Dissertations / Theses on the topic 'Tar spot of corn'

Thesis (PhD)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: Gray leaf spot (GLS) of maize, caused by the fungus Cercospora zeae-maydis, can reduce grain yields by up to 60% and it is now recognized as one of the most significant yield-limiting diseases of maize in many parts of the world. The most sustainable and long-term management strategy for GLS will rely heavily on the development of high-yielding, locally adapted GLS resistant hybrids. Molecular markers could be useful to plant breeders to indirectly select for genes affecting GLS resistance and to identify resistance genes without inoculation and at an early stage of plant development. Only two studies in the USA have examined quantitative trait loci (QTL) association with GLS resistance. The aim of this study was to map GLS resistance genes in a resistant Seed Co LTD, Zimbabwean inbred line. Molecular markers linked to the GLS resistance QTL were identified by using the amplified fragment length polymorphism (AFLP) technique together with bulked segregant analysis. Eleven polymorphic AFLP fragments were identified and converted to sequence-specific PCR (polymerase chain reaction) markers. Eight of the 11 converted AFLP markers were added to the maize marker database of the University of Stellenbosch. Five of the 8 converted AFLP markers were polymorphic between the resistant and the susceptible parent. They were amplified on the DNA of 230 plants of a segregating F2 population and linkage analysis was performed with MAPMAKER/EXP. Two linkage groups consisting of two markers each, with a linkage distance of 10.4 cM (LOD 22.83) and 8.2 cM (LOD 55.41) between the two markers, were identified. QTL mapping with MAPMAKER/QTL confirmed the presence of QTL in both linkage groups. Two publicly available recombinant inbred families (Burr et a/., 1988) were used to localize the converted AFLP markers on the genetic map of maize. The QTL, which were identified with the AFLP markers, were mapped to chromosomes 1 and 5. Another AFLP marker was mapped to chromosome 2 and a further to chromosome 3. To obtain more precise localizations of the QTL on chromosomes 1 and 5, sequence-tagged site markers and microsatellite markers were used. The markers were amplified on the DNA of the 230 plants of the F2 population and linkage analysis was performed with MAPMAKER/EXP. The order of the markers was in agreement with the UMC map of the Maize Genome Database. Interval mapping using MAPMAKERlQTL and composite interval mapping using QTL Cartographer were performed. The QTL on chromosome 1 had a LOD score of 21 and was localized in bin 1.05/06. A variance of 37% was explained by the QTL. Two peaks were visible for the QTL on chromosome 5, one was localized in bin 5.03/04 and the other in bin 5.05/06. Both peaks had a LOD score of 5 and 11% of the variance was explained by the QTL. To test the consistency of the detected QTL, the markers flanking each QTL were amplified on selected plants of two F2 populations planted in consecutive years and regression analysis was performed. Both the QTL on chromosome 1 and the QTL on chromosome 5 were detected in these populations. Furthermore, the presence of a QTL on chromosome 3 was confirmed with these populations. A variance of 8 -10% was explained by the QTL on chromosome 3. In this study, a major GLS resistance QTL was thus mapped on chromosomes 1 and two minor GLS resistance QTL were mapped on chromosomes 3 and 5 using a resistant Seed Co LTD, Zimbabwean inbred line. Markers were identified which could be used in a marker-assisted selection program to select for the GLS resistance QTL.
AFRIKAANSE OPSOMMING: Grys blaarvlek (GBV) van mielies, veroorsaak deur die swam Cercospora zeaemaydis, kan graanopbrengs met tot 60% verlaag en word beskou as een van die vernaamste opbrengs-beperkende siektes wêreldwyd. Die toepaslikste langtermyn stragtegie vir GBV beheer sal wees om plaaslike mieliebasters met hoë opbrengs en GBV weerstand te ontwikkel. Molekulêre merkers kan nuttig deur plantetelers gebruik word om weerstandsgene te selekteer. Seleksie is moontlik in die afwesigheid van inokolum en op 'n vroeë stadium van plant ontwikkeling. Slegs twee vorige studies (in die VSA) het kwantitatiewe-kenmerk-Iokusse (KKL), vir GBVweerstand ondersoek. Die doel van hierdie studie was om die GBV weerstandsgene in 'n weerstandbiedende ingeteelde lyn (Seed Co BPK, Zimbabwe) te karteer. Molekulêre merkers gekoppel aan die GBV weerstands KKL is geïdentifiseer deur gebruik te maak van die geamplifiseerde-fragmentlengte-polimorfisme- (AFLP-) tegniek en gebulkte-segregaat-analise. Elf polimorfiese merkers is geïdentifiseer en omgeskakel na volgorde-spesifieke PKR (polimerase kettingreaksie) merkers. Agt van die elf omgeskakelde AFLP-merkers is by die mieliemerker databasis van die Universiteit van Stellenbosch gevoeg. Vyf van die 8 omgeskakelde AFLP-merkers was polimorfies tussen die bestande en vatbare ouers. Hulle is geamplifiseer op die DNA van 230 plante van 'n segregerende F2-populasie en is gebruik in 'n koppelingstudie met MAPMAKER/EXP. Twee koppelingsgroepe, elk bestaande uit twee merkers, met onderskeidelik koppelingsafstande van 10.4 eM (LOD 22.83) en 8.2 eM (LOD 55.41) tussen die merkers, is geïdentifiseer. KKL-kartering het getoon dat KKL in albei koppelingsgroepe aanwesig is. Twee kommersieël beskikbare, rekombinant-ingeteelde families (Burr et aI., 1988) is gebruik om die omgeskakelde AFLP-merkers op die mielie genetiese kaart te plaas. Die KKL wat met die AFLP-merkers geïdentifiseer is, is gekarteer op chromosome 1 en 5. 'n Verdere AFLP-merker is op chromosoom 2 gekarteer en 'n ander op chromosoom 3. Ten einde die KKL op chromosome 1 en 5 meer akkuraat te karteer, is volgordege- etikeerde en mikrosatelliet merkers gebruik. Die merkers is geamplifiseer op die DNA van die 230 plante van die F2-populasie en koppelings-analises is uitgevoer. Die volgorde van die merkers was dieselfde as die van die UMC-kaart in die Mielie Genoom Databasis. Interval kartering met MAPMAKER/QTL en komposiet interval kartering met QTL Cartographer is uitgevoer. Die KKL op chromosoom 1 het 'n LOD-telling van 21 gehad en is in bin 1.05/06 geplaas. Die KKL was verantwoordelik vir 37% van die variansie. Twee pieke was onderskeibaar vir die KKL op chromosoom 5, een in bin 5.03/04 geleë en die ander in bin 5.05/06. Elke piek het 'n LOD-telling van 5 gehad en die twee KKL was verantwoordelik vir 11% van die variansie. Om die herhaalbaarheid van die effek van die KKL te toets is die merkers naaste aan elke KKL geamplifiseer op geselekteerde plante van twee F2-populasies wat in opeenvolgende jare geplant is. Regressie analise is op die data gedoen. Beide die KKL op chromosoom 1 en die KKL op chromosoom 5 kon in hierdie populasies geïdentifiseer word. Verder kon die aanwesigheid van 'n verdere KKL op chromosoom 3 in hierdie populasies bevestig word. Laasgenoemde KKL was verantwoordelik vir 8-10% van die totale variansie. In hierdie studie is daar dus 'n hoof GBV-weerstands KKL gekarteer op chromosoom 1 en twee kleiner GBV-weerstands KKL gekarteer op chromosome 3 en 5. Merkers is geïdentifiseer wat moontlik in merker-gebaseerdetelingsprogramme gebruik kan word om plante te selekteer wat die GBVweerstands KKL het.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O milho é uma das culturas mais extensamente cultivadas em todo mundo. A incidência e a severidade de doenças têm aumentado significativamente nos últimos anos acarretando perdas no rendimento e afetando a qualidade dos grãos. Muitos trabalhos têm sido desenvolvidos na tentativa de identificar híbridos resistentes às principais doenças que acometem a cultura do milho, mas poucos são os relatos de estudos com linhagens. Dessa forma, o objetivo deste estudo foi: 1) identificar linhagens resistentes e susceptíveis com base na área abaixo da curva de progresso de doenças (AACPD) para os sintomas de ferrugem tropical (TR), ferrugem polissora (SR), cercosporiose (GLS), helmintosporiose (NLB), mancha marrom (PBS) e mancha branca (PLS); 2) identificar linhagens resistentes e suscetíveis com base nos parâmetros de adaptabilidade e estabilidade fenotípica para os sintomas de cercosporiose, helmintosporiose, mancha marrom e mancha branca; 3) identificar as melhores datas de semeadura, com a maior ocorrência das doenças, para fins de avaliação de linhagens e outros genótipos para resistência. Cinquenta linhagens, derivadas de populações com grãos flint e dent, foram avaliadas em blocos casualizados com três repetições, aos 45, 60, 75 e 90 dias após a semeadura em duas épocas, para medição da AACPD. Para a análise de adaptabilidade e estabilidade, 41 linhagens foram avaliadas em blocos casualizados com três repetições, 30 dias após o florescimento feminino, em onze épocas de semeadura, usando o método de análise de regressão. Foram atribuídas notas de 1, 2, 3, 4, 5, 6, 7, 8 e 9 correspondendo a 0, 1, 10, 20, 30, 40, 60, 80 e > 80% de área foliar com sintomas de doença. Para a AACPD, a análise de variância conjunta foi significativa para TR, SR, GLS e PLS e a interação linhagens x épocas foi significativa para ferrugem tropical e polissora. Para GLS e NLB as 41 linhagens foram classificadas como resistentes, sendo que as maiores severidades de doenças ocorreram nas semeaduras entre Junho e Setembro. As linhagens IVF1-3, IVF1-7, IVF1 -9, IVF1-10, IVF1 -11, IVF1 -25, IVF1-230, IVD1-2, IVD1 -2-1, IVD1-3, IVD1-9, IVD1 -12, 2F, 3F, 6F, 9F, 10F, 4C, 2D e 7D foram classificadas como resistentes para as doenças estudadas, sendo indicadas para o desenvolvimento de sintéticos. Para a mancha marrom e mancha branca, as semeaduras de Abril, Junho, Julho e Agosto apresentaram maiores severidades de doenças. As linhagens IVD1-9, IVD1-10, 7D, 10D e 2F podem ser indicadas no desenvolvimento de sintéticos resistentes.
Corn is one of the most widely cultivated crops in the worldwide. The incidence and severity of diseases affecting crops have increased significantly in the past years, leading to yield losses and affecting grain quality. Many studies have been carried out with the attempt to identify hybrids that are resistant to the main diseases, but few reports have studied inbred lines. Therefore, the objectives of this study were: 1) identify resistant and susceptible inbred lines based on the area under disease progress curve (AUDPC) for tropical rust, southern rust, gray leaf spot, northern leaf blight, physoderma brown spot and phaeosphaeria leaf spot; 2) identify resistant and susceptible inbred lines based on adaptability and stability parameters for symptoms of gray leaf spot (GLS), northern leaf blight (NLB), physoderma brown spot (PBS) and phaeosphaeria leaf spot (PLS); 3) identify the best planting dates, with the highest occurrence of diseases, for the purpose of evaluating inbred lines and other genotypes for resistance. For AUDPC, fifty inbred lines, derived from populations with flint and dent grains, were evaluated in randomized block designs with three replications, at 45, 60, 75 and 90 days after planting in two seasons. For the analysis of adaptability and stability, forty-one inbred lines were evaluated in randomized blocks with three replications, 30 days after silking, in eleven planting dates, using regression analysis method. The scale of scores from 1, 2, 3, 4, 5, 6, 7, 8 and 9 corresponding to 0, 1, 10, 20, 30, 40, 60, 80 and > 80% of leaf area with disease symptoms was used. For AUDPC, the joint analysis of variance was significant for TR, SR, GLS and PLS, while the interaction inbred lines x environments, was significant for TR and SR. For GLS and NLB, forty-one inbred lines were classified as resistant and the highest severities of diseases occurred in planting dates between June and September. The inbred lines IVF1-3, IVF1-7, IVF1 -9, IVF1-10, IVF1 -11, IVF1 -25, IVF1-230, IVD1-2, IVD1 -2-1, IVD1-3, IVD1-9, IVD1 -12, 2F, 3F, 6F, 9F, 10F, 4C, 2D and 7D were classified as resistant to the diseases studied and are indicated to produce synthetics. For PBS and PLS, the plating dates of April, June, July and August showed higher disease severity. The inbred lines IVD1-9, IVD1-10, 7D,10D and 2F may be indicated to produce synthetics.

Orientador: João Antonio da Costa Andrade
Resumo: O milho é uma das culturas mais extensamente cultivadas em todo mundo. A incidência e a severidade de doenças têm aumentado significativamente nos últimos anos acarretando perdas no rendimento e afetando a qualidade dos grãos. Muitos trabalhos têm sido desenvolvidos na tentativa de identificar híbridos resistentes às principais doenças que acometem a cultura do milho, mas poucos são os relatos de estudos com linhagens. Dessa forma, o objetivo deste estudo foi: 1) identificar linhagens resistentes e susceptíveis com base na área abaixo da curva de progresso de doenças (AACPD) para os sintomas de ferrugem tropical (TR), ferrugem polissora (SR), cercosporiose (GLS), helmintosporiose (NLB), mancha marrom (PBS) e mancha branca (PLS); 2) identificar linhagens resistentes e suscetíveis com base nos parâmetros de adaptabilidade e estabilidade fenotípica para os sintomas de cercosporiose, helmintosporiose, mancha marrom e mancha branca; 3) identificar as melhores datas de semeadura, com a maior ocorrência das doenças, para fins de avaliação de linhagens e outros genótipos para resistência. Cinquenta linhagens, derivadas de populações com grãos flint e dent, foram avaliadas em blocos casualizados com três repetições, aos 45, 60, 75 e 90 dias após a semeadura em duas épocas, para medição da AACPD. Para a análise de adaptabilidade e estabilidade, 41 linhagens foram avaliadas em blocos casualizados com três repetições, 30 dias após o florescimento feminino, em onze épocas de semeadura, us... (Resumo completo, clicar acesso eletrônico abaixo)
Doutor

Gray leaf spot, caused by Cercospora zeae-maydis, can be a yield-limiting factor in maize where continuous minimum tillage practices are followed. Commercial corn hybrids were evaluated for response to gray leaf spot for seven years at two Virginia locations (Shenandoah and Wythe Counties) and one year at a third location in Virginia (Montgomery County). Yield losses, when comparing resistant to susceptible classes, were approximately 2,000 kg ha⁻¹ at Wythe County in 1982, 750 kg ha⁻¹ at Shenandoah County in 1984, and 2,150 kg ha⁻¹ at Montgomery County in 1988. The inheritance of reaction to gray leaf spot was studied using a 14 inbred diallel in Montgomery and Wythe Counties, Virginia in 1987 and 1988 planted in randomized complete block designs. Resistance was found to be highly heritable and controlled by additive gene action. Inbreds producing high yielding, resistant, and agronomically superior hybrids were identified (B68, NC250, Pa875, Va14, Va17, and Va85); and several hybrids between these lines had high levels of resistance, high yield, and good general agronomic characters (B68 x KB1250, KB1250 x Pa875, and NC250 x Pa875). Currently available inbreds could be used to produce hybrids with higher levels of resistance than hybrids currently available to growers, and these could serve as a basis for gray leaf spot breeding programs. Lesion size measurements were not correlated with disease scores. Late-season photosynthesis rates were associated positively with resistance. The hybrids of some inbreds were found to produce high levels of pigment (believed to be anthocyanins) around the gray leaf spot lesions. These did not limit the size of the individual lesion later in the season. Some pigment(s)-producing genotypes were found to be resistant when the pigment character was expressed. This type of resistance must prevent or inhibit infection of the leaf but not later colonization, once established. Maize dwarf mosaic virus (MDMV) also limits maize production in some areas where johnsongrass (Sorghum halepense L.) is a problem. Resistance to MDMV was found to be mainly additive and highly heritable. However, a strong specific combining ability component was found, indicating that the background of the material receiving resistance genes may have a strong effect on the expression of resistance. Inbreds capable of producing high-yielding, resistant, and agronomically acceptable hybrids are available (B68, NC250, A632, Pa875, Va17, and Va85); and several hybrids between these lines have high levels of resistance, high yield, and good general agronomic characters (B68 x KB1250, KB1250 x Pa875, and NC250 x Pa875).
Ph. D.

Gasification is a process used to convert any carbonaceous species through heterogeneous reaction to obtain the desired gaseous products of H2 and CO which are used to make chemicals, liquid transportation fuels, and power. Both pyrolysis and heterogeneous gasification occur in commercial entrained-flow gasifiers at pressures from 4 to 65 atm with local gas temperatures as high as 2000 °C. Many gasification studies have been performed at moderate temperatures, heating rates, and pressures. In this work, both pyrolysis and char gasification experiments were performed on coal, petroleum coke, and biomass at conditions pertinent to commercial entrained-flow gasifiers. Rapid biomass pyrolysis experiments were performed at atmospheric pressure in an entrained-flow reactor for sawdust, switchgrass, corn stover, and straw mostly using a peak gas temperature of 1163 K at particle residence times ranging from 34 to 113 ms. Biomass pyrolysis was modeled using the Chemical Percolation Devolatilization model assuming that biomass pyrolysis occurs as a weighted average of its individual components (cellulose, hemicellulose, and lignin). Thermal cracking of biomass tar into light gas was included using a first-order model with kinetic parameters regressed in the current study. Char gasification rates were measured for biomass, petroleum coke, and coal in a pressurized entrained-flow reactor at high heating-rate conditions at total pressures between 10 and 15 atm. Peak centerline gas temperatures were between 1611 and 1879 K. The range of particle residence times used in the gasification experiments was 42 to 275 ms. The CO2 gasification rates of biomass and petroleum coke chars were measured at conditions where the reaction environment consisted of approximately 40 and 90 mol% CO2. Steam gasification rates of coal char were measured at conditions where the maximum H2O concentration was 8.6 mol%. Measured data was used to regress apparent kinetic parameters for a first-order model that describes char conversion. The measured char gasification rates were far from the film-diffusion limit, and are pertinent for pulverized particles where no internal particle temperature gradients are important. The modeling and measured data of char gasification rates in this research will aid in the design and efficient operation of commercial entrained-flow gasifiers, as well as provide validation for both existing and future models at a wide range of temperatures and pressures at high heating-rate conditions.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The main objectives of this work were to identify the causal agent of the maize White Spot, to obtain preliminary information on the disease dispersal in the field and to characterize the reaction of maize hybrids and inbreds to the disease. For the etiological studies, isolations were performed from white spot lesions the anasarca phase, resulting in the development of bacterial colonies. Maize hybrids BRS2022, BRS1010, 1D2195, BRS1040, BRS1035, BRS1031, BRS3025, BRS1030, 2B710 e P30F35 and inbred lines L3, L228-3, 521274, 521236 e 262841-1-4-1 were evaluated under natural epidemic in a randomized block design with three replications. Cultivars were planted in single row plots, separated by two rows of the resistant hybrid BRS1010. Spreader rows were formed by planting the susceptible genotype DAS657 0,5 m apart and in front of each block. Disease severity was evaluated at a weekly internal starting 60 days after planting, through a 1 to 9 scale of disease severity where 1= no disease and 9= 100% of leaf area affected. Ratings were taken at three different locations within each plot: 1, 2, 3, 4, 5 and 6 meters inoculum source. Data were used for the calculation of the area under disease progress curve (AUDPC), disease severity at 50% of epidemic development (Y50), disease severity at the end of the epidemic, and the rate of disease progress. Inoculations on the susceptible hybrid DAS657, in the greenhouse, reproduced the typical symptoms of the disease. Re-isolations from theses lesions confirmed the presence of the same bacteria isolated from the field, which identified as Pantoea ananatis, confirming previous reports on the involvement of this bacteria in the initial lesions of this disease. No disease gradient was observed based on the disease severity observed in each point of evaluation within each plot. A better distinction between the level of resistance of maize genotypes was obtained through AUDPC and Ymáx values. Maize hybrids BRS1030, BRS1035 and BRS1010 and inbreds L3, and L228-3 were the most resistant genotypes. These inbred lines may be useful in breeding programs for resistance to maize white spot.
Este trabalho objetivou confrimar o agente causal da mancha-branca do milho, obter informações preliminares sobre a dispersão do patógeno e caracterizar a reação de genótipos de milho a doença. Para o estudo etiológico, isolados foram obtidos de lesões de manchabranca em fase de anasarca, resultando em desenvolvimento de colônias bacterianas. Híbridos de milho, BRS2022, BRS1010, 1D2195, BRS1040, BRS1035, BRS1031, BRS3025, BRS1030, 2B710 e P30F35 e as linhagens L3, L228-3, 521274, 521236 e 262841-1-4-1 foram avaliados sob epidemia natural em delineamento de blocos ao acaso e três repetições. Os cultivares foram plantados em fileiras de cinco metros, separadas por uma linha do híbrido resistente BRS1010. A cortina suscetível (fonte de inóculo) formada pelo híbrido DAS657, foi plantada na parte frontal de cada bloco, afastada 0,5 m. A severidade da doença foi avaliada em intervalos semanais a partir dos 60 dias do plantio, utilizando uma escala de 1 a 9, onde: 1= sem doença e 9= 100% de área foliar afetada. As avaliações foram realizadas em 6 pontos dentro da parcela afastados 1, 2, 3, 4, 5 e 6 metros da fonte de inóculo. Os dados de severidade foram usados para o calculo da área abaixo da curva de progresso da doença (AACPD), severidade da doença na metade da epidemia (Y50), severidade da doença no final da epidemia (Ymáx), e taxa de progresso da doença. Com inoculações em híbrido suscetível DAS657, em casa de vegetação, foi possível reproduzir os sintomas típicos da doença. Reisolamento a partir dessas lesões confirmou a presença da mesma bactéria isolada do campo, identificada como Pantoea ananatis, corroborando relatos do envolvimento desta bactéria nos sintomas iniciais da doença. Não foi observada a formação de um gradiente de dispersão baseado na severidade da doença observada em cada ponto de avaliação dentro da parcela. A melhor distinção entre os níveis de resistência de genótipos de milho foi obtida pelos valores de AACPD e Ymáx. Os híbridos de milho BRS1030, BRS1035 e BRS1010 e as linhagens L3, e L228-3 foram os genótipos mais resistentes. Essas linhagens podem ser usadas em programas de melhoramento visando resistência a mancha-branca.

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.

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.

L'analyse concurrentielle du marché pertinent du football professionnel européen fait ressortir le saisissant contraste présent entre la force de l'exigence d'une concurrence "libre" et "non faussée" et la relativité de son existence sur le marché. Depuis l'arrêt "Bosman" et la reconnaissance par la Cour de justice de la liberté de circulation des sportifs professionnels, l'économie concurrentielle du marché en cause est inégalitaire et le sort de la compétition économique prévisible. En supprimant les clauses de nationalité, qui limitaient les flux transnationaux de joueurs et l'impact de l'hétérogénéité des systèmes fiscaux sur le processus concurrentiel, les juges de Luxembourg ont structurellement remis en cause les conditions de concurrence du marché. En effet, les clubs au "coin socio-fiscal du travail" élevé ont vu leur liberté concurrentielle être affectée et leur chance de réussir, dans la compétition économique, considérablement se réduire. Leur incapacité fiscale à proposer, à coût égal, des rémunérations attractives et compétitives aux facteurs de concurrence que sont les joueurs, s'est traduite, dans le contexte de la libéralisation du marché, par un "état d'infériorité structurelle". Cette situation immédiatement contraire aux objectifs des Traités a engendré une allocation inefficace des richesses du marché et une qualité disparate de l'offre de spectacle sportif au sein de la Communauté
The competitive analysis of the relevant market of the European professional football highlights the striking contrast between the strength of the requirement of a “free” and “undistorted” competition and the relativity of its existence on the market.Since the “Bosman” decision and the recognition by the European Court of Justice of the freedom of movement for professional sportsmen, the competitive economy of the relevant market is non-egalitarian and the result of economic competition is predictable. By suppressing the nationality clauses which limited the transnational flows of the players and the impact of heterogeneity of tax systems on the competitive process, the judges of Luxembourg structurally altered the competitive conditions into the market. Indeed, football clubs at “the wedge between labour costs and net wages” saw their competitive freedom being affected and their chance to succeed in the economic competition considerably reduced. Their tax incapacity to propose, at equal cost, attractive and competitive payments to the competition factors that are the players, has translated, in the context of the liberalization of the market, by a “structural inferiority state”. This situation at once went against the objectives of the Treaties causing an inefficient allowance of the wealth in the market, as well as an ill-assorted quality of the sport entertainment offer within the Common Market

碩士
國立高雄應用科技大學
國際企業研究所
101
As a clean and pure energy, natural gas has become a valuable product to the industries around the world. This study discusses the multiple relationships (both in a long run and a short run) of natural gas price and corn price, opposed to the fluent studies on the price of oil, and the agricultural commodity price. This paper employs a multivariate E-GARCH model to analyze the price spill-over effect between the natural gas market and corn market based on monthly price ranging from January 1997 to February 2013. Several major results stand out from the research. First, we find there is no long run equilibrium relationship between these two market prices. Second, evidence shows that there is a volatility spillover between natural gas market and corn market. Third, we demonstrate that there is an asymmetric effect between these market prices.

Experiments were performed to determine the nature of maize influence on bean disease in additive-type intercrops. Overall effects of intercrops on angular leaf spot (caused by Phaeoisariopsis griseola) in Kenya indicated >23% reductions (P<0.05) in area under the disease progress curve (AUDPC) in two of three season-site combinations. Fertilization tended to increase disease (135-205%, P<0.10), but changes in bean density or planting pattern had no effect. Intercrops reduced temperature and wind velocity, but increased relative humidity. A 27% AUDPC reduction (P=0.07) in bean rust (caused by Uromyces appendiculatus) due to intercropping was observed in Oregon in 1989 and 1990 in two of three locations. Mechanisms of maize influence on rust were also assessed in Oregon. Intercropping, and competition of maize with beans alone, consistently steepened dispersal gradients (P<0.10). Interference of maize with dispersal alone tended to flatten gradients. Spore retention in plots was increased in mid-season, then decreased late in the season, due to competition in both years (P<0.05). Intercropping reduced infection by 96% late in 1989 (P<0.05), probably due to microclimatic influence of maize. The data from these experiments were used as inputs for computer simulation to evaluate effects of specific mechanisms on disease dynamics. Combination of all mechanisms (= intercrop) reduced AUDPC to 32% of monocrop, using 1989 data. Infection efficiency reductions, and to a lesser extent dispersal effects, were responsible for these changes. Intercrop effects declined as pathogen multiplication rate (DMFR) increased. No intercrop effect occurred at any DMFR using 1990 data, although interference and competition effects of maize alone both increased AUDPC at low DMFR. Partitioning dispersal effects into those due to gradient slope changes and spore retention indicate that the latter accounts almost entirely for disease alteration.
Graduation date: 1992