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Search Results: 1 - 10 of 9187 matches for " Anne Sitarama;Filippi "
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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.
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.
Cultivar response to fungicide application in relation to rice blast control, productivity and sustainability
Prabhu, Anne Sitarama;Filippi, Marta Cristina;Zimmermann, Francisco José Pfeilsticker;
Pesquisa Agropecuária Brasileira , 2003, DOI: 10.1590/S0100-204X2003000100002
Abstract: four field trials were conducted, from 1995 to 1997, with the objective of studying the response of four upland cultivars to foliar fungicide application in relation to panicle blast control, grain yield and sustainability. differential disease control and yield response of cultivars to fungicide treatment were obtained. losses in grain yield of cultivars iac 202, caiapó, rio paranaíba and araguaia due to panicle blast were 44.8%, 27.4%, 24.4% and 18.2%, respectively. two applications of tricyclazole or benomyl controlled panicle blast, as indicated by lower values of disease progress curve and relative panicle blast severity, and increased grain yield of the cultivar iac 202. the losses in 100 panicle grain weight and grain yield were significantly reduced by 22.3% and 25.1% in iac 202 and 23.6% and 20.5% in caiapó, respectively, with two sprays of tricyclazole. sustainable value index for yield was maximum with two applications of tricyclazole (0.59), followed by one application at booting (0.46) and at heading (0.40) in cultivar iac 202. results showed no yield response of the cultivars rio paranaíba and araguaia to fungicide applications for panicle blast control.
Cultivar response to fungicide application in relation to rice blast control, productivity and sustainability
Prabhu Anne Sitarama,Filippi Marta Cristina,Zimmermann Francisco José Pfeilsticker
Pesquisa Agropecuária Brasileira , 2003,
Abstract: Four field trials were conducted, from 1995 to 1997, with the objective of studying the response of four upland cultivars to foliar fungicide application in relation to panicle blast control, grain yield and sustainability. Differential disease control and yield response of cultivars to fungicide treatment were obtained. Losses in grain yield of cultivars IAC 202, Caiapó, Rio Paranaíba and Araguaia due to panicle blast were 44.8%, 27.4%, 24.4% and 18.2%, respectively. Two applications of tricyclazole or benomyl controlled panicle blast, as indicated by lower values of disease progress curve and relative panicle blast severity, and increased grain yield of the cultivar IAC 202. The losses in 100 panicle grain weight and grain yield were significantly reduced by 22.3% and 25.1% in IAC 202 and 23.6% and 20.5% in Caiapó, respectively, with two sprays of tricyclazole. Sustainable value index for yield was maximum with two applications of tricyclazole (0.59), followed by one application at booting (0.46) and at heading (0.40) in cultivar IAC 202. Results showed no yield response of the cultivars Rio Paranaíba and Araguaia to fungicide applications for panicle blast control.
Resistência de cultivares de arroz a Rhizoctonia solani e Rhizoctonia oryzae
Prabhu, Anne Sitarama;Filippi, Marta Cristina;Silva, Gisele Barata da;Santos, Gil Rodrigo de;
Pesquisa Agropecuária Brasileira , 2002, DOI: 10.1590/S0100-204X2002000500003
Abstract: isolates of rhizoctonia solani and rhizoctonia oryzae, the causal agents of sheath blight and sheath rot diseases, respectively, were collected from irrigated rice fields in the state of tocantins, brazil. the main objective of the investigation was to assess the resistance of 12 genotypes to these diseases, under artificial inoculation tests in greenhouse condition. there was no correlation between the resistance of cultivars to r. oryzae and r. solani for lesion extension on sheath infection obtained by the toothpick method. the relationship between lesion size on sheath and leaf was linear and significantly negative (r = -0.66, p£0.05), thereby indicating that there is no relationship between resistance of sheath and leaf to infection by r. solani in rice cultivars. among the early maturing genotypes labelle was highly susceptible in all methods of inoculation. the area under disease progress curve based on lesion height on the culm and the inoculation method with rice husk and grain were found more adequate for determining the differences in the degree of resistance among cultivars. leaves exhibited resistance to infection by r. oryzae in inoculation tests with mycelial discs.
Relationship between potassium fertilization and panicle blast severity in upland rice
Prabhu, Anne Sitarama;Barbosa Filho, Morel Pereira;Filippi, Marta Cristina;Zimmermann, Francisco José Pfeilsticker;
Pesquisa Agropecuária Brasileira , 1999, DOI: 10.1590/S0100-204X1999000900025
Abstract: the influence of k2o (0, 40, 80, 120 kg ha-1) at varying rates of n application (0, 30, 60 kg ha-1) at planting, on panicle blast (pyricularia grisea (cooke) sacc.) was studied in a field experiment conducted during three consecutive years with the upland rice cultivar dourad?o. panicle blast severity decreased with increasing rates of potassium in the absence of nitrogen (n0). the relationship between panicle blast and k rates was quadratic at 30 kg ha-1 of nitrogen. significant response to k fertilization was not obtained at 60 kg ha-1 of nitrogen in relation to panicle blast severity.
Genetic diversity and virulence pattern in field populations of Pyricularia grisea from rice cultivar Metica-1
Filippi, Marta Cristina;Prabhu, Anne Sitarama;Araújo, Leila Garcês de;Faria, Josias Correa de;
Pesquisa Agropecuária Brasileira , 2002, DOI: 10.1590/S0100-204X2002001200002
Abstract: rice blast is a major yield constraint of the irrigated rice in the state of tocantins, brazil. the objective of this investigation was to study the phenotypic and genetic diversity within the pathogen population of pyricularia grisea in samples collected from four individual farms of rice cultivar metica-1, under epidemic conditions of leaf blast. a set of 87 isolates was tested on 32 rice genotypes including eight international differentials. considering 80% similarity in virulence, two groups comprising a total of 81 isolates were recognized, independently of the farms from which they were collected. eighty percent of the isolates pertained to pathotype id-14, indicating high cultivar specificity and narrow diversity of virulence in the sample population. the virulence in pathogen population on rice cultivars br-irga 409 and rio formoso was low. analysis of p. grisea isolates using rep-pcr with two primer sequences from pot2 generated fingerprint profiles of one to nine bands. cluster analysis revealed the occurrence of six fingerprint groups with similarities ranging from 0.09 to 1. there was no straight relationship between virulence of the isolates based on reaction pattern on 32 genotypes and grouping based on pot2 rep-pcr analysis of p. grisea isolates collected from 'metica-1'.
Variantes somaclonais da cultivar de arroz Bluebelle resistentes à brusone
Araújo, Leila Garcês de;Prabhu, Anne Sitarama;Filippi, Marta Cristina;Oliveira, Wilson Ferreira de;
Pesquisa Agropecuária Brasileira , 2001, DOI: 10.1590/S0100-204X2001000500010
Abstract: rice blast, caused by pyricularia grisea, is the major yield constraint in irrigated rice mainly in the state of tocantins. the detection of genetic variability for blast resistance in susceptible cultivars such as bluebelle, considered as a standard for superior grain quality, was the main objective of the present investigation. the adopted procedure included the induction of callus from the immature panicles, regeneration, evaluation and selection of r2 plants for blast resistance. the same procedure was repeated using three selected r2 plants. the disease assessment and selection of blast resistant plants were done in r2 and r4 generations in blast nursery. in greenhouse tests with three isolates obtained from the cultivar metica1 belonging to pathotypes ib41 and ib45 of p. grisea, all of the 47 somaclones r6 were resistant. they showed differential reaction to five isolates of somaclones and were resistant to one isolate derived from cultivar bluebelle, while cultivar bluebelle was susceptible to all isolates. these results indicated genetic variation for blast resistance in second step of induction and regeneration of plants. of these 47 somaclones r6, 22 showed a high degree of vertical resistance in blast nursery tests conducted at four locations and can be utilized as new blast resistant sources.
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