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Search Results: 1 - 10 of 9555 matches for " Prabhu Anne Sitarama "
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Eficiência relativa de fontes de silício no controle de brusone nas folhas em arroz
Berni, Rodrigo Fascin;Prabhu, Anne Sitarama;
Pesquisa Agropecuária Brasileira , 2003, DOI: 10.1590/S0100-204X2003000200005
Abstract: silicon fertilization of rice is one of the alternatives for reducing the use of fungicides in the control of rice blast. an experiment was conducted, during 1999/2000 and repeated in 2000/2001, in order to study the efficiency of sources of silicon (si) to reduce leaf blast on rice cultivar metica-1, cultivated in the low land. the treatments included three sources of si (high furnace silicate slag, serpentinite ore rich in silicon and wollastonite ore, a native calcium metasilicate) at five doses (0, 0.5, 1.0, 2.0 and 4.0 mg ha-1), with and without fungicide treatment (pyroquilon 200 g a.i. per 100 kg of seed). the blast disease severity decreased with increase in si doses. the relationship between area under disease progress curve and doses of silicate slag as well as wollastonite were linear and negative, with and without seed treatment. furthermore, the results show the increased efficiency of seed fungicide treatment in reducing blast severity, with silicon fertilization.
Controle de brusone e manejo de nitrogênio em cultivo de arroz irrigado
Fageria, Nand Kumar;Prabhu, Anne Sitarama;
Pesquisa Agropecuária Brasileira , 2004, DOI: 10.1590/S0100-204X2004000200004
Abstract: nitrogen timing and control of fungal diseases are cultural practices in lowland rice production. the objective of this study was to determine appropriate timing of n application and adequate rate of seed treatment with pyroquilon fungicide in lowland rice. the 90 kg ha-1 n application timing were alloted as follows: total at sowing (t1); 1/3 at sowing, 1/3 at active tillering and 1/3 at panicle initiation (t2); 1/2 at sowing and 1/2 at active tillering (t3); 1/2 at sowing and 1/2 at panicle initiation (t4); 2/3 at sowing and 1/3 at active tillering (t5); 2/3 at sowing and 1/3 at panicle initiation (t6); and 1/3 at sowing and 2/3 at the start of tillering (t7). fungicide treatments were 0, 200, and 400 g active ingredient pyroquilon per 100 kg seed. grain yield was significantly affected with timing of n application and fungicide treatments. nitrogen treatment also affected significantly straw yield, and n uptake in grain. maximum grain yield was obtained with treatments t2 and t3. fungicide treatment of 200 g per100 kg of seed, produced significantly higher yield as compared to the control.
Graus de resistência à brusone e produtividade de cultivares melhoradas de arroz de terras altas
Prabhu, Anne Sitarama;Filippi, Marta Cristina;
Pesquisa Agropecuária Brasileira , 2001, DOI: 10.1590/S0100-204X2001001200002
Abstract: the aim of this work was to study the levels of leaf and panicle blast resistance and their effect on grain yield of 12 rice cultivars, in a field experiment, during consecutive three years. the degree of leaf blast and panicle blast resistance was determined by the assessment criteria of area under disease progress curve and disease severity ten days before the harvest, respectively. the cultivars progresso, cuiabana, caiapó, carajás and araguaia were superior in descending order for leaf blast resistance. for panicle blast, carajás and progresso, exhibited lower disease severities than the rest of the cultivars in the first two years. the grain yields during three years ranged from 83 kg/ha for iac 201 to 3,617 kg/ha for rio paraguai, and the variation was explained by blast severity, in the panicles, as the correlations were negative. the races ib-9, ib-41, ib-13 and ic-27 of pyricularia grisea obtained from 13 cultivars showed differential interaction. these results permitted to conclude that the degree of resistance of some of the cultivars was inadequate and other measures of disease control are necessary.
Phenotypic virulence analysis of Pyricularia grisea isolates from Brazilian upland rice cultivars
Filippi, Marta Cristina;Prabhu, Anne Sitarama;
Pesquisa Agropecuária Brasileira , 2001, DOI: 10.1590/S0100-204X2001000100004
Abstract: phenotypic virulence analysis was made on population of pyricularia grisea isolates collected from 10 upland cultivars in three distinct rice breeding sites, with the objective of studying the degree of similarity in the phenotypic virulence among the isolates, the composition of races, and their virulence pattern. sixteen races were identified based on the reaction type on eight standard international differentials, the predominant ones being ib9 and ib41. the virulence frequency was high on iac47 and iac165 among medium and early maturing cultivars, respectively. the frequency of isolates virulent was greater on upland rice cultivars (51.1%) than on irrigated rice cultivars (21.8%). both virulent and avirulent isolates were present in the population of p. grisea to the known genes in the near isogenic lines. of72test isolates, 94.4% were virulent for genes pi3 and pi4a. thevirulence frequencies were relatively lower in decreasing order on pi1, pi4b and pi2. thecoefficient of similarity ranged from 0.28 to1.0 among the isolates pertaining to different races, while within the race ib9, it varied from 0.56 to1.0. considering the coefficient of similarity of 0.81, 72% of isolates of race ib9 exhibited similar pattern of virulence.
Controle de brusone e manejo de nitrogênio em cultivo de arroz irrigado
Fageria Nand Kumar,Prabhu Anne Sitarama
Pesquisa Agropecuária Brasileira , 2004,
Abstract: Informa es sobre práticas culturais, tais como a aplica o de N e o controle de doen as causadas por fungos, em solo de várzea do Brasil s o insuficientes. O objetivo deste trabalho foi avaliar a resposta do arroz irrigado a épocas de aplica o de N e ao tratamento das sementes com fungicida no controle de brusone. Aplicaram-se 90 kg ha-1 de N da seguinte forma: todo no plantio (T1); 1/3 no plantio, 1/3 45 dias após o plantio e 1/3 na inicia o do primórdio floral (T2); 1/2 no plantio e 1/2 45 dias após o plantio (T3); 1/2 no plantio e 1/2 na inicia o do primórdio floral (T4); 2/3 no plantio e 1/3 45 dias após o plantio (T5); 2/3 no plantio e 1/3 aplicado na inicia o do primórdio floral (T6) e 1/3 no plantio e 2/3 20 dias após o plantio (T7). O fungicida pyroquilon foi aplicado nas doses de 0, 200 e 400 g de ingrediente ativo por 100 kg de sementes. A produ o de gr os foi influenciada significativamente pela época de aplica o de N e pelo tratamento de fungicida. A aplica o de N influenciou significativamente a matéria seca da parte aérea e a acumula o de N nos gr os. A produ o máxima de gr os foi obtida pelos tratamentos T2 e T3. O tratamento com 200 g de fungicida por 100 kg de sementes aumentou significativamente a produ o de gr os, em rela o à testemunha.
Eficiência relativa de fontes de silício no controle de brusone nas folhas em arroz
Berni Rodrigo Fascin,Prabhu Anne Sitarama
Pesquisa Agropecuária Brasileira , 2003,
Abstract: A aduba o silicatada constitui uma das alternativas para diminuir o uso de fungicidas no controle da brusone em arroz. Foi realizado um experimento, durante 1999/2000 e repetido durante 2000/2001, com o objetivo de estudar a eficiência relativa de fontes de silício (Si) na redu o da severidade da brusone nas folhas da cultivar Metica-1, em área de várzea. Os tratamentos foram três fontes de Si (silicato de alto forno; serpentinito, minério rico em Si e wollastonita, um metasilicato de cálcio natural), em cinco doses (0, 0,5, 1,0, 2,0 e 4,0 Mg ha-1) sem tratamento das sementes ou com tratamento das sementes com o fungicida pyroquilon 200 g de i.a. por 100 kg. A severidade da brusone diminuiu significativamente com o aumento de doses de silício. As rela es entre a área sob curva de progresso da doen a e as doses, tanto do silicato de alto forno quanto da wollastonita, foram lineares e negativas, com ou sem tratamento de sementes, em ambos os anos do experimento. Os resultados revelam o aumento da eficiência do tratamento das sementes com fungicida na redu o da brusone nas folhas com a fertiliza o silicatada.
Phenotypic virulence analysis of Pyricularia grisea isolates from Brazilian upland rice cultivars
Filippi Marta Cristina,Prabhu Anne Sitarama
Pesquisa Agropecuária Brasileira , 2001,
Abstract: Phenotypic virulence analysis was made on population of Pyricularia grisea isolates collected from 10 upland cultivars in three distinct rice breeding sites, with the objective of studying the degree of similarity in the phenotypic virulence among the isolates, the composition of races, and their virulence pattern. Sixteen races were identified based on the reaction type on eight standard international differentials, the predominant ones being IB9 and IB41. The virulence frequency was high on IAC47 and IAC165 among medium and early maturing cultivars, respectively. The frequency of isolates virulent was greater on upland rice cultivars (51.1%) than on irrigated rice cultivars (21.8%). Both virulent and avirulent isolates were present in the population of P. grisea to the known genes in the near isogenic lines. Of72test isolates, 94.4% were virulent for genes Pi3 and Pi4a. Thevirulence frequencies were relatively lower in decreasing order on Pi1, Pi4b and Pi2. Thecoefficient of similarity ranged from 0.28 to1.0 among the isolates pertaining to different races, while within the race IB9, it varied from 0.56 to1.0. Considering the coefficient of similarity of 0.81, 72% of isolates of race IB9 exhibited similar pattern of virulence.
Graus de resistência à brusone e produtividade de cultivares melhoradas de arroz de terras altas
Prabhu Anne Sitarama,Filippi Marta Cristina
Pesquisa Agropecuária Brasileira , 2001,
Abstract: O objetivo deste trabalho foi estudar o nível de resistência à brusone nas folhas e panículas e seu efeito sobre a produtividade de 12 cultivares de arroz, em experimento de campo, durante três anos consecutivos. O grau de resistência das cultivares à brusone nas folhas e panículas foi determinado utilizando-se o critério de área sob curva de progresso e severidade de brusone nas panículas dez dias antes de colheita, respectivamente. As cultivares Progresso, Cuiabana, Caiapó, Carajás e Araguaia, em ordem decrescente, foram as mais resistentes à brusone nas folhas. As cultivares Carajás e Progresso apresentaram severidades da brusone, nas panículas, menores do que as demais cultivares em dois anos. A produtividade das cultivares nos três anos de avalia es, que variou de 83 kg/ha na IAC 201 a 3.617 kg/ha na Rio Paraguai, é explicada principalmente pela severidade da brusone nas panículas, já que as correla es foram negativas e significativas. As ra as de Pyricularia grisea, IB-9, IB-41, IB-13 e IC-27, provenientes de 13 cultivares, apresentaram intera es diferenciais. Os resultados permitiram concluir que o grau de resistência de algumas cultivares é inadequado e necessita de outras medidas de controle.
Comportamento de somaclones de arroz derivados de híbridos da gera??o F1 para resistência à brusone
Araújo, Leila Garcês de;Prabhu, Anne Sitarama;
Pesquisa Agropecuária Brasileira , 2002, DOI: 10.1590/S0100-204X2002000500006
Abstract: the induction of genetic variability, in relation to blast resistance, using tissue culture as a tool, constitutes one of the alternatives for obtaining novel resistance gene sources. the objective of this study was to increase the frequency of variants using immature panicles as explant from the f1 plants of crosses involving susceptible and moderately blast resistant sources as parents. somaclones of rice derived from f1 plants of the crosses bluebelle/araguaia and maratelli/basmati-370 were assessed in advanced generations for blast resistance and some agronomic characters. in the greenhouse inoculation tests, all somaclones of both crosses in r4 generation exhibited a high degree of blast resistance to pathotypes ib-1 and ib-9. some of them remained resistant in the r5 generation under a high disease pressure. in the field evaluation of r5 and r6 generations somaclones showed a high frequency of variation for blast resistance, plant height, grain weight, grain type and yield. two somaclones derived from the crosses bluebelle/araguaia and 31 somaclones developed from the cross between cultivars maratelli/basmati-370 were identified as novel blast resistant sources which can be utilized in the irrigated rice breeding program.
Somaclones da cultivar de arroz aromático Basmati-370 resistentes à brusone
Araújo, Leila Garcês de;Prabhu, Anne Sitarama;
Pesquisa Agropecuária Brasileira , 2002, DOI: 10.1590/S0100-204X2002000800010
Abstract: basmati-370 is one of the most preferred aromatic fine quality rice in the world market. it has a pleasant aroma, extra fine grain and a characteristic elongation after cooking, but it is susceptible to some pathotypes of pyricularia grisea in brazil. the objective of the present investigation was to assess the degree of blast resistance and some agronomic characteristics in the advanced generations of its somaclones. the evaluations were carried out in r5 to r9 generations, in field trials, in rice blast nursery and greenhouse. significant variations in grain quality and other agronomic characteristics were not observed. however, some of the somaclones showed higher degree of blast resistance. nineteen somaclones were registered in the active germplasm bank of embrapa-centro nacional de pesquisa de arroz e feij?o as new aromatic rice sources. two somaclones, scbas04 and sbas16, exhibited a high degree of partial resistance to blast, and were found to be superior to cv. basmati-370 in aromatic grain characteristic.
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