < 5 t.u. and less affected by the presence of noise in the measure compared with the logit-derived 𝑟 𝑘 . The ability to more accurately estimate 𝑟 𝑘 may be useful to increase knowledge of field epidemics and identify within-season drivers of 𝑟 𝑘 behaviour. Keywords: Data assimilation. Inverse problems. Sequential Monte Carlo.