Fitopatologia - Artigos

URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741

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2005 - 20093

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Autor: search.filters.author.Araújo, Leila G.Data inicial: 2005

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    Estimation of phenotypic diversity in field populations of Magnaporthe grisea from two upland rice cultivars
    (Fitopatologia Brasileira, 2007-01) Silva, Gisele B.; Zambolim, Laércio; Prabhu, Anne S.; Araújo, Leila G.; Zimmermann, Francisco J. P.
    The phenotypic diversity of Magnaporthe grisea was evaluated based on leaf samples with blast lesions collected from eight commercial fields of the upland rice cultivars 'BRS Primavera' and 'BRS Bonança', during the growing seasons of 2001/2002 and 2002/2003, in Goias State. The number of M. grisea isolates from each field utilized for virulence testing varied from 28 to 47. Three different indices were used based on reaction type in the eight standard international differentials and eight Brazilian differentials. The M. grisea subpopulations of ´Primavera' and 'Bonança', as measured by Simpson, Shannon and Gleason indices, showed similar phenotypic diversities. The Simpson index was more sensitive relation than those of Shannon and Gleason for pathotype number and standard deviation utilizing Brazilian differentials. However, the Gleason index was sensitive to standard deviation for international differentials. The sample size did not significantly influence the diversity index. The two sets of differential cultivars used in this study distinguished phenotypic diversity in different ways in all of the eight subpopulations analyzed. The phenotypic diversity determined based on eight differential Brazilian cultivars was lower in commercial rice fields of 'Primavera' than in the fields of 'Bonança,' independent of the diversity index utilized, year and location. Considering the Brazilian differentials, the four subpopulations of 'BRS Primavera' did not show evenness in distribution and only one pathotype dominated in the populations. The even distribution of pathotype was observed in three subpopulations of 'BRS Bonança'. The pathotype diversity of M. grisea was determined with more precision using Brazilian differentials and Simpson index.
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    Genetic and phenotypic diversity of Magnaporthe oryzae from leaves and panicles of rice in commercial fields in the State of Goiás, Brazil
    (Tropical Plant Pathology, 2009-03) Silva, Gisele Barata; Prabhu, Anne S.; Filippi, Marta C. C.; Trindade, Maria G.; Araújo, Leila G.; Zambolim, Laércio
    Genetic and phenotypic structure of Magnaporthe oryzae populations of two upland rice cultivars was determined. Monoconidial isolates were obtained from rice blast affected fields, four from cv. BRS Bonança and four from cv. Primavera, in Goias State (2001-2003). The pathotypes IB-41 and IB-9 were predominant in both leaf and panicle isolates of BRS Bonança and IF-1 in Primavera. A great majority of pathotypes were common to both leaf and panicle subpopulations of Bonança (42.8%) and Primavera (66.6%). The ANOVA of virulence data showed high variability within population of each cultivar. There was no significant difference in virulence pattern of isolates from leaves and panicles, independent of collection site and cultivar. The molecular characterization of isolates was done employing the rep-PCR analysis with two primer sequences from Pot2. The genetic analysis of 538 isolates showed a high genotypic diversity in both leaf and panicle pathogen populations with 103 haplotypes in Bonança and 49 in Primavera. The migration of pathotypes from leaves to panicles in each field was 70.8% and 36.6% for Primavera and BRS Bonança, respectively. The diversity of M. oryzae population was influenced by cultivar of origin. A great amount of population diversity was encountered within the same field.
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    Virulence pattern of Pyricularia grisea isolates from farmers' fields on newly released upland rice cultivars
    (Fitopatologia Brasileira, 2005-11) Araújo, Leila G.; Prabhu, Anne S.; Silva, Gisele B. da
    The virulence pattern of the isolates of Pyricularia grisea from commercial fields of the upland rice (Oryza sativa) cultivars 'Primavera' and 'BRS Bonança' was analyzed. A hundred and seventy monoconidial isolates of the pathogen virulent to 'Primavera' and 139 to 'BRS Bonança' 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 Bonança'. 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 Liderança', 'BRS Soberana', 'BRS Curinga' and 'BRS Talento', was high in descending order. On the other hand, in the fungus population of 'BRS BRS Bonança' virulence frequency was high in 'BRS Talento', followed by 'BRS Curinga', 'BRS Vencedora', 'BRS Liderança', 'BRS Colosso' and 'BRS Soberana'. While virulence to 'BRS Talento' was rare among isolates from 'Primavera', it was most frequent in isolates of 'BRS Bonança'. 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.