In the first experiment, forage samples (n = 39) were collected during 4 years (2006 ? 2009) from pastures grazed by Santa Gertrudis cattle at the King Ranch, TX. The in vitro gas production technique (IVGP) was performed to understand the pattern of fermentation parameters of the forage and obtain fractional digestion rate (kd) values to predict total digestible nutrients (TDN). The best nonlinear model to describe the IVGP values of the forages was the two-pool logistic equation. The passage rate (kp) of 4%/h was used.. The kp predicted by the Large Nutrient Ruminant System (LNRS) model was 3.66%/h. The average TDN was 55.9% compared to 53.8% using a theoretical equation. In the second experiment, Brahman bulls (n = 16) grazed Coastal bermudagrass pastures [Cynodon dactylon (L.) Pers.] and stocked at a moderate to low grazing pressure. Three periods of fecal collections were made within each period. Bulls were individually fed at 0700 and 1900 h of 400 g of corn gluten pellets containing C32 n-alkanes. Each period was divided in 2 sub periods in which fecal samples were collected 4 times a day (0700, 1100, 1500 and 1900 h). N-alkanes in the forage and feces were determined using gas chromatography. In the third experiment, four methods were used to estimate dry matter intake (DMI): C31 or C33 with or without adjustment for forage C32 (C31_0 and C33_0, respectively). There was a difference between morning (0700 and 1100 h) and afternoon fecal collections (1500 and 1900 h) on the predicted DMI using C31 (P = 0.0010), C33 (P = 0.0001), C31_0 (P = 0.0010), or C33_0 (P < 0.0001). There was no difference in average daily gain (ADG) between low and high residual feed intake (RFI) (P = 0.5709). The nonparametric analysis indicated that preranking animals for efficiency under confinement conditions does not guarantee (P < 0.0001) similar ranking under grazing conditions when using the alkane technique to determine forage DMI. In order to estimate DMI at least 5 d of fecal collection and 2 times a day of collection (0700 and 1500h) are needed to decrease the variability.

This paper investigates the viability of two different mappings of two parameters of the digital musical instrument Force Ghost. The instrument produces sound by having an  ambience (a recording of rain or of waves on the beach) filtered by bandpass filters  whose center-frequencies are controlled by a midi-keyboard. Five bandpass filters are assigned to each note, corresponding to the fundamental frequency its and its multiples (2f,3f,4f,5f). The mapped parameters are the Q-factor of the bandpass filters and the timbre, defined as the relative level between the even and odd multiples harmonics. These two parameters are mapped to the modulation wheel and the pitch bend wheel. The mappings of the parameters are investigated with the help of musical tasks completed by musicians rounded up with semi-structured interviews. The interviews revealed that the modulation wheel was to be prefered due to the lack of a spring mechanism (which is an attribute of the pitch bend wheel), forcing the wheel back to its default position (in the middle) when released. The results from the musical tasks suggested an indication that none of the sensors have better controllability than the other, regardless of parameter it controls. In conclusion, a sensor that gravitates towards a resting state does not seem to be suitable to control a parameter (scaling) that lacks a “resting value” (as perceived by musicians). / Denna artikel utreder två mappningar av två parametrar hos det digitala musikaliska instrumentet Force Ghost. Instrumentet ljuder genom att en ljudkälla filtreras av bandpassfilter. Ljudkällan i detta fall är ljudet av regnfall i en skog. Varje tangent på ett keyboard är kopplat till minst ett bandpassfilter, vars MIDI-not kopplat till motsvarande frekvens. Denna frekvens är bandpassfiltrets centerfrekvens. När en tangent nedtrycks genereras bandpassfiltret, vilket skapar en ton ur ljudkällan. De två parametrarna i fokus är kopplade till bandpassfiltrerna. De är Q-värdet (kopplat till bandpassfiltrernas bandbredd) och klangfärgen (kopplat till övertonerna; vilka de är och deras amplitudrelation för varje not). Dessa två parametrar är mappade till modulations-hjulet och pitchbend-hjulet. Mappningen av dessa parametrar är undersökt genom musikuppgifter och självständig utforskning genomförda av musiker. Detta spelades in och sedan utfördes en semistrukturerad intervju med musikerna. Intervjuerna visade att modulations-hjulet föredrogs på grund av avsaknaden av fjädermekanismen som finns hos pitchbend-hjulet. Denna mekanism tvingar pitchbend-hjulet tillbaka till sin utgångsposition (i mitten) när den släpps. Resultaten från musikuppgifterna indikerar att ingen av sensorerna har bättre kontrollbarhet än den andre, oavsett vilket parameter den kontrollerar. Sammanfattningsvis, en sensor som graviterar mot ett viloläge verkar inte vara lämplig för att kontrollera en parameter (-skalning) som saknar ett “vilovärde” (så som uppfattat av musiker).

Frogeye leaf spot (FLS), caused by Cercospora sojina Hara, is a foliar disease of soybean (Glycine max (L.) Merr.). FLS has re-emerged as an important disease due to the widespread QoI-resistant fungal population in Mississippi. Growers have transitioned from a stand-alone QoI fungicide to a multi-mode of action fungicide. One disadvantage of certain MOA’s is phytotoxicity. Phytotoxicity is a concern among soybean growers as to whether or not yield is lost. Disease, phytotoxicity, green stem, yield, plant morphology, and grain quality were analyzed to determine the impacts of fungicide phytotoxicity. Yield was significantly and negatively correlated as a result of phytotoxicity. Numerical differences in phytotoxicity severity were observed among all cultivars. Phytotoxicity severity were greatest in the Hornbeck 4950 LL with an average of 26.9%. Tank-mixing dodine with Manniplex B Moly, Megafol, and Veritas decreased phytotoxicity by 8.5, 2.7, 11.4% compared to dodine as a stand-alone treatment, respectively.

A citricultura brasileira se destaca no mercado global de citros, apresentando altos valores de produção e produtividade. Dentre as diversas doenças que afetam a cultura, a podridão floral dos citros (PFC) vem ganhando destaque com o deslocamento de áreas produtoras para regiões mais favoráveis à ocorrência desta doença. A PFC, causada por espécies dos complexos Colletotrichum acutatum e C. gloeosporioides, é especialmente problemática em anos de temperaturas amenas e alta umidade. Os citricultores realizam pulverizações preventivas para o controle da PFC todos os anos, embora condições climáticas favoráveis à doença ocorram apenas ocasionalmente. Além do impacto econômico, as frequentes pulverizações com fungicidas aumentam a pressão de seleção sobre isolados resistentes, o que pode interferir na eficiência do controle químico. A utilização de sistemas de previsão de epidemias pode evitar que pulverizações desnecessárias de fungicidas sejam realizadas caso não haja condições favoráveis à ocorrência da doença. Para o desenvolvimento destes sistemas, é imprescindível determinar um limiar de ação para a aplicação de fungicidas nos pomares. Dessa forma, o presente trabalho teve por objetivos: (i) estabelecer um limiar de ação para a aplicação de fungicidas com base na germinação de conídios de C. acutatum que permita o controle a doença igualmente ou de forma mais eficiente do que o sistema de pulverização adotado pelos citricultores do sudoeste paulista; (ii) caracterizar a sensibilidade de isolados dos complexos C. gloeosporioides e C. acutatum à trifloxistrobina e ao tebuconazol in vitro e molecularmente, para identificar possíveis mudanças de sensibilidade das espécies a estes fungicidas. Para a definição do limiar de ação, tratamentos baseados em índices de risco foram comparados ao tratamento testemunha e ao calendário fixo de aplicações, usualmente adotado pelos produtores. A aplicação de fungicidas quando limiar de 15% de germinação de conídios era atingido, foi eficiente em controlar a doença e reduzir o número de aplicações de fungicidas. Nos ensaios de sensibilidade a fungicidas dois métodos foram utilizados para a determinação da CE50: o da diluição em gradiente espiral para trifloxistrobina e tebuconazol e o da inibição da germinação de conídios para a trifloxistrobina. Foram utilizados isolados coletados entre 1999 e 2016. A CE50 média da coleção de isolados de acordo com o método da diluição em gradiente espiral variou de 0,158 a 0,297 &mu;g/ml e 0,1 a 0,182 &mu;g/ml para trifloxistrobina e tebuconazol, respectivamente. Para a trifloxistrobina, de acordo com o método da inibição da germinação, a CE50 média foi de 0,002 &mu;g/ml. Não foram verificadas características moleculares nem valores de CE50 atrelados à mudança de sensibilidade dos isolados. / Brazilian citrus industry represents a significant share in the global citrus market. Amongst several diseases that affect the crop, postbloom fruit drop (PFD) has been gaining prominence in Sao Paulo with the displacement of citrus areas to regions in which weather conditions are more favorable to the occurrence of this disease. PFD, caused by species of the complexes Colletotrichum acutatum and C. gloeosporioides, is especially problematic in years of mild temperatures and high humidity. Citrus growers spray the orchards preventively for PFD control every year, although favorable climatic conditions do not occur regularly. In addition to the economic impact, this practice increases the selection pressure of fungicide resistant isolates, and may decrease the efficiency of chemical control in a long term. The use of disease forecasting systems is able to prevent unnecessary fungicide sprays. For the development of such systems, it is essential to determine an action threshold for the application of fungicides in the orchards. The objectives of this work were: (i) to establish an action threshold for fungicide sprays based on the germination of C. acutatum conidia; (ii) to characterize the sensitivity of C. gloeosporioides and C. acutatum isolates to trifloxystrobin and tebuconazole in vitro and molecularly. Regarding the definition of the action threshold, treatments based on risk indices were compared to the control treatments and calendar based sprays, usually adopted by growers. The 15% conidia germination threshold was efficient in controlling the disease and reducing the number of fungicide applications. In the fungicide sensitivity tests, two methods were used to determine the EC50, the spiral gradient dilution for trifloxystrobin and tebuconazole, and the method of conidial germination inhibition for trifloxystrobin. Isolates collected between 1999 and 2016 were used. The mean EC50 of the isolate collection determined by the spiral gradient dilution method ranged from 0.158 to 0.297 &mu;g/ml and from 0.1 to 0.182 &mu;g/ml for trifloxystrobin and tebuconazole, respectively. Mean EC50 of trifloxystrobin estimated by the conidial germination inhibition method was 0.002 &mu;g/ml. No mutations or EC50 values indicated shifts of fungicide sensitivity on the isolates.

A citricultura brasileira se destaca no mercado global de citros, apresentando altos valores de produção e produtividade. Dentre as diversas doenças que afetam a cultura, a podridão floral dos citros (PFC) vem ganhando destaque com o deslocamento de áreas produtoras para regiões mais favoráveis à ocorrência desta doença. A PFC, causada por espécies dos complexos Colletotrichum acutatum e C. gloeosporioides, é especialmente problemática em anos de temperaturas amenas e alta umidade. Os citricultores realizam pulverizações preventivas para o controle da PFC todos os anos, embora condições climáticas favoráveis à doença ocorram apenas ocasionalmente. Além do impacto econômico, as frequentes pulverizações com fungicidas aumentam a pressão de seleção sobre isolados resistentes, o que pode interferir na eficiência do controle químico. A utilização de sistemas de previsão de epidemias pode evitar que pulverizações desnecessárias de fungicidas sejam realizadas caso não haja condições favoráveis à ocorrência da doença. Para o desenvolvimento destes sistemas, é imprescindível determinar um limiar de ação para a aplicação de fungicidas nos pomares. Dessa forma, o presente trabalho teve por objetivos: (i) estabelecer um limiar de ação para a aplicação de fungicidas com base na germinação de conídios de C. acutatum que permita o controle a doença igualmente ou de forma mais eficiente do que o sistema de pulverização adotado pelos citricultores do sudoeste paulista; (ii) caracterizar a sensibilidade de isolados dos complexos C. gloeosporioides e C. acutatum à trifloxistrobina e ao tebuconazol in vitro e molecularmente, para identificar possíveis mudanças de sensibilidade das espécies a estes fungicidas. Para a definição do limiar de ação, tratamentos baseados em índices de risco foram comparados ao tratamento testemunha e ao calendário fixo de aplicações, usualmente adotado pelos produtores. A aplicação de fungicidas quando limiar de 15% de germinação de conídios era atingido, foi eficiente em controlar a doença e reduzir o número de aplicações de fungicidas. Nos ensaios de sensibilidade a fungicidas dois métodos foram utilizados para a determinação da CE50: o da diluição em gradiente espiral para trifloxistrobina e tebuconazol e o da inibição da germinação de conídios para a trifloxistrobina. Foram utilizados isolados coletados entre 1999 e 2016. A CE50 média da coleção de isolados de acordo com o método da diluição em gradiente espiral variou de 0,158 a 0,297 &mu;g/ml e 0,1 a 0,182 &mu;g/ml para trifloxistrobina e tebuconazol, respectivamente. Para a trifloxistrobina, de acordo com o método da inibição da germinação, a CE50 média foi de 0,002 &mu;g/ml. Não foram verificadas características moleculares nem valores de CE50 atrelados à mudança de sensibilidade dos isolados. / Brazilian citrus industry represents a significant share in the global citrus market. Amongst several diseases that affect the crop, postbloom fruit drop (PFD) has been gaining prominence in Sao Paulo with the displacement of citrus areas to regions in which weather conditions are more favorable to the occurrence of this disease. PFD, caused by species of the complexes Colletotrichum acutatum and C. gloeosporioides, is especially problematic in years of mild temperatures and high humidity. Citrus growers spray the orchards preventively for PFD control every year, although favorable climatic conditions do not occur regularly. In addition to the economic impact, this practice increases the selection pressure of fungicide resistant isolates, and may decrease the efficiency of chemical control in a long term. The use of disease forecasting systems is able to prevent unnecessary fungicide sprays. For the development of such systems, it is essential to determine an action threshold for the application of fungicides in the orchards. The objectives of this work were: (i) to establish an action threshold for fungicide sprays based on the germination of C. acutatum conidia; (ii) to characterize the sensitivity of C. gloeosporioides and C. acutatum isolates to trifloxystrobin and tebuconazole in vitro and molecularly. Regarding the definition of the action threshold, treatments based on risk indices were compared to the control treatments and calendar based sprays, usually adopted by growers. The 15% conidia germination threshold was efficient in controlling the disease and reducing the number of fungicide applications. In the fungicide sensitivity tests, two methods were used to determine the EC50, the spiral gradient dilution for trifloxystrobin and tebuconazole, and the method of conidial germination inhibition for trifloxystrobin. Isolates collected between 1999 and 2016 were used. The mean EC50 of the isolate collection determined by the spiral gradient dilution method ranged from 0.158 to 0.297 &mu;g/ml and from 0.1 to 0.182 &mu;g/ml for trifloxystrobin and tebuconazole, respectively. Mean EC50 of trifloxystrobin estimated by the conidial germination inhibition method was 0.002 &mu;g/ml. No mutations or EC50 values indicated shifts of fungicide sensitivity on the isolates.

Dans cette thèse, nous avons étudié la dynamique des parois de domaine sous courant dans des couches ferromagnétiques ultra-minces de type métal lourd/ métal ferromagnétique/ oxyde présentant un fort couplage spin-orbite. Dans ces systèmes, deux éléments liés au fort couplage spin-orbite et l'asymétrie structurelle d'inversion jouent un rôle clé sur la dynamique des parois : d'une part, l'amplitude des couples de spin-orbite (SOT) exercés sur la paroi lors de l'injection de courant; d'autre part, l'amplitude de l'interaction Dzyaloshinskii-Moriya qui stabilise la structure Néel interne de la paroi. L'objectif de ce travail a été de caractériser les couples agissant sur la paroi induits par le courant ainsi que l'amplitude de l'interaction DMI.Pour y parvenir, j'ai mis au point une nouvelle technique de mesure basée sur la mesure des déplacements nanométriques induits par le courant d'une paroi piégée dans un nanoplot découpé dans le matériau magnétique. Cette mesure quasi-statique permet de s'affranchir des difficultés liées à la modélisation de la dynamique des parois magnétique sous courant en présence de défauts.Par ailleurs, le dispositif a été conçu de façon à ce que le courant et le champ magnétique externe statique puissent être appliqués dans différentes directions orthogonales, ce qui permet séparer clairement les contributions des couples de transfert de spin (NA-STT) et de spin-orbite (DL-SOT).Les mesures ont permis de caractériser le couple exercé sur la paroi par le courant en fonction d'un champ magnétique planaire pour un empilement Pt/Co/AlOx et ceci pour quatre orientations champ/courant différentes. Les résultats permettent d'écarter l'hypothèse d'une structure de type Bloch bi-stable.Dans le cas où le courant est injecté au travers de la paroi, la comparaison des résultats avec le modèle aboutit à une valeur du couple NA-STT très faible. Nos mesures faites avec le champ magnétique planaire permettent de conclure à un champ SOT de 7,5+/-0,5 Oe pour 10 MA/m² en accord avec les résultats de couple publiés précédemment dans le cas d'une paroi de Néel. Si les deux configurations donnent de mesures de couple SOT similaire, elles ne permettent pas de conclure sur la valeur de DMI dans ce système. L'origine de ces valeurs contradictoires reste à expliquer. / In this thesis, we studied the current induced domain walls (DWs) dynamics in ultra-thin ferromagnetic films of heavy metal/ ferromagnetic metal/ oxide type with a high spin-orbit coupling. In these systems, two ingredients linked to the high spin-orbit coupling and the structural inversion asymmetry play a key role on the DWs dynamics: the amplitude of the spin-orbit torques (SOT) acting on the domain when a current is injected; and the amplitude of the Dzyaloshinskii-Moriya interaction (DMi) which stabilizes the Néel structure of the DW. The purpose of this work was to characterize the current induced torques acting on the DW and the amplitude of the DMi.For that purpose, I developed a new measurement technique relying on the measurement of current induced nanometer size motion of a DW, trapped inside a nanodot patterned in the magnetic material. This quasi-static measurement enables to avoid the difficulties related to the modelling of the DW dynamics in the presence of defects.Besides that, the device has been designed to enable different perpendicular directions for the current and the external magnetic field, which enable a clear measurement of spin transfer (NA-STT) and spin-orbit (DL-SOT) torques contributions.The measurements allowed the characterization of the torque exerted by the current on the DW with respect to a planar magnetic field for a Pt/Co/AlOx stack in 4 different couples of field/current directions. The results allow to exclude the hypothesis of a Bloch structure for the DW.In the case where the current is injected through the DW, the comparison between the results and the model leads to a very weak value for the NA-STT. Our measurements made with the planar magnetic field leads to a value of 7,5+/-0,5 Oe per 10 MA/m² for the DL-SOT, which is in agreement with previously published results in the case of a Néel DW. If both configurations lead to similar measurements for the SOT, they don't permit to conclude on the exact value of the DMi in this system. The origin of these contradictories values is still to be understood.

Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2018-02-15T15:43:47Z No. of bitstreams: 1 PGCA16MA185.pdf: 387046 bytes, checksum: c4b42029e4e9bd31fb6f0967fb2fe202 (MD5) / Made available in DSpace on 2018-02-15T15:43:47Z (GMT). No. of bitstreams: 1 PGCA16MA185.pdf: 387046 bytes, checksum: c4b42029e4e9bd31fb6f0967fb2fe202 (MD5) Previous issue date: 2016-02-22 / Capes / The inclusion of pasture in dairy feeding systems based on a total mixed ration (TMR) reduces feed costs, benefits herd health and reduces environmental impact. The present study aimed to evaluate the effect of ryegrass pasture (Lolium multiflorum Lam.) combined with a partial TMR or a TMR on the enteric methane emissions, dry matter intake (DMI), and performance of dairy cows from mid- to late lactation. The experimental treatments included 100% TMR (control), partial TMR + 6 h of continuous grazing (0900 – 1500 h) and partial TMR + 6 h of grazing that was divided into 2 periods of 3 h after milking (0900 – 1200 h; 1530 – 1830 h). Twelve F1 cows (Holstein × Jersey; 132 ± 44 days in milk) were divided into 6 lots and distributed in a 3 × 3 Latin square design with 3 periods of 21 d (15 d of adaptation and 6 d of evaluation). Ryegrass pasture was used, and the TMR was composed of 80% corn silage, 18% soybean meal, and 2% mineral and vitamins mixture, based on dry matter (DM). The same mixture was used for cows with access to pasture. The total DMI (average = 16.1 kg/d) and milk production ( average = 20.0 kg/d) were similar for all cows; however, the pasture DMI (7.4 vs. 6.0 kg/d) and grazing period (+ 40 min/d) were higher in cows that had access to pasture for 2 periods of 3 h compared to those that grazed for a continuous 6 h period. Methane emission was higher (656 vs. 547 g/d) in confined cows than in those receiving partial TMR + pasture. The inclusion of ryegrass pasture in the diet of dairy cows maintained animal performance and reduced enteric methane emissions. The percentage of grazed forage in the cow’s diet increased when access to pasture was provided in 2 periods after morning and afternoon milking / A inclusão da forragem em sistemas de produção de leite baseados em ração totalmente misturada (RTM) reduz os custos com a alimentação, traz benefícios à saúde do rebanho e reduz o impacto ambiental. O presente estudo objetivou avaliar o efeito do pastejo de azevém (Lolium multiflorum Lam.) combinado com o uso de RTM parcial em comparação à RTM sobre a emissão de metano, a ingestão de matéria seca (IMS) e o desempenho das vacas no terço médio de lactação. Os tratamentos experimentais foram 100% RTM (controle), RTM parcial + 6h de pastejo contínuo (09:00–15:00h) e RTM parcial + 6 h de pastejo divididos em dois períodos de três horas (09:00 – 12:00 h; 15:30 – 18:30h). Doze vacas F1 (Holandês × Jersey; 132 ± 44 DEL) foram divididas em seis lotes e distribuídas em um Quadrado latino com três períodos de 21 dias (15 dias de adaptação e 6 de dias avaliação). O pasto utilizado foi o azevém e a RTM foi composta de 80% de silagem de milho, 18% farelo de soja, e 2% de mistura mineral e vitaminas (na matéria seca, MS). A mesma mistura foi utilizada para as vacas com acesso ao pasto. A IMS total (média = 16,1 kg MS/dia) e a produção de leite (média = 20,0 kg leite/dia) foram similares entre os tratamentos, entretanto, a IMS de pasto (7,4 vs. 6,0 kg/d) e o tempo de pastejo (+ 40 min/d) foram superiores nas vacas com acesso ao pasto por dois períodos de 3h quando comparadas às vacas com acesso ao pasto por 6h contínuas. A emissão de metano foi maior (656 vs. 547 g/d) nas vacas confinadas do que nos animais recebendo RTM parcial + pasto. A inclusão de pasto de azevém na dieta de vacas leiteiras recebendo RTM manteve o desempenho animal e reduziu a emissão de metano entérico. A proporção de forragem pastejada aumentou nas vacas com acesso ao pasto quando o período de acesso foi dividido em dois períodos após a ordenha da manhã e a ordenha da tarde

This thesis explores the design and development of digitally extended, electro- acoustic (EA) pitched percussion instruments, and their use in novel, multi-media performance contexts. The proposed techniques address the lack of expressivity in existing EA pitched percussion systems. The research is interdisciplinary in na- ture, combining Computer Science and Music to form a type of musical human- computer interaction (HCI) in which novel playing techniques are integrated in perfor- mances. Supporting areas include Electrical Engineering- design of custom hardware circuits/DSP; and Mechanical Engineering- design/fabrication of new instruments. The contributions can be grouped into three major themes: 1) non-invasive gesture recognition using sensors and machine learning, 2) acoustically-excited physical mod- els, 3) timbre-recognition software used to trigger idiomatic acoustic actuation. In addition to pitched percussion, which is the main focus of the thesis, application of these ideas to other music contexts is also discussed. / Graduate

Sclerotinia homoeocarpa F.T. Bennett, the causal agent associated with dollar spot, is a common and economically challenging turfgrass disease in North America. Acceptable turfgrass quality requires the optimization of cultural practices and the judicious use of fungicides. Sclerotinia homoeocarpa causes significant damage to turfgrass swards from May to October annually, therefore, requiring multiple fungicide applications to maintain satisfactory turfgrass quality throughout the growing season. Sterol demethylation inhibitor (DMI) fungicides are among the most widely used in the United States and frequent use has led to the development of fungicide resistance to the DMI fungicide class. The precise mechanism of DMI fungicide resistance in S. homoeocarpa is not completely understood, however over expression of the CPY51A gene or efflux transporter genes have been reported as the molecular mechanism for other fungal systems. Fungicide resistance to the DMI class exhibits a gradual population shift towards insensitivity that can be monitored using In vitro fungicide sensitivity assays. In vitro fungicide sensitivity assays have been used to detect fungicide sensitivity differences in different S. homoeocarpa isolates and currently serve as the most accurate methodology to detect DMI insensitivity in S. homoeocarpa. Documentation of DMI field efficacy on native S. homoeocarpa populations with differing in vitro sensitivities has not been examined thoroughly and would provide critical information regarding the association between in vitro fungicide sensitivity and DMI field efficacy. The objectives of this research are (i) to determine the association between in vitro propiconazole sensitivity and reduced field efficacy for five native S. homoeocarpa populations and (ii) to develop a qualitative in vitro sensitivity assay for detection of S. homoeocarpa isolates responsible for practical field resistance.

Practical resistance of Erysiphe necator to quinone outside inhibitors (QoIs) is now widespread, and resistance to demethylation inhibitors (DMIs) has also developed.  The goal of this research was to characterize fungicide resistance by elucidating resistance mechanisms and determining its stability.  QoI resistance persisted for several years in a field population after QoI application ended.  Resistant isolates were highly competitive in mixed populations in competition assays under laboratory conditions, indicating a lack of fitness cost.  In one competition trial under field conditions, resistance frequency declined, possibly due to spore migration and influx of background inoculum, but in a second trial, it did not decline.  Double resistance to QoI and DMI was detected and DMI application may have been partially responsible for maintaining QoI resistance in the field.  One isolate with QoI resistance but an undetectable level of the major QoI mutation was shown to be heteroplasmic -- resistant strains could be selected from this isolate. DMI resistance mechanisms in E. necator included the Y136F mutation in CYP51 and cyp51 over-expression.  The first mechanism was present in almost all isolates with substantial levels of resistance, and cyp51 expression level was correlated with resistance level.  Three cyp51 genotypes were detected.  Wildtype isolates with the TAT genotype were sensitive to DMIs, while isolates with increased resistance had either a TTT or TWT genotype; TWT indicated the presence of both wildtype and mutant alleles.  Cyp51 was expressed 1.4 to 19 times more in mutants than in wildtype.  It is not known whether the significant differences in cyp51 expression level among isolates and among genotype groups are due to gene copy number variation.  DMI resistance was found to decline after years of subculturing, and the decline appeared to occur after a few culture transfers of field samples on fungicide-free host leaves.  The observed decline, together with the finding that isolates could be "trained" to increase resistance, and may be slightly induced in cyp51 expression when successively challenged to grow in increasing fungicide concentration, indicate instability of DMI resistance. / Ph. D.