Chlorosis of plants from a lack of available iron is one of the most common plant nutrient problems of the calcareous soils of the west. The disease is characterized by a yellowing of the plant leaves and is accompanied, in severe cases, by a partial root death and premature defoliation (3). In addition to reducing growth, the disease greatly reduces the quality and yield of plants. Many types of plants are affected by iron chlorosis. In Hawaii and Porto Rico rice, sugar cane and pineapple are susceptible, while in California and Arizona, citrus trees are seriously affected. In Utah apples, peaches, plums, prunes, apricots, pears, grapes, raspberries and many ornamental plants are affected (27). The problem of iron chlorosis, therefore, is of great importance to agriculture in the west. Chlorosis has been studied for more than one hundred and fifty years, but until recently, little progress has been made toward finding the solution to the problem. Although these past studies have not solved the problem of iron chlorosis, they have shown many factors to be closely related to the occurrence of the disease. These factors include an unbalanced ratio of available manganese to iron in the growth medium (9, 23, 29); chlorotic leaves are high in potassium, nitrogen in the form of ammonia (21), and in ferric iron and are low in total calcium and ferrous iron in comparison with green leaves (12, 13, 14, 17, 25, 26). The climatic factors of light, soil temperature and soil moisture also appear to be of fundamental importance in chlorosis. It is a common observation that fruit trees are more chlorotic during the early spring when the temperature of the soil is low and the moisture level high. Many investigators have noted that chlorosis tends to be most severe in the poorly drained portions of fruit orchards when water tends to accumulate. However, the work on the affect of climatic conditions on chlorosis has been limited largely to observations. The purpose of this investigation was to study, under controlled conditions, the effect of light, soil temperature and soil moisture on a lime-induced chlorosis.

Chlorosis, the yellowing of plant leaves, results from reduced synthesis of chlorophyll. It is caused by a deficiency or an unbalance of essential nutrient elements. The amount and pattern of yellowing varies with the cause and severity of the disturbance. Chlorosis results in reduced vigor of the affected plants and a corresponding loss in quantity and quality of the product grown. In severe cases chlorosis may lead to the eventual death of the plant. Lime-induced chlorosis refers to a chlorosis occurring on high lime soils. It affects principally horticultural plants. The disease is found in about 23 percent of Utah orchards. Lime-induced chlorosis is characteristically accompanied by high potasseium in the affected leaves. The hypothesis had been offered that this high potassium is a cause of lime-induced chlorosis. The object of this study is to investigate the validity of this hypothesis.

Iron deficiency chlorosis (IDC) is the most common reason for chlorosis in soybean (Glycine max (L.) Merrill) and causes an average yield loss of 120 million dollars per year across 1.8 million ha in the North Central US alone. As the most effective way to avoid IDC is the use of tolerant cultivars, they are visually rated for IDC by experts; however, this method is subjective and not feasible for a larger scale. An alternate more objective image processing method can be implemented in various platforms and fields. This approach relies on a color vegetation index (CVI) that can quantify chlorophyll, as chlorophyll content is a good IDC indicator. Therefore, this research is aimed at developing image processing methods at leaf, plot, and field scales with machine learning methods for chlorophyll and IDC measurement. This study also reviewed and synthesized the IDC measurement and management methods. Smartphone digital images with machine learning models successfully estimated the chlorophyll content of soybean leaves infield. Dark green color index (DGCI) was the best-correlated CVI with chlorophyll. The pixel count of four different ranges of DGCI (RPC) was used as input features for different models, and the support vector machine produced the highest performance. Handheld camera images of soybean plots extracted DGCI, which mimicked visual rating, and canopy size that were used as inputs to decision-tree based models for IDC classification. The AdaBoost model was the best model in classifying IDC severity. Unmanned aerial vehicle soybean IDC cultivar trial fields images extracted DGCI, canopy size, and their product (CDP) for IDC severity monitoring and yield prediction. The area under the curve (AUC) was employed to aggregate the data into a single value through time, and the correlation between all the features and yield was good. Although CDP at latest growth stage had the highest correlation with yield, AUC of CDP was the most consistent index for soybean yield prediction. This research demonstrated that digital image processing along with the machine learning methods can be successfully applied to the soybean IDC measurement and the various soybean related stakeholders can benefit from this research.

O Tomato chlorosis virus (ToCV), família Closteroviridae, gênero Crinivirus é um vírus de RNA de fita simples, senso positivo, transmitido de maneira semi-persistente por espécies da família Aleyrodidae, dos gêneros Bemisia e Trialeurodes. Possui uma gama de hospedeiros considerável que inclui plantas domesticadas e ervas daninhas das famílias Alzoaceae, Amaranthaceae, Apiaceae, Apocynaceae, Asteraceae, Plumbaginaceae, e Solanaceae. No estado de São Paulo, Brasil, foi relatado pela primeira vez em 2008, causando clorose internerval nas folhas de tomateiros. A importância desta doença emergente tem incrementado nos últimos anos e, no entanto, até o momento não existem estimativas dos danos causados nem alternativas adequadas para o manejo da doença no campo. Diante disso, esse trabalho teve como objetivos (i) avaliar a resistência de genótipos de tomateiro à infecção com o ToCV, (ii) avaliar a tolerância de alguns dos genótipos à doença e (iii) estimar o dano produzido em campo protegido. Para isso, 57 genótipos, incluindo espécies selvagens, linhagens avançadas e cultivares comerciais de tomateiro foram inicialmente avaliados quanto à resistência à infecção. Plantas jovens, produzidas em bandejas de poliestireno expandido, protegidas por gaiola recoberta com tecido de voil foram inoculadas por meio da liberação massal de B. tabaci MEAM1 virulífera para o ToCV. A incidência de plantas infectadas por genótipo foi determinada mediante observação dos sintomas e a detecção do vírus por RT-PCR. Alguns dos genótipos também foram avaliados quanto à tolerância à doença causada pelo crinivírus. Plantas sadias e sabidamente infectadas com o ToCV foram transplantadas no campo no interior de telados protegidos com tecido de voil. As plantas foram avaliadas quanto ao peso de frutos produzidos. No fim do ensaio, todas as plantas foram cortadas na região do colo e avaliaram-se os pesos fresco e seco da parte aérea. Em dois ensaios independentes de avaliação da resistência à infecção com o ToCV por meio da liberação massal de B. tabaci virulífera constatou-se que em condições de livre chance de escolha dos insetos os acessos Solanum peruvianum LA 444-1 e S. habrochaites PI 127826 e PI 134417 e as linhagens avançadas IAC 14-2-49+14-2-85 (somente no primeiro ensaio) e IAC 68F-22-2-24-1 não tiveram plantas infectadas, sugerindo alto grau de resistência à infecção pelo crinivírus. Para os demais genótipos avaliados a reação das plantas à infecção com o ToCV variou de moderadamente resistente à altamente suscetível. Dois ensaios independentes para avaliar a tolerância dos diferentes genótipos de tomateiro ao amarelão causado pelo ToCV, com base no desenvolvimento e na produção das plantas mostrou resultados bastante variáveis. Os resultados desse trabalho fornecerão subsídios para futuros trabalhos de melhoramento genético para o desenvolvimento de cultivares resistentes/tolerantes ao ToCV. / Tomato chlorosis virus (ToCV), family Closteroviridae, genus Crinivirus is a single-stranded, positive sense RNA virus, transmitted semi-persistently by species of the family Aleyrodidae, belonging to the genus Bemisia and Trialeurodes. ToCV infects several species including domesticated and weed plants belonging to the families Alzoaceae, Amaranthaceae, Apiaceae, Apocynaceae, Asteraceae, Plumbaginaceae and Solanaceae. In São Paulo, Brazil, this crinivirus was first reported in 2008, causing chlorosis in the leaves of tomato plants. The importance of this emerging disease has increased in recent years and yet, so far there are no estimates of the damage, nor suitable alternatives for the management of the disease in the field. Therefore, this study aimed to (i) evaluate the resistance of tomato genotypes to infection with ToCV, (ii) to evaluate the tolerance of some genotypes to the disease and (iii) estimate the damage produced in infected plants. Fifty seven genotypes, including wild species, hybrids and commercial tomato cultivars were initially evaluated for resistance to infection. Seedlings produced in expanded polystyrene trays protected by cage covered with voile fabric were inoculated through the mass release of ToCV viruliferous B. tabaci MEAM1. The incidence of infected plants per genotype was determined by observation of symptoms and virus detection by RT-PCR. Some of the genotypes were also evaluated for tolerance to the disease caused by the crinivirus. Healthy and ToCV infected plants were separately transplanted in the field, in cages protected with voile fabric. Weight of harvested fruits of the plants were evaluated. At the end of the test, all the plants were cut out and their fresh and dry weights were measured. Results from two independent trials showed that the accesses Solanum peruvianum LA 444-1, and S. habrochaites PI 127826 and PI 134417, and the hybrids IAC 14249+14285 and IAC 68F-22-2-24-1 did not have infected plants, suggesting a high degree of resistance to infection by the crinivirus. For all other genotypes the response of the plants to infection with ToCV ranged from moderately resistant to highly susceptible. Results from two independent trials to assess the tolerance of different tomato genotypes to the disease caused by ToCV, based on the development and production of the plants were widely variable. These findings provide insights for future breeding programs for the development of cultivars resistant and/or tolerant to ToCV.

A clorose variegada dos citros (CVC) é um dos principais problemas que assolam a citricultura brasileira nos últimos dez anos. Essa doença, causada pela bactéria Xylella fastidiosa, determina menor produção das plantas infectadas e tem estreita relação com as condições climáticas, sendo sua severidade agravada em regiões com baixa disponibilidade hídrica, alta demanda atmosférica e elevadas temperaturas. A fotossíntese, que possue relação direta com a produtividade das plantas, é um dos processos fisiológicos afetados pela CVC. Esse trabalho visou investigar os efeitos da temperatura na fotossíntese de plantas infectadas pela X. fastidiosa e determinar como o processo fotossintético é afetado pela presença da bactéria. Para tanto, foram utilizadas mudas de laranjeira 'Pêra' (Citrus sinensis (L.) Osbeck), com aproximadamente 9 meses de idade, cultivadas em vasos plásticos de 3L. Foram realizados dois experimentos. No experimento I, mudas sadias e doentes foram dispostas em câmara de crescimento e submetidas por 7 dias a regimes de temperatura de 25/20 e 35/20ºC (dia/noite), com concentrações de CO2 e O2 atmosféricas, 14h de fotoperíodo, densidade de fluxo de fótons fotossintéticos (DFFF) de 600umol m -2 s -1 e déficit de pressão de vapor do ar de 1kPa. Foram realizadas medidas simultâneas de trocas gasosas [assimilação de CO2 (A); transpiração (E) e condutância estomática (gs)] e fluorescência da clorofila a [eficiência quântica potencial (Fv/Fm) e efetiva ( F/Fm')do fotossistema II, taxa aparente de transporte de elétrons (ETR) e coeficientes de extinção fotoquímica (qP) e não-fotoquímica (NPQ) da fluorescência] em tecidos intactos, nas temperaturas de 25, 30, 35 e 40ºC. No experimento II, foram realizadas curvas de resposta da produção de oxigênio fotossintético (Ao) em função de DFFF e curvas de indução de Ao, com medidas simultâneas de Ao, DF/Fm', ETR, qP e NPQ, em discos foliares, nas temperaturas de 35 e 45ºC. No experimento I, as plantas com CVC apresentaram valores inferiores de A, E e gs, sendo que as diferenças entre plantas sadias e doentes foram maiores no regime de temperatura de 35/20ºC, onde foram registrados os maiores valores de A, E e gs. Essas variáveis tenderam a decrescer com o aumento da temperatura (de 25 para 40ºC), alcançando valores mínimos a 40ºC em ambos regimes de temperatura. No experimento I, a CVC não influenciou DF/Fm', ETR, qP e NPQ, porém, Fv/Fm das plantas com CVC foi superior em todas as medidas. As variáveis mais influenciadas pela temperatura foram DF/Fm', ETR e qP, as duas primeiras decrescendo e a última aumentando com o aumento da temperatura de medida. Os maiores valores de Fv/Fm , DF/Fm', ETR, qP e NPQ foram registrados no regime de 35/20ºC, confirmando que essas condições foram mais favoráveis à atividade fotossintética das plantas. No experimento II, as plantas sadias apresentaram os maiores valores de Ao, DF/Fm', ETR, qP e NPQ nas medidas efetuadas a 35ºC. A presença da bactéria afetou a indução de Ao em ambas temperaturas, porém as diferenças em DF/Fm', ETR, qP e NPQ foram encontradas apenas a 35ºC. Esses resultados indicaram que o aumento da temperatura afetou o sistema planta-patógeno agravando as disfunções no metabolismo fotossintético das plantas com CVC. A menor fotossíntese de laranjeira 'Pêra' infectada pela X. fastidiosa é atribuída a menor condutância estomática, comprometimento de reações bioquímicas e aumento da atividade fotorrespiratória. / The citrus variegated chlorosis (CVC) has became a great problem for the Brazilian citriculture during the last ten years. CVC, caused by the bacterium Xylella fastidiosa, causes a strong decrease in production of infected plants. Higher severities of the disease have been reported in areas with water deficit, high atmospheric demand and high temperatures. Photosynthesis, which has direct relationship with plant productivity, is a physiological process affected by CVC. The objectives of this study were to determine the effects of temperature upon photosynthesis of infected plants and to evaluate how the photosynthetic apparatus is affected by the presence of the bacterium. In order to achieve these objectives, two experiments (I and II) were carried out, using 9 months-old seedlings of sweet orange 'Pêra' (Citrus sinensis (L.) Osbeck), grown in 3L plastic pots under greenhouse conditions. In experiment I, prior to measurements, healthy and infected plants were moved to a plant growth chamber and exposed to temperature regimes of 25/20 and 35/20ºC (day/night) during 7 days each, CO2 and O2 atmospheric concentrations, 14h photoperiod, photosynthetically active radiation (PAR) of 600mmol m-2 s-1 and air vapor pressure difference of about 1 kPa. Simultaneous measurements of leaf gas exchange [CO2 assimilation (A); transpiration (E) and stomatal conductance (gs)] and chlorophyll fluorescence [potential (Fv/Fm) and effective (DF/Fm') quantum yield of photosystem II, apparent electron transport rate (ETR) and photochemical (qP) and non-photochemical (NPQ) fluorescence quenching] were taken in intact leaves, at 25, 30, 35 and 40ºC. In experiment II, light curves of photosynthetic oxygen evolution (Ao), and curves of photosynthesis induction were carried out, with simultaneous measurements of Ao, DF/Fm', ETR, qP and NPQ in leaf discs, at 35 and 45ºC. In experiment I, infected plants shown decrease in A, E and gs, and the differences between healthy and infected plants were greater at 35/20ºC, where the largest values of A, E and gs were observed. These variables decreased with increasing temperature, reaching minimum values at 40ºC for both temperature regimes. In experiment I, no differences between healthy and infected plants regarding chlorophyll fluorescence variables were observed. However, Fv/Fm of infected plants was higher in all conditions. The three most influenced variables by temperature were DF/Fm', ETR and qP, whereas the two first decreased while the last increased with increasing temperature. Largest values of Fv/Fm, DF/Fm', ETR, qP and NPQ were registered at 35/20ºC, confirming that this temperature regime was more adequate to plant photosynthetic activity. In experiment II, healthy plants showed the largest values of Ao, DF/Fm', ETR, qP and NPQ at 35ºC. The presence of the bacterium affected Ao induction in both temperatures, however, differences in DF/Fm', ETR, qP and NPQ for healthy and infected plants were only found at 35ºC. Results from this study indicated that increase in temperature affected the plant-pathogen system, amplifying the malfunction of the photosynthetic metabolism of infected plants. The smallest photosynthetic rates of sweet orange 'Pêra' infected by X. fastidiosa were caused by low stomatal conductance, biochemical injuries and photorespiratory activity.

Lime-induced chlorosis has been recognized for many years as a problem where plants are grown on calcareous soils. There are many factors associated with and influencing this form of iron chlorosis and because of this it has been very difficult to determine the relationship between the factors and chlorosis. There are high concentrations of bicarbonate in calcareous soils. Because of this high concentration, it was believed that the presence of the bicarbonate ion was causing chlorosis. It has been proposed that the pH of the growth medium was the causitive factor of lime-induced chlorosis. Most calcareous soils have a pH range around 8.0. At this pH the solubility of iron is very low, and it was believed that chlorosis was a result of iron being insoluble at a high pH. Iron chlorosis has been induced in plants by increasing the phosphorus concentration in the growth medium. Iron phosphates have a low solubility and it was believed that the available iron was precipitated by the phosphates. The interference of metals such as calcium, nickel, cobalt, zinc, and copper appears to be a factor affecting the absorption of iron by plants. It was thought that an interfering ion (Ni, Co, Ca, Zn) may interfere with the translocation of iron in the malic or malonic acid complexes (Tiffin and Brown, 1962).

Made available in DSpace on 2014-06-11T19:28:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-05-20Bitstream added on 2014-06-13T19:37:12Z : No. of bitstreams: 1 franco_f_me_jabo.pdf: 3490988 bytes, checksum: e452cf8f45511970030cfe537c850cae (MD5) / Funep / Seis cultivares de laranjeiras doces (Sanguínea, Olivelands, Vaccaro Blood, Folha Murcha, São Miguel e Finike) foram avaliadas no campo em quatro experimentos e cada experimento sobre um porta-enxerto (limoeiro ‘Cravo’, citrumeleiro ‘Swingle’, tangerineiras ‘Sunki’ e ‘Cleópatra’). Durante a safra 2005/2006, foram avaliadas quanto às características que convencionalmente são atribuídas à qualidade dos frutos (massa, altura, diâmetro, rendimento de suco, teor de sólidos solúveis, acidez titulável e ratio). Na safra 2006/2007, foram quantificados os danos provocados pela Clorose Variegada dos Citros e, em ambas, quanto à produção de frutos e de sólidos solúveis por árvore. Na ocasião da colheita de cada cultivar, seus frutos mostraram-se semelhantes quanto às características químicas. As cultivares Olivelands e Finike destacaram-se em relação à produção de frutos, porém a ‘Olivelands’ se destacou também pela maior produção de sólidos solúveis por planta. Quanto a reação à CVC, houve diferenças entre as cultivares quanto à intensidade de doença e na produção de frutos de plantas sadias em comparação com as doentes, nos dois anos de avaliação. ‘Olivelands’ e ‘Finike’ apresentaram baixos índices de doença e pequena diferença na produção de frutos e sólidos entre suas plantas sadias e doentes, mostrando maior tolerância à infecção por Xilella fastidiosa. / Six sweet orange cultivars (Sanguínea, Olivelands, Vaccaro Blood, Folha Murcha, San Miguel and Finike) were evaluated in four experiments. Each budded on a rootstock (Rangpur lime, ‘Cleopatra’ and ‘Sunki’ mandarins and ‘Swingle’ citrumelo). Over 2005/2006 season, the characteristics that are conventionally attributed to the fruits quality (weight, height, diameter, yield of juice, soluble solids, acidity and ratio) were evaluated. In the 2006/2007, the damage caused by Citrus Variegated Chlorosis, and in both, as the fruit and soluble solids yield per tree were quantified. At the each cultivar harvest, its fruits have shown similar chemical characteristics. 'Olivelands' and 'Finike' highlighted up to the fruit yield, but the 'Olivelands' stood out also by the increased production of soluble solids per tree. In reaction to Xilella fastidiosa infection, there were differences to the cultivars on the disease intensity and the fruit yield by healthy trees compared with patients in two years of evaluation. 'Olivelands' and 'Finike' showed low rates of disease and small difference in the fruit and soluble solids yield to their plants healthy and sick, showing greater tolerance to Xilella fastidiosa infection.

A clorose variegada dos citros (CVC) é um dos principais problemas que assolam a citricultura brasileira nos últimos dez anos. Essa doença, causada pela bactéria Xylella fastidiosa, determina menor produção das plantas infectadas e tem estreita relação com as condições climáticas, sendo sua severidade agravada em regiões com baixa disponibilidade hídrica, alta demanda atmosférica e elevadas temperaturas. A fotossíntese, que possue relação direta com a produtividade das plantas, é um dos processos fisiológicos afetados pela CVC. Esse trabalho visou investigar os efeitos da temperatura na fotossíntese de plantas infectadas pela X. fastidiosa e determinar como o processo fotossintético é afetado pela presença da bactéria. Para tanto, foram utilizadas mudas de laranjeira 'Pêra' (Citrus sinensis (L.) Osbeck), com aproximadamente 9 meses de idade, cultivadas em vasos plásticos de 3L. Foram realizados dois experimentos. No experimento I, mudas sadias e doentes foram dispostas em câmara de crescimento e submetidas por 7 dias a regimes de temperatura de 25/20 e 35/20ºC (dia/noite), com concentrações de CO2 e O2 atmosféricas, 14h de fotoperíodo, densidade de fluxo de fótons fotossintéticos (DFFF) de 600umol m -2 s -1 e déficit de pressão de vapor do ar de 1kPa. Foram realizadas medidas simultâneas de trocas gasosas [assimilação de CO2 (A); transpiração (E) e condutância estomática (gs)] e fluorescência da clorofila a [eficiência quântica potencial (Fv/Fm) e efetiva ( F/Fm')do fotossistema II, taxa aparente de transporte de elétrons (ETR) e coeficientes de extinção fotoquímica (qP) e não-fotoquímica (NPQ) da fluorescência] em tecidos intactos, nas temperaturas de 25, 30, 35 e 40ºC. No experimento II, foram realizadas curvas de resposta da produção de oxigênio fotossintético (Ao) em função de DFFF e curvas de indução de Ao, com medidas simultâneas de Ao, DF/Fm', ETR, qP e NPQ, em discos foliares, nas temperaturas de 35 e 45ºC. No experimento I, as plantas com CVC apresentaram valores inferiores de A, E e gs, sendo que as diferenças entre plantas sadias e doentes foram maiores no regime de temperatura de 35/20ºC, onde foram registrados os maiores valores de A, E e gs. Essas variáveis tenderam a decrescer com o aumento da temperatura (de 25 para 40ºC), alcançando valores mínimos a 40ºC em ambos regimes de temperatura. No experimento I, a CVC não influenciou DF/Fm', ETR, qP e NPQ, porém, Fv/Fm das plantas com CVC foi superior em todas as medidas. As variáveis mais influenciadas pela temperatura foram DF/Fm', ETR e qP, as duas primeiras decrescendo e a última aumentando com o aumento da temperatura de medida. Os maiores valores de Fv/Fm , DF/Fm', ETR, qP e NPQ foram registrados no regime de 35/20ºC, confirmando que essas condições foram mais favoráveis à atividade fotossintética das plantas. No experimento II, as plantas sadias apresentaram os maiores valores de Ao, DF/Fm', ETR, qP e NPQ nas medidas efetuadas a 35ºC. A presença da bactéria afetou a indução de Ao em ambas temperaturas, porém as diferenças em DF/Fm', ETR, qP e NPQ foram encontradas apenas a 35ºC. Esses resultados indicaram que o aumento da temperatura afetou o sistema planta-patógeno agravando as disfunções no metabolismo fotossintético das plantas com CVC. A menor fotossíntese de laranjeira 'Pêra' infectada pela X. fastidiosa é atribuída a menor condutância estomática, comprometimento de reações bioquímicas e aumento da atividade fotorrespiratória. / The citrus variegated chlorosis (CVC) has became a great problem for the Brazilian citriculture during the last ten years. CVC, caused by the bacterium Xylella fastidiosa, causes a strong decrease in production of infected plants. Higher severities of the disease have been reported in areas with water deficit, high atmospheric demand and high temperatures. Photosynthesis, which has direct relationship with plant productivity, is a physiological process affected by CVC. The objectives of this study were to determine the effects of temperature upon photosynthesis of infected plants and to evaluate how the photosynthetic apparatus is affected by the presence of the bacterium. In order to achieve these objectives, two experiments (I and II) were carried out, using 9 months-old seedlings of sweet orange 'Pêra' (Citrus sinensis (L.) Osbeck), grown in 3L plastic pots under greenhouse conditions. In experiment I, prior to measurements, healthy and infected plants were moved to a plant growth chamber and exposed to temperature regimes of 25/20 and 35/20ºC (day/night) during 7 days each, CO2 and O2 atmospheric concentrations, 14h photoperiod, photosynthetically active radiation (PAR) of 600mmol m-2 s-1 and air vapor pressure difference of about 1 kPa. Simultaneous measurements of leaf gas exchange [CO2 assimilation (A); transpiration (E) and stomatal conductance (gs)] and chlorophyll fluorescence [potential (Fv/Fm) and effective (DF/Fm') quantum yield of photosystem II, apparent electron transport rate (ETR) and photochemical (qP) and non-photochemical (NPQ) fluorescence quenching] were taken in intact leaves, at 25, 30, 35 and 40ºC. In experiment II, light curves of photosynthetic oxygen evolution (Ao), and curves of photosynthesis induction were carried out, with simultaneous measurements of Ao, DF/Fm', ETR, qP and NPQ in leaf discs, at 35 and 45ºC. In experiment I, infected plants shown decrease in A, E and gs, and the differences between healthy and infected plants were greater at 35/20ºC, where the largest values of A, E and gs were observed. These variables decreased with increasing temperature, reaching minimum values at 40ºC for both temperature regimes. In experiment I, no differences between healthy and infected plants regarding chlorophyll fluorescence variables were observed. However, Fv/Fm of infected plants was higher in all conditions. The three most influenced variables by temperature were DF/Fm', ETR and qP, whereas the two first decreased while the last increased with increasing temperature. Largest values of Fv/Fm, DF/Fm', ETR, qP and NPQ were registered at 35/20ºC, confirming that this temperature regime was more adequate to plant photosynthetic activity. In experiment II, healthy plants showed the largest values of Ao, DF/Fm', ETR, qP and NPQ at 35ºC. The presence of the bacterium affected Ao induction in both temperatures, however, differences in DF/Fm', ETR, qP and NPQ for healthy and infected plants were only found at 35ºC. Results from this study indicated that increase in temperature affected the plant-pathogen system, amplifying the malfunction of the photosynthetic metabolism of infected plants. The smallest photosynthetic rates of sweet orange 'Pêra' infected by X. fastidiosa were caused by low stomatal conductance, biochemical injuries and photorespiratory activity.

O Tomato chlorosis virus (ToCV), família Closteroviridae, gênero Crinivirus é um vírus de RNA de fita simples, senso positivo, transmitido de maneira semi-persistente por espécies da família Aleyrodidae, dos gêneros Bemisia e Trialeurodes. Possui uma gama de hospedeiros considerável que inclui plantas domesticadas e ervas daninhas das famílias Alzoaceae, Amaranthaceae, Apiaceae, Apocynaceae, Asteraceae, Plumbaginaceae, e Solanaceae. No estado de São Paulo, Brasil, foi relatado pela primeira vez em 2008, causando clorose internerval nas folhas de tomateiros. A importância desta doença emergente tem incrementado nos últimos anos e, no entanto, até o momento não existem estimativas dos danos causados nem alternativas adequadas para o manejo da doença no campo. Diante disso, esse trabalho teve como objetivos (i) avaliar a resistência de genótipos de tomateiro à infecção com o ToCV, (ii) avaliar a tolerância de alguns dos genótipos à doença e (iii) estimar o dano produzido em campo protegido. Para isso, 57 genótipos, incluindo espécies selvagens, linhagens avançadas e cultivares comerciais de tomateiro foram inicialmente avaliados quanto à resistência à infecção. Plantas jovens, produzidas em bandejas de poliestireno expandido, protegidas por gaiola recoberta com tecido de voil foram inoculadas por meio da liberação massal de B. tabaci MEAM1 virulífera para o ToCV. A incidência de plantas infectadas por genótipo foi determinada mediante observação dos sintomas e a detecção do vírus por RT-PCR. Alguns dos genótipos também foram avaliados quanto à tolerância à doença causada pelo crinivírus. Plantas sadias e sabidamente infectadas com o ToCV foram transplantadas no campo no interior de telados protegidos com tecido de voil. As plantas foram avaliadas quanto ao peso de frutos produzidos. No fim do ensaio, todas as plantas foram cortadas na região do colo e avaliaram-se os pesos fresco e seco da parte aérea. Em dois ensaios independentes de avaliação da resistência à infecção com o ToCV por meio da liberação massal de B. tabaci virulífera constatou-se que em condições de livre chance de escolha dos insetos os acessos Solanum peruvianum LA 444-1 e S. habrochaites PI 127826 e PI 134417 e as linhagens avançadas IAC 14-2-49+14-2-85 (somente no primeiro ensaio) e IAC 68F-22-2-24-1 não tiveram plantas infectadas, sugerindo alto grau de resistência à infecção pelo crinivírus. Para os demais genótipos avaliados a reação das plantas à infecção com o ToCV variou de moderadamente resistente à altamente suscetível. Dois ensaios independentes para avaliar a tolerância dos diferentes genótipos de tomateiro ao amarelão causado pelo ToCV, com base no desenvolvimento e na produção das plantas mostrou resultados bastante variáveis. Os resultados desse trabalho fornecerão subsídios para futuros trabalhos de melhoramento genético para o desenvolvimento de cultivares resistentes/tolerantes ao ToCV. / Tomato chlorosis virus (ToCV), family Closteroviridae, genus Crinivirus is a single-stranded, positive sense RNA virus, transmitted semi-persistently by species of the family Aleyrodidae, belonging to the genus Bemisia and Trialeurodes. ToCV infects several species including domesticated and weed plants belonging to the families Alzoaceae, Amaranthaceae, Apiaceae, Apocynaceae, Asteraceae, Plumbaginaceae and Solanaceae. In São Paulo, Brazil, this crinivirus was first reported in 2008, causing chlorosis in the leaves of tomato plants. The importance of this emerging disease has increased in recent years and yet, so far there are no estimates of the damage, nor suitable alternatives for the management of the disease in the field. Therefore, this study aimed to (i) evaluate the resistance of tomato genotypes to infection with ToCV, (ii) to evaluate the tolerance of some genotypes to the disease and (iii) estimate the damage produced in infected plants. Fifty seven genotypes, including wild species, hybrids and commercial tomato cultivars were initially evaluated for resistance to infection. Seedlings produced in expanded polystyrene trays protected by cage covered with voile fabric were inoculated through the mass release of ToCV viruliferous B. tabaci MEAM1. The incidence of infected plants per genotype was determined by observation of symptoms and virus detection by RT-PCR. Some of the genotypes were also evaluated for tolerance to the disease caused by the crinivirus. Healthy and ToCV infected plants were separately transplanted in the field, in cages protected with voile fabric. Weight of harvested fruits of the plants were evaluated. At the end of the test, all the plants were cut out and their fresh and dry weights were measured. Results from two independent trials showed that the accesses Solanum peruvianum LA 444-1, and S. habrochaites PI 127826 and PI 134417, and the hybrids IAC 14249+14285 and IAC 68F-22-2-24-1 did not have infected plants, suggesting a high degree of resistance to infection by the crinivirus. For all other genotypes the response of the plants to infection with ToCV ranged from moderately resistant to highly susceptible. Results from two independent trials to assess the tolerance of different tomato genotypes to the disease caused by ToCV, based on the development and production of the plants were widely variable. These findings provide insights for future breeding programs for the development of cultivars resistant and/or tolerant to ToCV.

Iron deficiency chlorosis (IDC) is a frequent problem in soybean [Glycine max (L.) Merr.] production on calcareous soils. Greenhouse and soil incubation experiments were established to evaluate pyritic lignite efficacy to supply Fe as compared to Fe-EDDHA and Fe-EDTA sources across contrasting IDC tolerance varieties grown on a slightly acid and a calcareous soil. Soybean IDC incidence was influenced by the soil properties and variety tolerance. All iron sources increased plant dry matter accumulation on the Leeper soil, whereas on the Marietta soil only lignite at 0.672 kg ha-1 produced an increase. Lignite at 0.336 kg ha-1 successfully improved Fe availability to the plant as reflected by an increase in Fe content. Furthermore, no differences were found between the low rate of lignite and the commercial fertilizers on any of the evaluated parameters. Results from this study indicate that pyritic lignite may serve as an acceptable source of Fe on problem soils to prevent IDC.