<I>Bean pod mottle virus </I>(BPMV, Genus <I>Comovirus</I>, Family: <I>Comoviridae</I>)is an important virus in soybean (<I>Glycine max</I> (L.) Merrill), causing quality and yield loss due to seed coat mottling and seed weight reduction. Although BPMV has been known in Virginia since 1958 and has always been regarded as causing negligible losses, its impact is changing as BPMV incidence has increased in many soybean growing areas of Virginia and the USA in general. From 1997 to 2001, a total of five BPMV isolates (V-W1, V-W2, V-S98-1, V-S98-15 and V-S01-10) were collected in Virginia and characterized. In this study, the effects of these isolates were studied, alone or with Soybean mosaic virus (SMV, Genus Potyvirus, Family Potyviridae) strain SMV G1, and isolates S98-51 and S98-52, on selected soybean cultivars. Individual isolates of BPMV showed variable symptom severity, and resulted in yield loss of between 40.4 to 58.1%, while SMV caused 23.7% in the most severe interactions. Up to 100% yield loss was realized from double inoculations of selected BPMV and SMV isolates, BPMV V-S98-1 + SMV S98-52 and BPMV S98-15 + SMV S98-52 on Hutcheson and Hutcheson Roundup Ready&#174; (BC5) soybeans, respectively. Time of inoculation, a critical factor in the impact of many virus diseases, affected seed coat mottling in four cultivars and seed weight in two cultivars, in tests with four BPMV isolates and three stages of soybean development. All BPMV isolates inoculated to plants at vegetative stage V1-V3 severely increased seed coat mottling and reduced seed weight than those inoculated at V4-V6 and reproductive stage R1-R3. Seedlings grown from non-mottled seeds germinated more uniformly had fewer thin-stemmed seedlings and grew faster than those grown from mottled seeds. Inoculation of various cultivars and breeding lines showed that there was no correlation between the severity of virus-induced foliar symptoms, relative accumulation of SMV, and extent of seed coat mottling. Thus, by avoiding the presence of BPMV at an early growth stage through proper timing of planting to avoid vectors, proper cultural practices like weed control, use of SMV free seeds, and chemical control, it is possible to greatly improve seed quality and reduce yield losses in soybean. / Ph. D.

No description available.

Master of Science / Entomology / Brian McCornack / Several lepidopteran species infest developing panicles. Larval identification is challenging and time intensive, so current recommendations are often simplified by treating all larvae equally across species. Consequently, the yield-loss model developed for corn earworm (Helicoverpa zea) by Buckley and Burkhardt (1962) has been the foundation for management recommendations in modern sorghum Integrated Pest Management (IPM) programs for the last 49 years. Additionally, although pest populations primarily include both fall armyworm (Spodoptera frugiperda) and corn earworm, only a single species damage estimate is used in economic threshold (ET) and economic injury level (EIL) calculations despite multi-species infestations. This research demonstrates both the validation of current management recommendations for corn earworm and the verification of previously assumed damage potentials for fall armyworm feeding in developing sorghum panicles. These results have important implications for sorghum producers faced with making a management decision for multi-species infestations.

O Zucchini lethal chlorosis virus (ZLCV) é uma espécie do gênero Tospovirus, transmitido por tripes, que infecta diversas espécies da família Cucurbitaceae. Já foi constatado em diversos estados brasileiros e sua incidência tem aumentado significativamente nos últimos anos em algumas regiões. Por se tratar de uma virose em potencial para as cucurbitáceas, pouco se conhece sobre os danos causados e a reação das diferentes espécies de cucurbitáceas à infecção em campo. Esse trabalho teve por objetivos: estudar a eficiência da RT-PCR para a detecção rápida e especifica do ZLCV em cucurbitáceas; avaliar os danos causados pelo ZLCV em abobrinha de moita em campo e a reação de sete espécies/variedades de cucurbitáceas à infecção natural A detecção do ZLCV por RT-PCR foi estudada utilizando um par de oligonucleotídeos iniciadores, desenhados com base na seqüência do S-RNA do ZLCV (AF067069). Quatro espécies de tospovírus (TSWV, TCSV, GRSV e CSNV) e outros vírus que infectam cucurbitáceas (PRSV-W-1, PRSV-W-C, ZYMV-M, ZYMV-Atibaia e CMV) foram incluídos no teste. Na reação de RT-PCR foi obtido um fragmento de aproximadamente 350 pb, amplificado somente a partir de RNA total extraído de planta infectada com o ZLCV. A seqüência obtida desse fragmento apresentou 98,2 % de identidade com a seqüência de nucleotídeos do S-RNA do ZLCV depositada no GenBank. Os danos causados pelo ZLCV em abobrinha de moita &#39;Caserta&#39; foram avaliados em campo na ESALQ/USP, Piracicaba-SP, onde esse vírus é freqüente. As plantas foram monitoradas semanalmente quanto à infecção pelo ZLCV por meio dos sintomas e por PTA-ELISA. As plantas foram agrupadas em função da época de aparecimento dos sintomas do ZLCV, avaliando a produção de frutos comerciais (FC) e não comerciais (FNC) de cada grupo e comparando com a de plantas que permaneceram sem sintomas até o final do experimento. As plantas que apresentaram sintomas até os 23 dias após a emergência (DAE) não produziram qualquer tipo de frutos. FC foram colhidos de plantas que apresentaram sintomas a partir dos 42 DAE. Mesmo assim, houve redução de 78,5 % na produção de FC. Plantas que mostraram sintomas por ocasião da última colheita (55 DAE) apresentaram redução na produção de FC de 9,6 %. A infecção com o ZLCV até o início da frutificação inviabiliza a produção de FC de abobrinha de moita &#39;Caserta&#39;. A reação de sete espécies/variedades de cucurbitáceas à infecção com o ZLCV foi avaliada em campo, por meio da infecção natural e em casa de vegetação, onde as plantas foram duplamente inoculadas mecanicamente com o ZLCV no estádio cotiledonar. A avaliação foi feita com base no monitoramento dos sintomas e por PTA-ELISA. A abobrinha de moita &#39;Caserta&#39; e a abóbora híbrida &#39;Takaiama&#39; apresentaram alta suscetibilidade ao ZLCV. O pepino &#39;Safira&#39; apresentou baixa infecção em campo e intermediária em casa de vegetação. Enquanto que a melancia &#39;Crimson Sweet&#39;, o maxixe do Norte, a abóbora rasteira &#39;Menina Brasileira&#39; e a moranga &#39;Alice&#39; apresentaram valores menores de infecção. A moranga &#39;Exposição&#39; foi altamente resistente, pois não foi infectada nos ensaios em campo e em casa de vegetação. / Zucchini lethal chlorosis virus is a specie of the Genus Tospovirus, transmitted by thrips (Frankliniella zucchini), which infects some species of the family Cucurbitaceae. The occurrence of this Tospovirus has already been reported for several Brazilian states and its incidence in cucurbit crops has increased in the last years in some regions. Considering the importance of this Tospovirus for cucurbit crops, very little is known about the damage caused by this virus and the reaction of the different species of cucurbits to infection. This work aimed: to study the efficiency of the RT-PCR for the fast and specific detection of ZLCV, to evaluate the damage caused by this virus on zucchini squash under field condition and the reaction of seven species/varieties of cucurbits to infection with this Tospovirus. The detection of ZLCV by RT-PCR was studied using a pair of primers designed based on the nucleotide sequence of the SRNA of ZLCV (AF067069). Four other Tospovirus species (TSWV, TCSV, GRSV and CSNV) and other virus that infect cucurbits (mild strain PRSV-W-1, wild strain PRSV-WC, mild strain ZYMV-M, wild strain ZYMV-Atibaia and CMV) were included in this test. The RT-PCR reaction generated a fragment of approximately 350 bp, only amplified from total RNA extracted from plant infected with ZLCV. The sequence of this fragment presented 98.2 % identity with the corresponding nucleotide sequence of the S-RNA of ZLCV deposited in the GenBank. The damage caused by ZLCV on zucchini squash (Cucurbita pepo cv. Caserta) was evaluated under field condition. Zucchini squash plants were weekly monitored for the presence of characteristic symptoms induced by ZLCV and PTA-ELISA for virus indexing. Plants were grouped based on the time the symptoms were first seen. Fruits harvested from each plant within each group were classified on marketable (M) and non-marketable (NM) based on the phenotype. Plants that did not show symptoms by the end of the crop were considered still healthy and their yield was used as control. Zucchini squash plants that showed symptoms of ZLCV infection up to 23 days after emergency (DAE) did not yield any fruit. Marketable fruits were first harvested only from plants that showed symptoms 42 DAE. However, the yield of marketable fruits was reduced by 78.5 %, as compared to that from asymptomatic plants. Plants that showed symptoms 55 DAE showed a reduction on the yield of marketable fruit of 9.6%. The reaction of seven species/varieties of cucurbits to infection with ZLCV was evaluated under field and greenhouse conditions. In the field experiment, ZLCV infection occurred naturally. In the greenhouse, plants were twice mechanically inoculated with ZLCV at the cotyledonal stage. Evaluations were based on symptoms expression and PTA-ELISA. Zucchini squash &#39;Caserta&#39; and hybrid squash &#39;Takaiama&#39; were highly susceptible. The cucumber &#39;Safira&#39; presented low percentage of infected plants in the field and intermediate in the greenhouse. Watermelon &#39;Crimson Sweet&#39;, northern gherkin, long neck squash &#39;Menina Brasileira&#39; and winter squash &#39;Alice&#39; presented lower values of infected plants. Winter squash &#39;Exposição&#39; was highly resistant to infection under field and greenhouse conditions.

O presente trabalho tem como objetivo analisar os modelos matemáticos existentes na literatura para descrever as perdas de rendimento ocasionadas por plantas daninhas considerando o seu ajuste matemático e a sua interpretação biológica bem como ajustar um modelo às perdas obtidas para a cultivar de milho BRS1030, cultivada em área com pivô central em sistema de plantio direto, localizada na área experimental da EMBRAPA Milho e Sorgo situada no município de Sete Lagoas, Minas Gerais. Os modelos adotados são lineares, hiperbólicos e sigmóides com variáveis independentes sendo a densidade e a biomassa de plantas daninhas. A escolha de modelos para os dados utilizados é feita com base na análise estatística de resíduos e na significância dos parâmetros. Em adição, diferentes análises de indicativos de perda de rendimento e associações entre densidade e biomassa, cobertura foliar e produção de sementes, densidade e produção de sementes e, biomassa e produção de sementes foram realizadas. Resultados obtidos com o aplicativo estatístico R para a cultivar de milho infestada por dezoito espécies daninhas são apresentados. / The goal of this work is to present a review on the existing mathematical models used to describe the yield loss considering both their mathematical fit and their biological meaning as well as to adjust a model to the yield loss obtained with a corn cultivar BRS1030 grown in an experimental farm of the Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), located in Sete Lagoas, Minas Gerais, Brazil. The considered models are the linear, hyperbolic and sigmoid models with weed density and biomass as the independent variables. The choice of the model for the obtained data is accomplished by the statistical analysis of the errors and significance of the parameters. In addiction, analysis of the indicatives of yield loss and associations between weed density and biomass, weed coverage and weed seeds production, density and production of weed seeds and, biomass and production of weed seeds are performed. Results of a corn cultivar infested by eighteen weed species obtained with the statistical software R are presented.

O presente trabalho tem como objetivo analisar os modelos matemáticos existentes na literatura para descrever as perdas de rendimento ocasionadas por plantas daninhas considerando o seu ajuste matemático e a sua interpretação biológica bem como ajustar um modelo às perdas obtidas para a cultivar de milho BRS1030, cultivada em área com pivô central em sistema de plantio direto, localizada na área experimental da EMBRAPA Milho e Sorgo situada no município de Sete Lagoas, Minas Gerais. Os modelos adotados são lineares, hiperbólicos e sigmóides com variáveis independentes sendo a densidade e a biomassa de plantas daninhas. A escolha de modelos para os dados utilizados é feita com base na análise estatística de resíduos e na significância dos parâmetros. Em adição, diferentes análises de indicativos de perda de rendimento e associações entre densidade e biomassa, cobertura foliar e produção de sementes, densidade e produção de sementes e, biomassa e produção de sementes foram realizadas. Resultados obtidos com o aplicativo estatístico R para a cultivar de milho infestada por dezoito espécies daninhas são apresentados. / The goal of this work is to present a review on the existing mathematical models used to describe the yield loss considering both their mathematical fit and their biological meaning as well as to adjust a model to the yield loss obtained with a corn cultivar BRS1030 grown in an experimental farm of the Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), located in Sete Lagoas, Minas Gerais, Brazil. The considered models are the linear, hyperbolic and sigmoid models with weed density and biomass as the independent variables. The choice of the model for the obtained data is accomplished by the statistical analysis of the errors and significance of the parameters. In addiction, analysis of the indicatives of yield loss and associations between weed density and biomass, weed coverage and weed seeds production, density and production of weed seeds and, biomass and production of weed seeds are performed. Results of a corn cultivar infested by eighteen weed species obtained with the statistical software R are presented.

O Zucchini lethal chlorosis virus (ZLCV) é uma espécie do gênero Tospovirus, transmitido por tripes, que infecta diversas espécies da família Cucurbitaceae. Já foi constatado em diversos estados brasileiros e sua incidência tem aumentado significativamente nos últimos anos em algumas regiões. Por se tratar de uma virose em potencial para as cucurbitáceas, pouco se conhece sobre os danos causados e a reação das diferentes espécies de cucurbitáceas à infecção em campo. Esse trabalho teve por objetivos: estudar a eficiência da RT-PCR para a detecção rápida e especifica do ZLCV em cucurbitáceas; avaliar os danos causados pelo ZLCV em abobrinha de moita em campo e a reação de sete espécies/variedades de cucurbitáceas à infecção natural A detecção do ZLCV por RT-PCR foi estudada utilizando um par de oligonucleotídeos iniciadores, desenhados com base na seqüência do S-RNA do ZLCV (AF067069). Quatro espécies de tospovírus (TSWV, TCSV, GRSV e CSNV) e outros vírus que infectam cucurbitáceas (PRSV-W-1, PRSV-W-C, ZYMV-M, ZYMV-Atibaia e CMV) foram incluídos no teste. Na reação de RT-PCR foi obtido um fragmento de aproximadamente 350 pb, amplificado somente a partir de RNA total extraído de planta infectada com o ZLCV. A seqüência obtida desse fragmento apresentou 98,2 % de identidade com a seqüência de nucleotídeos do S-RNA do ZLCV depositada no GenBank. Os danos causados pelo ZLCV em abobrinha de moita &#39;Caserta&#39; foram avaliados em campo na ESALQ/USP, Piracicaba-SP, onde esse vírus é freqüente. As plantas foram monitoradas semanalmente quanto à infecção pelo ZLCV por meio dos sintomas e por PTA-ELISA. As plantas foram agrupadas em função da época de aparecimento dos sintomas do ZLCV, avaliando a produção de frutos comerciais (FC) e não comerciais (FNC) de cada grupo e comparando com a de plantas que permaneceram sem sintomas até o final do experimento. As plantas que apresentaram sintomas até os 23 dias após a emergência (DAE) não produziram qualquer tipo de frutos. FC foram colhidos de plantas que apresentaram sintomas a partir dos 42 DAE. Mesmo assim, houve redução de 78,5 % na produção de FC. Plantas que mostraram sintomas por ocasião da última colheita (55 DAE) apresentaram redução na produção de FC de 9,6 %. A infecção com o ZLCV até o início da frutificação inviabiliza a produção de FC de abobrinha de moita &#39;Caserta&#39;. A reação de sete espécies/variedades de cucurbitáceas à infecção com o ZLCV foi avaliada em campo, por meio da infecção natural e em casa de vegetação, onde as plantas foram duplamente inoculadas mecanicamente com o ZLCV no estádio cotiledonar. A avaliação foi feita com base no monitoramento dos sintomas e por PTA-ELISA. A abobrinha de moita &#39;Caserta&#39; e a abóbora híbrida &#39;Takaiama&#39; apresentaram alta suscetibilidade ao ZLCV. O pepino &#39;Safira&#39; apresentou baixa infecção em campo e intermediária em casa de vegetação. Enquanto que a melancia &#39;Crimson Sweet&#39;, o maxixe do Norte, a abóbora rasteira &#39;Menina Brasileira&#39; e a moranga &#39;Alice&#39; apresentaram valores menores de infecção. A moranga &#39;Exposição&#39; foi altamente resistente, pois não foi infectada nos ensaios em campo e em casa de vegetação. / Zucchini lethal chlorosis virus is a specie of the Genus Tospovirus, transmitted by thrips (Frankliniella zucchini), which infects some species of the family Cucurbitaceae. The occurrence of this Tospovirus has already been reported for several Brazilian states and its incidence in cucurbit crops has increased in the last years in some regions. Considering the importance of this Tospovirus for cucurbit crops, very little is known about the damage caused by this virus and the reaction of the different species of cucurbits to infection. This work aimed: to study the efficiency of the RT-PCR for the fast and specific detection of ZLCV, to evaluate the damage caused by this virus on zucchini squash under field condition and the reaction of seven species/varieties of cucurbits to infection with this Tospovirus. The detection of ZLCV by RT-PCR was studied using a pair of primers designed based on the nucleotide sequence of the SRNA of ZLCV (AF067069). Four other Tospovirus species (TSWV, TCSV, GRSV and CSNV) and other virus that infect cucurbits (mild strain PRSV-W-1, wild strain PRSV-WC, mild strain ZYMV-M, wild strain ZYMV-Atibaia and CMV) were included in this test. The RT-PCR reaction generated a fragment of approximately 350 bp, only amplified from total RNA extracted from plant infected with ZLCV. The sequence of this fragment presented 98.2 % identity with the corresponding nucleotide sequence of the S-RNA of ZLCV deposited in the GenBank. The damage caused by ZLCV on zucchini squash (Cucurbita pepo cv. Caserta) was evaluated under field condition. Zucchini squash plants were weekly monitored for the presence of characteristic symptoms induced by ZLCV and PTA-ELISA for virus indexing. Plants were grouped based on the time the symptoms were first seen. Fruits harvested from each plant within each group were classified on marketable (M) and non-marketable (NM) based on the phenotype. Plants that did not show symptoms by the end of the crop were considered still healthy and their yield was used as control. Zucchini squash plants that showed symptoms of ZLCV infection up to 23 days after emergency (DAE) did not yield any fruit. Marketable fruits were first harvested only from plants that showed symptoms 42 DAE. However, the yield of marketable fruits was reduced by 78.5 %, as compared to that from asymptomatic plants. Plants that showed symptoms 55 DAE showed a reduction on the yield of marketable fruit of 9.6%. The reaction of seven species/varieties of cucurbits to infection with ZLCV was evaluated under field and greenhouse conditions. In the field experiment, ZLCV infection occurred naturally. In the greenhouse, plants were twice mechanically inoculated with ZLCV at the cotyledonal stage. Evaluations were based on symptoms expression and PTA-ELISA. Zucchini squash &#39;Caserta&#39; and hybrid squash &#39;Takaiama&#39; were highly susceptible. The cucumber &#39;Safira&#39; presented low percentage of infected plants in the field and intermediate in the greenhouse. Watermelon &#39;Crimson Sweet&#39;, northern gherkin, long neck squash &#39;Menina Brasileira&#39; and winter squash &#39;Alice&#39; presented lower values of infected plants. Winter squash &#39;Exposição&#39; was highly resistant to infection under field and greenhouse conditions.

No description available.

No description available.

Proportional loss models commonly used in disease surveys are based on the assumption that per cent yield loss is the same in all crops, regardless of their yield potential. Estimates of regional crop loss may be inaccurate if the relationship between disease and yield loss is affected by crop yield potential. The importance of crop yield potential in disease: yield loss modelling was investigated and models for more accurate regional crop loss estimates were developed, taking crop yield potential into account. Two spring sown barley (cv. Triumph) experiments were conducted in 1987/88 and 1988/89 in Canterbury, New Zealand, to study the effect of crop yield potential on the relationship between disease and yield loss. Crop yield potentials of 323 to 806gDM/m² were generated in seven crops by varying nitrogen and water inputs, sowing date (mid-spring and early-summer) and season. Leaf rust (Puccinia hordei Otth) epidemics of different severity were generated by applying fungicides at different times, frequencies and rates to control the natural epidemics. Disease was measured as per cent disease severity (%DS), green leaf area, radiation interception and near-infrared radiation (NIR) reflectance from crop canopies. Yield was measured as total and grain dry weight. Epidemics were severe in the fully diseased plots from GS 34 and 46 to maturity in the late and early sown crops respectively. Disease reduced grain yield by 50 to 63% in 1987/88 and 24 to 38% in 1988/89 in the fully diseased plots. Disease: yield loss models were derived by regression analysis for each crop in 1987/88. Single point, multiple point and area under curve models were derived from %DS and GLAI variables, and proportional (%) and actual (gDM/m²) grain yield. The effect of yield potential was determined by comparing regression equation coefficients for each crop with crop yield potential. An area under green leaf area index curve (AUGLAIC): actual yield model was best suited to determining the effect of yield potential on yield loss. This model was selected because AUGLAIC summarised the effect of disease on plant growth over the season and actual yield represented the crop yield potential in the absence of disease and the response of actual yield to disease. Crop yield potential did not affect actual yield loss caused by leaf rust. Disease measured as AUGLAIC explained most of the variation in yield (R²adj=0.93) for all crops in both years. Assessment of GLAI is not suitable for estimation of regional crop loss because of the requirement for a rapid and low cost method. Reflectance of NIR from the crop canopy was investigated as an alternative to GLAI measurements. Reflectance was correlated significantly (P<0.001) with GLAI (r=0.66 to 0.89) and green area index (r=0.76 to 0.92). Reflectance measured at grain-filling (GS 85-87) explained most (R²adj=0.94) of the variation in yield for all crops in both years. The relationship between AUGLAIC and yield was validated with data from independent diseased and healthy barley crops. The AUGLAIC: yield model described the effects of disease on yield accurately but overestimated yield by 49 to 108% in the healthy crops. Models based on accumulated PAR (photosynthetically active radiation) intercepted by green leaves explained the observed deviations in yield of these crops from the AUGLAIC: yield model. Accumulated PAR models accounted for differences in incident radiation, canopy structure, radiation interception by green leaves, radiation use efficiency and harvest index which are important in determining dry matter production and grain yield. Accumulated PAR models described the effects of disease on crop growth which were not represented by GLAI alone. Variation in crop yield potential at the regional scale is important in disease: yield loss modelling and can be accounted for by using either separate equations for each yield potential crop or crop category, robust models, inclusion of a form function for yield potential or choice of disease and yield variables which integrate yield potential.