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Indu o de variabilidade na cultivar de arroz Metica-1 para resistência a Pyricularia grisea  [cached]
Araújo Leila Garcês de,Prabhu Anne Sitarama
Pesquisa Agropecuária Brasileira , 2002,
Abstract: A brusone é um dos fatores limitantes da produtividade da cultivar Metica-1, no Estado do Tocantins. Objetivando obter somaclones resistentes, foi realizada a indu o de calos e a regenera o de plantas a partir de panículas imaturas da cultivar Metica-1. Duzentas e oitenta plantas R2 foram submetidas a inocula o inóculo de patótipos de Pyricularia grisea, ID-14 e II-1, provenientes das cultivares Metica-1 e Cica-8, respectivamente. Enquanto todas as 280 plantas R2 de Metica-1 foram resistentes em rela o ao patótipo II-1, as progênies de duas plantas R1 mostraram resistência ao patótipo ID14, indicando a indu o de varia o genética com rela o à resistência à brusone na cultivar suscetível, nas gera es iniciais. A gera o R3 foi avan ada e entre 280 somaclones R4 foram selecionados 51, incluindo dois somaclones, CNAI10390 e CNAI10393, que mostraram resistência vertical no viveiro de brusone. Nas gera es avan adas de R5 e R6, estes dois somaclones apresentaram resistência no viveiro e nas inocula es com cinco isolados, provenientes das cultivares Metica-1, Cica-8 e Epagri 108, e poder o ser usados como novas fontes de resistência à brusone nos programas de melhoramento de arroz.
Indu??o de variabilidade na cultivar de arroz Metica-1 para resistência a Pyricularia grisea
Araújo, Leila Garcês de;Prabhu, Anne Sitarama;
Pesquisa Agropecuária Brasileira , 2002, DOI: 10.1590/S0100-204X2002001200003
Abstract: rice blast is one of the yield limiting factors of the rice cultivar metica-1, in the state of tocantins, brazil. plants of this cultivar were regenerated from the callus cultures derived from immature panicles with the objective of obtaining blast resistant somaclones. two hundred eighty r2 plants were assessed utilizing pathotypes id-14 and ii-1 of pyricularia grisea, retrieved from the cultivars metica-1 and cica-8, respectively. while all r2 plants of the cultivar metica1 were resistant to the pathotype ii-1, the progenies of two r1 plants showed resistance to pathotype id-14, indicating thereby the induction of genetic variation for blast resistance in the susceptible rice cultivar, in early generations. the r3 generation was advanced, and of 280 somaclones in r4 generation, 51 were selected including two somaclones cnai10390 and cnai10393, which exhibited vertical resistance, in blast nursery. in the advanced r5 and r6 generations, these two somaclones showed resistant reaction in blast nursery test, as well as in inoculation tests with the isolates from the cultivars metica-1, cica-8 and epagri 108, and can be used as new blast resistant sources in rice breeding programs.
Virulence and rep-PCR analysis of Pyricularia grisea isolates from two Brazilian upland rice cultivars
Prabhu, Anne S.;Araújo, Leila G.;Silva, Gisele B.;Trindade, Maria G.;
Fitopatologia Brasileira , 2007, DOI: 10.1590/S0100-41582007000100002
Abstract: the phenotypic and genetic diversity of 77 isolates of pyricularia grisea collected from two upland rice cultivars, maravilha and primavera, was studied. isolates exhibiting compatible reaction to cv.primavera were incompatible to cv.maravilha and vice versa, with the exception of six isolates that were compatible to both cultivars. the virulence of isolates from cv. maravilha on 32 test genotypes of rice was significantly higher (t = 9.09, p < 0.0001) than the isolates from cv.primavera. a phenogram constructed from virulence data showed two main groups, one constituted mainly of isolates from cv.primavera (97.6%) and the other of isolates from cv.maravilha (91.17%). rep-pcr analysis of isolates using two primers designed from sequences of pot2 showed that isolates could be clustered broadly into two groups. the average similarity within a cluster of isolates from cv.primavera was significantly greater than the average similarity among the isolates of cv.maravilha (t = 5.37, p < 0.0001). there was close correspondence between clusters based on pcr and virulence data (r = 0.48, p < 0.011). the results showed that isolates of p. grisea were cultivar specific and had low phenotypic and genetic diversity.
Virulence pattern of Pyricularia grisea isolates from farmers' fields on newly released upland rice cultivars
Araújo, Leila G.;Prabhu, Anne S.;Silva, Gisele B. da;
Fitopatologia Brasileira , 2005, DOI: 10.1590/S0100-41582005000600009
Abstract: the virulence pattern of the isolates of pyricularia grisea from commercial fields of the upland rice (oryza sativa) cultivars 'primavera' and 'brs bonan?a' was analyzed. a hundred and seventy monoconidial isolates of the pathogen virulent to 'primavera' and 139 to 'brs bonan?a' collected from eight fields, during two years (2001-2003) were tested, under greenhouse conditions, on six newly released rice cultivars. differences in virulence pattern were observed in pathogenic populations of 'primavera' and 'brs bonan?a'. isolates with virulence to improved cultivars were common in samples from farmers' fields in the absence of aloinfection. the virulence frequency of p. grisea isolates collected from 'primavera'' to cultivars 'brs vencedora', 'brs colosso', 'brs lideran?a', 'brs soberana', 'brs curinga' and 'brs talento', was high in descending order. on the other hand, in the fungus population of 'brs brs bonan?a' virulence frequency was high in 'brs talento', followed by 'brs curinga', 'brs vencedora', 'brs lideran?a', 'brs colosso' and 'brs soberana'. while virulence to 'brs talento' was rare among isolates from 'primavera', it was most frequent in isolates of 'brs bonan?a'. the six improved rice cultivars permitted to differentiating agriculturally important virulences in the pathogen population which can be utilized in selecting breeding lines for specific resistance, in rice blast improvement program.
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  [cached]
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.
Diversidade da virulência de Pyricularia grisea num local de melhoramento genético de arroz
Mello, Ana P. Amaral;Urashima, Alfredo S.;
Fitopatologia Brasileira , 2003, DOI: 10.1590/S0100-41582003000500012
Abstract: the objective of this investigation was to examine the virulence diversity of pyricularia grisea isolates collected from the experimental station of iac, mococa in the state of s?o paulo. the composition of races and their compatibility with known resistance genes were studied using the japanese rice (oryza sativa) differentials. fifty single spore isolates were obtained from diseased panicles of rice cultivars iac 201 and iac 4440. two races affecting upland rice cultivar iac 201, jp 137 and jp 177, and one race (jp 200) affecting the lowland rice cultivar iac 4440 were identified. the results showed low frequency of physiologic races in this breeding site. while all 25 isolates from iac 4440 were compatible to one resistance gene, pi-ta2, the isolates from iac 201 were compatible to seven out of nine known resistance genes in the japanese rice differentials. furthermore only one resistance gene (pi-zt) was effective to all isolates of p. grisae collected from rice cultivars iac 201 and iac 4440.
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.
Pathotype diversity of Pyricularia grisea from improved upland rice cultivars in experimental plots
PRABHU, ANNE S.;FILIPPI, MARTA C.;ARAUJO, LEILA G.;
Fitopatologia Brasileira , 2002, DOI: 10.1590/S0100-41582002000500005
Abstract: a study was undertaken to examine the pathogenic diversity of pyricularia grisea isolates retrieved from 14 upland rice (oryza sativa) cultivars in experimental plots during a period of five years. inoculations were performed on 32 genotypes with 85 monoconidial isolates under controlled greenhouse conditions. based on the reaction pattern of eight international differentials, eleven pathotypes of p. grisea were identified. the predominant international races or pathotypes were ib-9 (56.4%), ib-1 (16.4%) and ib-41 (11.8%). a set of eight commercial upland rice cultivars ('carajás', 'confian?a', 'maravilha', 'primavera', 'progresso', 'caiapó', 'iac-47', 'iac-201') was utilized as additional differentials for describing the virulence pattern of p. grisea. twenty-six brazilian pathotypes were identified on the basis of disease reaction on these differentials, in contrast to the 11 international pathotypes. the most predominant brazilian pathotypes, bb-21 and bb-41 were represented by 28.2% and 17.6% of the isolates tested, respectively. isolates virulent and avirulent to cultivar 'primavera' were encountered within the pathotype ib-1. utilizing brazilian cultivars as differentials, the 14 isolates of the pathotype ib-1could be further classified into eight local pathotypes, bb-41, bb-13, bb-21, bb-9, bb-29, bb-61, bd-9 and bg-1. virulence to improved rice cultivars 'canastra', 'confian?a', 'carisma', 'maravilha', 'primavera' and 'bonan?a' was frequent in pathogen population. some of the brazilian pathotypes that showed differential reaction on commercial rice cultivars could be utilized for incorporating resistance genes in susceptible cultivars improved for grain quality, by conventional breeding methods.
Pathotype diversity of Pyricularia grisea from improved upland rice cultivars in experimental plots  [cached]
PRABHU ANNE S.,FILIPPI MARTA C.,ARAUJO LEILA G.
Fitopatologia Brasileira , 2002,
Abstract: A study was undertaken to examine the pathogenic diversity of Pyricularia grisea isolates retrieved from 14 upland rice (Oryza sativa) cultivars in experimental plots during a period of five years. Inoculations were performed on 32 genotypes with 85 monoconidial isolates under controlled greenhouse conditions. Based on the reaction pattern of eight international differentials, eleven pathotypes of P. grisea were identified. The predominant international races or pathotypes were IB-9 (56.4%), IB-1 (16.4%) and IB-41 (11.8%). A set of eight commercial upland rice cultivars ('Carajás', 'Confian a', 'Maravilha', 'Primavera', 'Progresso', 'Caiapó', 'IAC-47', 'IAC-201') was utilized as additional differentials for describing the virulence pattern of P. grisea. Twenty-six Brazilian pathotypes were identified on the basis of disease reaction on these differentials, in contrast to the 11 international pathotypes. The most predominant Brazilian pathotypes, BB-21 and BB-41 were represented by 28.2% and 17.6% of the isolates tested, respectively. Isolates virulent and avirulent to cultivar 'Primavera' were encountered within the pathotype IB-1. Utilizing Brazilian cultivars as differentials, the 14 isolates of the pathotype IB-1could be further classified into eight local pathotypes, BB-41, BB-13, BB-21, BB-9, BB-29, BB-61, BD-9 and BG-1. Virulence to improved rice cultivars 'Canastra', 'Confian a', 'Carisma', 'Maravilha', 'Primavera' and 'Bonan a' was frequent in pathogen population. Some of the Brazilian pathotypes that showed differential reaction on commercial rice cultivars could be utilized for incorporating resistance genes in susceptible cultivars improved for grain quality, by conventional breeding methods.
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