Thesis (PhD. (Geography)) --University of Limpopo, 2019 / Of late climate change and consequently, the spread of crop diseases has been identified as one of the major threat to crop production and food security in subSaharan Africa. This research, therefore, aims to evaluate the role of in situ hyperspectral and new generation multispectral data in detecting maize crop viral and fungal diseases, that is maize streak virus and grey leaf spot respectively. To accomplish this objective; a comparison of two variable selection techniques (Random Forest’s Forward Variable, (FVS) and Guided Regularized Random Forest: (GRRF) was done in selecting the optimal variables that can be used in detecting maize streak virus disease using in-situ resampled hyperspectral data. The findings indicated that the GRRF model produced high classification accuracy (91.67%) whereas the FVS had a slightly lower accuracy (87.60%) based on Hymap when compared to the AISA. The results have shown that the GRRF algorithm has the potential to select compact feature sub sets, and the accuracy performance is better than that of RF’s variable selection method. Secondly, the utility of remote sensing techniques in detecting the geminivirus infected maize was evaluated in this study based on experiments in Ofcolaco, Tzaneen in South Africa. Specifically, the potential of hyperspectral data in detecting different levels of maize infected by maize streak virus (MSV) was tested based on Guided Regularized Random Forest (GRRF). The findings illustrate the strength of hyperspectral data in detecting different levels of MSV infections. Specifically, the GRRF model was able to identify the optimal bands for detecting different levels of maize streak disease in maize. These bands were allocated at 552 nm, 603 nm, 683 nm, 881 nm, and 2338 nm. This study underscores the potential of using remotely sensed data in the accurate detection of maize crop diseases such as MSV and its severity which is critical in crop monitoring to foster food security, especially in the resource-limited subSaharan Africa. The study then investigated the possibility to upscale the previous findings to space borne sensor. RapidEye data and derived vegetation indices were tested in detecting and mapping the maize streak virus. The results revealed that the use of RapidEye spectral bands in detection and mapping of maize streak virus disease yielded good classification results with an overall accuracy of 82.75%. The inclusion of RapidEye derived vegetation indices improved the classification accuracies by 3.4%. Due to the cost involved in acquiring commercial images, like xviii RapidEye, a freely available Landsat-8 data can offer a new data source that is useful for maize diseases estimation, in environments which have limited resources. This study investigated the use of Landsat 8 and vegetation indices in estimating and predicting maize infected with maize streak virus. Landsat 8 data produced an overall accuracy of 50.32%. The inclusion of vegetation indices computed from Landsat 8 sensor improved the classification accuracies by 1.29%. Overally, the findings of this study provide the necessary insight and motivation to the remote sensing community, particularly in resource-constrained regions, to shift towards embracing various indices obtained from the readily-available and affordable multispectral Landsat-8 OLI sensor. The results of the study show that the mediumresolution multispectral Landsat 8-OLI data set can be used to detect and map maize streak virus disease. This study demonstrates the invaluable potential and strength of applying the readily-available medium-resolution, Landsat-8 OLI data set, with a large swath width (185 km) in precisely detecting and mapping maize streak virus disease. The study then examined the influence of climatic, environmental and remotely sensed variables on the spread of MSV disease on the Ofcolaco maize farms in Tzaneen, South Africa. Environmental and climatic variables were integrated together with Landsat 8 derived vegetation indices to predict the probability of MSV occurrence within the Ofcolaco maize farms in Limpopo, South Africa. Correlation analysis was used to relate vegetation indices, environmental and climatic variables to incidences of maize streak virus disease. The variables used to predict the distribution of MSV were elevation, rainfall, slope, temperature, and vegetation indices. It was found that MSV disease infestation is more likely to occur on low-lying altitudes and areas with high Normalised Difference Vegetation Index (NDVI) located at an altitude ranging of 350 and 450 m.a.s.l. The suitable areas are characterized by temperatures ranging from 24°C to 25°C. The results indicate the potential of integrating Landsat 8 derived vegetation indices, environmental and climatic variables to improve the prediction of areas that are likely to be affected by MSV disease outbreaks in maize fields in semi-arid environments. After realizing the potential of remote sensing in detecting and predicting the occurrence of maize streak virus disease, the study further examined its potential in mapping the most complex disease; Grey Leaf Spot (GLS) in maize fields using WorldView-2, Quickbird, RapidEye, and Sentinel-2 resampled from hyperspectral data. To accomplish this objective, field spectra were acquired from healthy, moderate and xix severely infected maize leaves during the 2013 and 2014 growing seasons. The spectra were then resampled to four sensor spectral resolutions – namely WorldView-2, Quickbird, RapidEye, and Sentinel-2. In each case, the Random Forest algorithm was used to classify the 2013 resampled spectra to represent the three identified disease severity categories. Classification accuracy was evaluated using an independent test dataset obtained during the 2014 growing season. Results showed that Sentinel-2 achieved the highest overall accuracy (84%) and kappa value (0.76), while the WorldView-2, produced slightly lower accuracies. The 608 nm and 705nm were selected as the most valuable bands in detecting the GLS for Worldview 2, and Sentinel-2. Overall, the results imply that opportunities exist for developing operational remote sensing systems for detection of maize disease. Adoption of such remote sensing techniques is particularly valuable for minimizing crop damage, improving yield and ensuring food security.

Made available in DSpace on 2015-03-26T13:37:41Z (GMT). No. of bitstreams: 1 texto completo.pdf: 330706 bytes, checksum: 9be020e5be4feef0a4967a862388b2b0 (MD5) Previous issue date: 2009-10-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / To base the cultivation of Cylindrocladium pteridis and inoculation of the fungus under controlled conditions, was evaluated in this study sporulation in culture, conidial germination, mycelial growth and defoliation of eucalyptus at different temperatures. In preliminary experiments, we evaluated the effect of light and incubation time on germination of conidia. The presence of continuous light significantly reduced germination, resulting in higher germination of conidia in the dark. In assessing the germination under different incubation periods, it was observed that the germination of C.pteridis is very fast, and obtained 100% conidia germinated after 4 h of incubation. In assessing the germination under different temperatures, the optimum for germination was 25 ° C (84.6%). The mycelial growth also varied with temperature, and the maximum was 25 ° C. Aiming to solve the problem of low production of conidia in vitro were evaluated three methods of sporulation of C. pteridis in culture. We compared three methods, and the method of scraping the aerial mycelium followed by flood water was the most sporulation in media AVDA, MEA, PDA and GAA, after 10 days of incubation. We obtained the greatest number of conidia on PDA, with an average of 14.13 x 104 conidia / mL. With half SNA was no significant difference between the methods studied. Subsequently, to study the effect of temperature on leaf eucalyptus, is inoculated plants were kept in a moist chamber at 18, 26, 28 and 30 º C. After 48 h, were transferred to a greenhouse (25 ± 5 º C). The temperature significantly influenced the leaf classes in the base of the crown 50 days after inoculation, and the highest percentage of defoliation occurred at 26 º C. / A fim de embasar o cultivo de Cylindrocladium pteridis e a inoculação do fungo em condições controladas, avaliou-se neste trabalho a esporulação em cultura, a germinação de conídios, o crescimento micelial e a desfolha causada em eucalipto sob diferentes temperaturas. Em experimentos preliminares, avaliou-se o efeito da luminosidade e o tempo de incubação na germinação de conídios. A presença de luz contínua reduziu significativamente a germinação, obtendo-se maior germinação de conídios no escuro. Ao avaliar a germinação sob diferentes períodos de incubação, observou-se que a germinação de C.pteridis é muito rápida, sendo obtido 100% de conídios germinados após 4 h de incubação. Ao avaliar a germinação sob diferentes temperaturas, o ótimo para germinação foi 25 °C (84,6%). O crescimento micelial também variou com a temperatura, e o máximo foi a 25 ºC. Objetivando-se solucionar o problema da baixa produção de conídios in vitro, avaliaram-se três métodos de esporulação de C. pteridis em cultura. Compararam-se três métodos, e com o método de raspagem do micélio aéreo seguido de inundação em água obteve a maior esporulação do fungo nos meios AVDA, MEA, BDA e GAA, após 10 dias de incubação. Obteve-se a maior produção de conídios em BDA, com média de 14,13 x 104 conídios/mL. Com o meio SNA não houve diferença significativa entre os métodos estudados. Posteriormente, para se estudar o efeito da temperatura na desfolha em eucalipto, inocularam-se plantas que foram mantidas em câmara úmida a 18, 26, 28 e 30 ºC. Após 48 h, foram transferidas para casa de vegetação (25±5 ºC). A temperatura influenciou significativamente a desfolha em ramos da base da copa aos 50 dias após inoculação, e o maior percentual de desfolha ocorreu a 26 ºC.

Made available in DSpace on 2016-12-08T16:44:38Z (GMT). No. of bitstreams: 1 PGPV08MA071.pdf: 1225933 bytes, checksum: cac05331f9f8408e3041c9d8b75dd641 (MD5) Previous issue date: 2008-06-27 / In this work were used 3 isolates of C. gloeosporioides from different apple producer places, and 245 access belong to the Active Germoplasm Banc Apple Tree Estação Experimental da EPAGRI de Caçador, Santa Catarina . Among the tested access, 185 were resistant and 32 susceptible. From those susceptible, there was not difference in the severity degree of the MFG attack. The data obtained in this study can help in the choice of resistant access, what could be used like parentage in the genetic breeding programs of the apple tree, in order to obtain the resistance to this pathogen.The genetic diversity characterization of the access by means of molecular marker studies, has been used like an important tool to maximize the maintenance work of the germoplasm banks. In this way, the objective of this study was characterize genetically the active germoplasm bank of the apple tree making use of 12 primers of SSR. The analysis of genetic diversity was realized through the DNA extraction of the 169 access, using young leafs. The extraction protocol used was the CTAB, and the estimation of the DNA concentration was done in agarose gel 0,8% coloured with bromide ethidium (0,3 μg/ml), with DNA Fago Lambda (20, 50, 100 e 200 ng/μl) like pattern. A total of 197 alleles were encountered, and the medium number of alleles by locus of SSR was 16,4. The medium heterozigosity expectation was 84%, and the revealed polimorphism by number of the alleles by locus had a high percentage (82%). The genetic similarity analysis showed two distinct groups. The gotten results had demonstrated the existence of high genetic variability in the bank of germoplasma of apple trees, salient for the raised number of alelos for I lease and high level of heterozigosidade. This knowledge will contribute with the improvement in the efficiency of the identification of combinations that will serve of base for the genetic improvement of the apple tree / No presente trabalho foram utilizados 245 genótipos pertencentes ao Banco de Germoplasma de macieira BGM, da Epagri / Estação Experimental de Caçador - EECd, SC. Para identificar os genótipos portadores de resistência à mancha foliar de glomerela - MFG, doença essa causada principalmente pelo fungo Colletotrichum gloeosporioides. Os genótipos foram inoculados com 3 isolados de C. gloeosporioides provenientes de diferentes regiões produtoras de maçã. Entre os genótipos testados, 187 (76,3%) manifestaram resistência e 58 (23,7%) manifestaram suscetibilidade à MFG. Entre as cultivares suscetíveis, não houve diferença no grau de severidade de ataque da MFG. Os resultados obtidos neste estudo têm, dentre outras, a finalidade de subsidiar os programas de melhoramento genético da macieira na seleção de parentais, objetivando a incorporação de resistência genética à MFG nas futuras novas cultivares. Para caracterizar os genótipos do Banco de Germoplasma de macieiras foram utilizados 12 primers de SSR. A análise de diversidade genética foi realizada através da extração do DNA de 169 genótipos, utilizando-se folhas jovens. O método de extração utilizado foi CTAB e a estimativa da concentração de DNA extraído foi feita em gel de agarose 0,8% com brometo de etídeo (0,3 μg/ml), tendo como padrão DNA Fago Lambda (20, 50, 100 e 200 ng/μl). Foi obtido um total de 197 alelos, sendo que o número médio de alelos por loco SSR foi de 16,4. A expectativa média de heterozigosidade foi de 84%, o polimorfismo revelado pelo número de alelos por loco teve uma percentagem alta de 82%. Pela análise de similaridade genética foram observados dois grupos. Os resultados obtidos demonstraram a existência de alta variabilidade genética no banco de germoplasma de macieiras, ressaltado pelo elevado número de alelos por loco e alto nível de heterozigosidade. Esse conhecimento contribuirá com a melhora na eficiência da identificação de combinações que servirão de base para o melhoramento genético da macieira

A mancha foliar de Phaeosphaeria em milho (Zea mays L.) tornou-se uma preocupação no Brasil, nos últimos anos, por causa de sua ampla disseminação em áreas de cultivo. Estudos de herança da reação de genótipos de milho a essa doença foliar são necessários para dar suporte aos programas de melhoramento. Assim, o objetivo desta pesquisa foi mapear QTLs para estudar a herança e para identificar alelos favoráveis de reação à mancha foliar de Phaeosphaeria em uma população de milho tropical. Linhagens endogâmicas L 14- 04B e L 08-05F, altamente susceptível e altamente resistente à mancha foliar de Phaeosphaeria, respectivamente, foram utilizadas para gerar uma população F2. Duzentas e cinqüenta seis plantas F2 foram genotipadas com 143 marcadores microssatélites, e suas progênies F2:3 foram avaliadas em látices simples, 16 x 16, delineados em três estações experimentais, no ano agrícola de 2002/2003, e em quatro estações experimentais no ano agrícola de 2003/2004. A infecção artificial não foi usada, mas parcelas com o parental susceptível L-14-04B foram alocadas no início e no final de cada repetição, a cada dezesseis progênies, e como bordadura ao redor dos experimentos, para propiciar a disseminação dos esporos de P. maydis. Foram avaliadas dez plantas por parcela, aos 30 dias após o florescimento, por escala de notas de 1 (altamente resistente) a 9 (altamente susceptível). As médias de parcelas foram utilizadas para as análises de variância, e as médias dos ambientes foram usadas para mapear QTLs. A metodologia de mapeamento por múltiplos intervalos (MIM) foi utilizada para mapear QTLs. A análise de variância conjunta mostrou alta significância para as progênies e para a interação progênies x ambientes, mas a estimativa da variância genética foi significativamente maior que a estimativa da interação genética x ambientes, e o coeficiente de herdabilidade, no sentido amplo, foi alto (91,37%). Seis QTLs foram mapeados, um para cada dos seguintes cromossomos: 1 (Ph1), 3 (Ph3), 4 (Ph4), e 6 (Ph6); e dois para o cromossomo 8 (Ph8a e Ph8b). O grau médio de dominância foi de dominância parcial, mas a ação gênica dos QTLs variou de aditiva a dominância parcial, e a epistasia do tipo dominante x dominante foi também detectada entre os QTLs mapeados do cromossomo 8. A variância fenotípica, explicada pelos QTLs ( 2 R ), variou de 2,91% (Ph8b) a 11,86% (Ph8a), e os efeitos conjuntos dos QTLs explicaram 41,62% da variância fenotípica. Todos os alelos favoráveis para a reação à mancha de Phaeosphaeria; por exemplo, alelos de resistência, estavam na linhagem parental resistente L-08-05F. A correlação entre os valores de médias fenotípicas e os valores genotípicos preditos, baseados nos efeitos de QTLs das progênies, foi 70 , 0 = r ; a seleção, baseada em ambos os critérios (médias fenotípicas e valores preditos) para a intensidade de seleção de 10% (26 progênies) mostrou concordância de somente 46,15% (12 progênies). Todavia, os alelos favoráveis dos QTLs, mapeados da linhagem parental resistente L-08-05F, poderão ser transferidos para outras linhagens em programas de melhoramento via retrocruzamentos assistidos por marcadores moleculares, os quais poderão ser úteis para o melhoramento. / Phaeosphaeria leaf spot disease in maize (Zea mays L.) has becoming a concern in Brazil in the last years because of its increase spreading in maize growing areas. Inheritance studies of the reaction of maize genotypes to this foliar disease are necessary to support plant breeding programs. Thus, the objective of this research was to map QTLs to study the inheritance and to identify favorable alleles for reaction to the Phaeosphaeria leaf spot in a tropical maize population. Inbred lines L 14-04B and L 08-05F, highly susceptible and highly resistant to Phaeosphaeria leaf spot, respectively, were used to develop an F2 reference population. Two-hundred and fifty-six F2 plants were genotyped with 143 microsatellites markers, and their F2:3 progenies were evaluated in 16 x 16 simple lattice designs at three locations in the 2002/2003 growing season, and at four locations in the 2003/2004 growing season. Artificial infection was not used, but plots of the highly susceptible parental inbred L 14-04B were allocated at the beginning and at the end of each replication, at each set of sixteen progenies, and as a border all around the experiments, to provide the spread of P. maydis spores. Ten plants were evaluated per plot, 30 days after silk emergence, following a note scale; i.e., from 1 (highly resistant) to 9 (highly susceptible). The plot means were used for the analyses of variance, and the least squares means across environments were used to map QTLs. The multiple intervals mapping (MIM) was used for QTL mapping. The joint analysis of variance showed highly significance for progenies and for progenies by environment interaction, but the estimate of genetic variance was significantly greater than the estimate of the genetic by environment interaction, and the broad sense coefficient of heritability was high (91.37%). Six QTLs were mapped, one at each of the following chromosomes: 1 (Ph1), 3 (Ph3), 4 (Ph4), and 6 (Ph6); and two at chromosome 8 (Ph8a and Ph8b). The average level of dominance was partial dominance, but the gene action of the QTLs ranged from additive to partial dominance, and dominance x dominance epistasis was also detected between the QTLs mapped at chromosome 8. The phenotypic variance explained by the QTLs ( 2 R ) ranged from 2.91% (Ph8b) to 11.86% (Ph8a), and the joint QTLs effects explained 41.62% of the phenotypic variance. All the favorable alleles to reaction to Phaeosphaeria leaf spot; i.e., resistance alleles, were in the resistant parental line L- 08-05F. The correlation between mean phenotypic values and the predicted genotypic values based on QTLs effects of the progenies was 70 , 0 = r ; and the selection based under both criteria (phenotypic means and predicted values) at 10% selection intensity (26 progenies) showed an agreement of only 46.15% (12 progenies). Nonetheless, the favorable alleles of the QTLs mapped in the parental line L 08-05F could be transferred to other inbred lines by marker-assisted backcross breeding programs, which could make them useful for breeding purposes.

<p>Frogeye leaf spot (FLS) is a foliar disease in soybean (<i>Glycine max</i> (L.) Merr.) caused by the fungal pathogen <i>Cercospora sojina</i> Hara. FLS is commonly found in hot and humid regions of the southern United States but has become more common in the North Central states. Foliar application of quinone outside inhibitor (QoI) fungicides has been one of the major tools used in the management of this disease, but QoI-resistant <i>C. sojina</i> isolates have been already confirmed in 21 states, including Indiana. We hypothesized that resistant populations of <i>C. sojina</i> to QoIs fungicides are widespread in Indiana and that sexual reproduction is occurring within <i>C. sojina</i> populations, likely contributing to the dissemination of fungicide resistance. The main objectives of this research were to determine the distribution of QoI-resistant <i>C. sojina</i> isolates on soybean from Indiana and to evaluate <i>C. sojina </i>populations for potential sexual reproduction. In the summer of 2019 and 2020, 406 isolates of <i>C. sojina </i>were collected from 32 counties across Indiana and screened for QoI-fungicide resistance using a PCR-RFLP method. An i<i>n vitro </i>fungicide sensitivity test was performed on a subset of isolates to evaluate the sensitivity of <i>C. sojina</i> isolates to azoxystrobin, pyraclostrobin, picoxystrobin, and prothioconazole. A discriminatory dose of picoxystrobin (QoI) and prothioconazole (demethylation inhibitor- DMI) were established at 1 μg/ml and 10 μg/ml, respectively, to distinguish between QoI-resistant and sensitive isolates and to identify a reduction in sensitivity to DMI fungicides, respectively. Discriminatory doses were estimated by testing five concentrations (0.001, 0.01, 0.1, 1, and 10 µg/ml) of each fungicide. QoI-resistant isolates were found in 29 out of the 32 counties. Two hundred and fifty-one (251) out of the 406 isolates (61.8%) were confirmed as QoI-resistant. Partial nucleotide sequences of the cyt <i>b</i> gene from four resistant and four sensitive <i>C. sojina</i> isolates corroborated the presence and absence of the G143A mutation, respectively. Results from the sensitivity assays with azoxystrobin and pyraclostrobin discriminatory doses supported the findings from the PCR-RFLP assay as all QoI-resistant mutants were inhibited less than 50% when exposed to these doses. Results from this study indicated that QoI-resistant <i>C. sojina</i> isolates are spread throughout Indiana and that prothioconazole (DMI) could be a potential supplemental or alternative fungicide to control FLS. Additionally, mating type distribution was determined in 43 <i>C. sojina</i> populations for assessment of potential sexual reproduction. Fifteen (15) populations did not deviate significantly from the expected 1:1 ratio, suggesting potential for cryptic sexual reproduction in these populations, but further research on genetic diversity is required to verify these results. </p> <p> </p>

This research addressed the effects of cultural management practices, cultivar selection, and applications of seasonal fungicides on ultradwarf bermudagrass health and playability and occurrence of foliar diseases. Additionally, novel ectotrophic root-infecting fungi were isolated from ultradwarf bermudagrass roots exhibiting symptoms of summer decline, identified via multilocus phylogenetic analyses, and characterized by morphological assessments and pathogenicity evaluations.

A incidência e severidade da mancha de cercospora, causada por Cercospora zeae-maydis Tehon & Daniels, aumentou significativamente em território brasileiro a partir do ano 2000, sendo hoje considerada uma das principais doenças foliares da cultura do milho. Mesmo assim, poucos estudos com este patossistema foram realizados no Brasil. Este trabalho teve por objetivo determinar meio de cultura e regime luminoso para adequada esporulação de C. zeae-maydis, estudar a reação de um grupo de 118 linhagens endogâmicas de milho quanto a resistência ao patógeno em dois ambientes distintos (Indianópolis-MG e Jardinópolis-SP), observar aspectos microscópicos da esporulação, germinação e penetração em hospedeira suscetível e avaliar diferenças morfológicas, genéticas e de agressividade entre isolados coletados na região centro-sul do país. Os resultados indicaram que a melhor esporulação do fungo foi obtida em meio V8 e suco de tomate temperado quando submetidos a fotoperíodo 12/12h (luz/escuro). Quanto a reação das linhagens à doença, foi possível verificar interação diferencial significativa entre genótipo de milho e os dois ambientes, indicando que fatores ambientais ou patogênicos, distintos entre os locais, podem ter contribuído para os discrepantes comportamentos de alguns genótipos. Também foi possível verificar elevado nível de resistência em 12 linhagens em ambos locais, demonstrando a existência de genótipos mais estáveis para resistência com possibilidade de uso em programas de melhoramento da cultura. Através da análise do padrão de restrição gerado pela digestão da região ITS-5.8S do rDNA, de 104 locos AFLP e de mensurações morfométricas dos conídios, foi possível verificar a existência de dois grupos geneticamente distintos de C. zeae-maydis em território brasileiro. Estes são relatados na literatura como grupos I e II ou espécies afins (siblings species). Estes grupos foram detectados em todos os locais de coleta do território brasileiro, com exceção de Goiás, onde o grupo I não foi observado. Quanto aos aspectos microscópicos deste patógeno, foi possível verificar que sob condições ambientais adequadas a germinação dos esporos ocorre 13 horas após o contato do esporo com a hospedeira, e a penetração, via estômato, tem início 16 horas após a inoculação. Também foi observado o fenômeno da conidiação microcíclica nos isolados brasileiros. Vinte e seis por cento daqueles pertencentes ao grupo I produziram microconídios, enquanto nenhum do grupo II apresentou esta característica. Deste modo, este é o primeiro relato da existência deste fenômeno no grupo I e ausência no grupo II. Estes estudos demonstram que a população brasileira de C. zeae-maydis se assemelha àquelas existentes nos Estados Unidos e na África, com a prevalência dos dois grupos genéticos. / The incidence and severity of cercospora leaf spot, caused by Cercospora zeae-maydis Tehon & Daniels, increased significantly in Brazil in 2000, being considered today one of the major leaf disease of the crop. Despite this, few researches about the pathosystem come being carried in Brazil. The aims of this work were to identify the suitable culture media and light conditions for sporulation of C. zeae-maydis; to study the reaction of 118 mayze genotypes to pathogen in two different locations (Indianópolis - Minas gerais State and Jardinópolis - São Paulo State); to observe some microscopical aspects of esporulation, germination and penetration in a susceptible maize genotype; and finally to assess morphological and genetic differences among a group of isolates collected in center-south Brazil. The results showed that the better culture media for esporulation was the V8 media and tomato juice, under 12-hours photoperiod. Concerning to genotype reaction to disease, it was possible to verify significant interaction between genotypes and environment, indicanting that environmental or pathogenic factors, distinct between locations, may have influenced the reactions of some genotypes. It was possible to identify highly level of resistance in 12 lines in both places, evidencing the existence of stable genotypes that can be used in breeding programs. Analysis of restriction fragments from ITS-5.8S of rDNA, 104 AFLP loci, and conidial measurements, showed the existence of two genetically divergent groups of C. zeae-maydis in Brazil. These groups are similar to the ones reported previously reported as I and II groups or siblings species. Both groups were detected in all sampled regions, except Goiás State where no isolates from group I were detected. Concerning to microscopic traits, it was possible to verify that the brazilian isolates of this pathogen have the ability for production of microconidia. Twenty six percent of the isolates of the group I produced microconidia, while none of the group II showed this trait. Thus, this is the first report with presence of MC in the group I but absence in the group II. The results showed that Brazilian isolates are very similar to isolates from USA and Africa, occurring both genetic groups.

Xanthomonas citri subsp. malvacearum é o agente causal da mancha angular do algodoeiro, uma importante doença reportada em áreas de produção no Brasil e em todo o mundo. A partir da análise comparativa de sequências parciais do gene rpoB de linhagens de X. citri subsp. malvacearum, X. campestris pv. campestris, X. axonopodis pv. axonopodis e X. citri subsp. citri, desenhou-se o par de primers xam1R/2R. Foram testadas 19 espécies pertencentes ao gênero Xanthomonas, além de bactérias dos gêneros Acidovorax, Burkholderia, Erwinia, Pseudomonas e Ralstonia, e o produto de PCR específico de aproximadamente 560 pares de bases foi observado apenas para linhagens de X. citri subsp. malvacearum. Os primers desenhados mostraram-se altamente sensíveis, apresentando níveis de detecção de 8 ufc/ 5,0 L para suspensões da cultura pura da bactéria e 1,0 ng de DNA genômico de X. citri subsp. malvacearum. No isolamento, a partir de amostras de sementes sabidamente contaminadas, foram obtidas colônias bacterianas com características de morfologia e coloração semelhantes à X. citri subsp. malvacearum. Esses isolados foram submetidos a testes de coloração de Gram, hidrólise de amido, reação de hipersensibilidade (HR) em folhas de fumo e tomateiro, testes de patogenicidade em plantas de algodoeiro, amplificação com os primers específicos desenhados e sequenciamento do fragmento obtido e os resultados obtidos confirmaram a identificação dos mesmos como X. citri subsp. malvacearum. Experimentos combinados de BIO-PCR/nested-PCR foram realizados a partir do material obtido do processo de extração do patógeno das sementes contaminadas utilizando-se na primeira etapa de amplificação os primers correspondentes à parte do gene rpoB e na segunda etapa o produto da primeira amplificação e os primers específicos xam1F/2R. O resultado foi a observação de uma banda de aproximadamente 560 pb correspondente ao fragmento específico de X. citri subsp. malvacearum para todas as amostras testadas. Neste trabalho foi desenvolvido um teste de PCR específico para a detecção e identificação rápida e precisa dessa bactéria em amostras de sementes de algodoeiro. / Xanthomonas citri subsp. malvacearum is the causal agent of angular leaf spot of cotton an important disease reported in production areas in Brazil and worldwide. From the comparative analysis of partial rpoB gene sequences of X. citri subsp. malvacearum, X. campestris pv. campestris, X. axonopodis pv. axonopodis and X. citri subsp. citri strains, the pair of primers xam1F/2R was designed. Nineteen species of the genus Xanthomonas and isolates of the genera Acidovorax, Burkholderia, Erwinia, Pseudomonas and Ralstonia were tested and the specific PCR product of about 560 base pairs was observed only for strains of X. citri subsp. malvacearum. The primers were highly sensitive, with detection levels of 8 cfu/ 5.0 L for suspensions of pure culture of bacteria and 1.0 ng of genomic DNA of X. citri subsp. malvacearum. From contaminated seed samples, bacterial colonies were obtained with characteristic morphology and coloration similar to X. citri subsp. malvacearum. These isolates were tested for Gram stain, starch hydrolysis, hypersensitivity reaction (HR) on tobacco and tomato leaves, pathogenicity tests on cotton plants, amplification with the specific primers designed and sequencing of the fragment obtained. The results confirmed their identification as X. citri subsp. malvacearum. PCR experiments in combination of BIOPCR/ nested-PCR were performed with the material obtained from the extraction process of pathogen from seeds using in the first step of amplification primers corresponding to part of the rpoB gene and the second step the product of the first amplification and the specific primers xam1F/2R. The result was a band of approximately 560 bp corresponding to the specific fragment of X. citri subsp. malvacearum for all samples tested. In this work, a PCR test for the quick detection and accurate identification of this bacterium in seed samples of cotton were developed.

A cultura do milho (Zea mays L.) apresenta grande importância cultural, social e econômica, tanto no Brasil como no mundo. Entre os fatores que contribuem grandemente para a diminuição de sua produtividade estão as doenças. A mancha de cercospora ou cercosporiose, causada pelo fungo Cercospora zeae-maydis Tehon & Daniels, é uma das principais doenças da cultura em vários países. Uma vez que o uso de híbridos resistentes é a medida mais eficiente para o seu controle, a caracterização e a discriminação de genótipos de milho quanto ao nível de resistência e de isolados do patógeno quanto ao nível de agressividade é uma etapa fundamental de qualquer programa de melhoramento. Isolados de C. zeae-maydis podem ser classificados em dois grupos genéticos, denominados I e II, segundo análise por marcadores AFLP e por restrição da região intergênica espaçadora do rDNA 5.8S. No Brasil, há ocorrência dos dois grupos, mas nos Estados Unidos há uma prevalência do grupo I sobre o grupo II, ao passo que em países do sul da África verifica-se somente a presença de indivíduos do grupo II. Presentemente, não há nenhum relato sistemático sobre diferenças em agressividade entre indivíduos destes grupos. Assim, o objetivo deste trabalho foi avaliar a agressividade de 20 isolados de C. zeae-maydis dos grupos genéticos I e II quando inoculados em um híbrido de milho suscetível e também testar o comportamento de 10 linhagens de milho frente a oito isolados em dois ambientes para verificar a possível presença de interação diferencial entre isolado, linhagem e local. Para tanto, os isolados foram cultivados em sementes de sorgo para produção de inóculo. Sementes colonizadas foram depositadas no cartucho das plantas e as avaliações foram realizadas utilizando-se escalas diagramáticas. No experimento em casa de vegetação foi verificada uma variação em agressividade entre os isolados do grupo genético I, do grupo genético II e entre os grupos. Observou-se ainda que isolados pertencentes ao grupo genético II são, em média, mais agressivos que isolados do grupo genético I. Este é o primeiro relato de diferenças em agressividade entre os grupos genéticos. No experimento em campo não foram observadas diferenças significativas quanto à agressividade dos isolados avaliados em Jardinópolis (SP) e Indianópolis (MG). Entretanto, observou-se forte interação entre linhagens e locais, indicando que o ambiente exerce influência na doença. Dessa forma, recomendam-se avaliações em ambientes diferentes e a utilização de isolados mais agressivos e pertencentes aos dois grupos genéticos a fim de otimizar a discriminação de genótipos de milho com relação à resistência a C. zeae-maydis. / Maize (Zea maydis L.) is of great social, cultural and economical importance in Brazil and in the world. Maize diseases are the main factors that reduce crop yield. Gray leaf spot, caused by the fungus Cercospora zeae-maydis Tehon & Daniels, is one of the most important diseases in many countries. Given that the disease can be controlled by the use of resistant maize hybrids, the characterization and discrimination of maize genotypes according to their level of resistance and of pathogen isolates according to their aggressiveness are fundamental steps in any breeding program. Isolates of C. zeae-maydis can be classified into two genetic groups, named I and II, by analysis with AFLP markers and restriction of the intergenic spacer region of the 5.8S rDNA. In Brazil, both groups occur whereas in the United States isolates from group I prevail and in some South African countries only isolates from group II can be found. Presently, there are no systematic reports on differences in aggressiveness between these groups. Therefore, the objective of this study was to evaluate the aggressiveness of 20 isolates of C. zeae-maydis from both genetic groups when inoculated in a susceptible maize hybrid and also to test the reaction of 10 maize inbreds to eight C. zeae-maydis isolates in two environments in order to assess the possible occurrence of differential interaction between isolates, inbreds, and locations. Isolates were cultivated in sorghum seeds for innoculum production. Colonized seeds were placed into the whorl of the plants and the disease reaction was evaluated using a diagrammatic scale. In the greenhouse experiment significant variation in aggressiveness was observed among isolates of group I, group II and between groups. Also, it was observed that isolates from group II were, on average, more aggressive than isolates from group I. This is the first report on differences in aggressiveness between the two genetic groups of C. zeae-maydis. In the field experiment no significant differences were observed in aggressiveness among isolates evaluated in Jardinópolis (SP) and Indianópolis (MG) for the inbreds tested. However, a strong interaction between reactions of maize inbreds and regions was observed indicating that the environment influences the disease. Thus, evalutions in several locations with aggressive isolates from both groups is recommended in order to optimize the discrimination of maize genotypes regarding their resistance to C. zeae-maydis.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-03-28T19:19:31Z No. of bitstreams: 1 2015 - Fernanda Corr?a de Souza.pdf: 1439461 bytes, checksum: 2ae132a0a7316575d458f10db44101a4 (MD5) / Made available in DSpace on 2018-03-28T19:19:31Z (GMT). No. of bitstreams: 1 2015 - Fernanda Corr?a de Souza.pdf: 1439461 bytes, checksum: 2ae132a0a7316575d458f10db44101a4 (MD5) Previous issue date: 2015-10-08 / CAPES / CNPq / FAPERJ / The tomato crop is subject to attack by diseases of different etiologies, especially the gray leaf spot, caused by Stemphylium sp., which infects the aerial part of the plant and has shown higher incidences and losses in growing areas in recent years. Despite the disease importance, few studies are developed to elucidate the aspects of epidemiology and control of the disease. The use of trials involving pathogen inoculations is essential for carrying out these studies, which requires efficient methods of in vitro multiplication. The aim of this study was to verify the influence of some factors applied during incubation on the mycelial growth and sporulation of the pathogen under controlled conditions. Different culture media (V8 juice agar, tomato juice, PDA, oat, carrot, corn flour, tomato leaf and V8+PDA), temperature (25?C; 25+10?C; 25+15?C; 25+20?C; 25/10?C; 25/15?C; 25/20?C), photoperiods (day/night, respectively, of 0h/24h, 4h/20, 6h/18h, 8h/16h and 12h/12h), luminosity (cool white lamps and black light lamps) and stress types applied to the colony (scratching and UV) were tested. Promising factors were determinate and, after this, the virulence of conidia obtained on the selected system was evaluated. Results indicated the tomato juice and V8 juice agar more favorable for growth and sporulation, respectively. The temperature of 25?C continuous favored mycelial growth and alternation of 25?C (day) and 10?C (night) the sporulation. The growth was more stimulated by 12h light/ 12h dark of photoperiod and the sporulation was higher 6h light/ 18h dark. The different light sources had influence on sporulation and cool white lamps were the most stimulating. Not stressed colonies had better results in conidia production. Thus, the suggested protocol in this study consisted in incubation in V8 juice agar media, alternately temperature of 25?C (day) and 10?C (night), 12h light / 12 h dark photoperiod. The produced conidia in this methodology showed great capacity of infection on tomato plants. / A cultura do tomate est? sujeita ao ataque de doen?as de diferentes etiologias, com destaque para a mancha-de-estenf?lio, causada por Stemphylium sp., que infecta a parte a?rea da planta e tem apresentado maiores incid?ncias e perdas nas ?reas de cultivo nos ?ltimos anos. Apesar da import?ncia desta doen?a, s?o poucos os estudos realizados visando esclarecer aspectos da epidemiologia e controle da doen?a. Para realiza??o desses trabalhos ? fundamental o uso de ensaios que envolvam inocula??es do pat?geno o que requer m?todos eficientes de sua multiplica??o in vitro. O presente trabalho teve o objetivo de avaliar a influ?ncia de alguns fatores sobre o crescimento micelial e esporula??o do pat?geno em condi??es controladas. Diferentes meios de cultura (V8, suco de tomate, BDA, aveia, cenoura, farinha de milho, folha de tomate e V8+BDA), temperatura (25 ?C, 25+10 ?C, 25+15 ?C, 25+20 ?C, 25/10 ?C, 25/15 ?C; 25/20 ?C), fotoper?odo (luz/escuro respectivamente, 0h/24h, 4h/20h, 6h/18h, 8h/16h e 12/12h), luminosidade (l?mpadas brancas frias e l?mpadas de luz negra) e tipos de estresse aplicado ? col?nia (raspagem e comprimento de onda) foram testados. Ap?s a determina??o das melhores combina??es de temperatura, fonte de luz e fotoper?odo avaliou-se a virul?ncia dos con?dios obtidos no sistema selecionado. Os resultados indicaram o meio suco de tomate e V8 como os mais favor?veis ao crescimento e esporula??o respectivamente. A temperatura de 25 ?C cont?nuos favoreceu o crescimento micelial e a altern?ncia de 25 ?C (diurno) e 10 ?C (noturno) a esporula??o. O fotoper?odo 12h luz/12h escuro foi o que mais estimulou o crescimento, j? para esporula??o o estimulo foi maior quando foi oferecido 6h luz/18h escuro. As diferentes fontes de luz utilizadas tiveram influ?ncia marcante na esporula??o, sendo as l?mpadas brancas frias as mais estimulantes. As col?nias que n?o sofreram estresse obtiveram melhores resultados na produ??o de con?dios. Dessa forma, o protocolo sugerido neste trabalho consistiu de inocula??o em meio V8, temperatura alternada de 25 ?C (diurno) e 10 ?C (noturno), fotoper?odo de 6 horas de luz branca/18 horas de escuro. Os con?dios produzidos nesta metodologia apresentam grande capacidade de infec??o de plantas de tomateiro.