The cotton cultivar DELTAOPAL is resistant under field as well as under glasshouse conditions to the Brazilian isolates of Xanthomonas axonopodis pv. malvacearum (Xam). Segregating populations derived from the cross b...The cotton cultivar DELTAOPAL is resistant under field as well as under glasshouse conditions to the Brazilian isolates of Xanthomonas axonopodis pv. malvacearum (Xam). Segregating populations derived from the cross between this cultivar and one susceptible cv. BRS ITA 90, were utilized to identify molecular marker linked with the resistance gene to Xam by “Bulk Segregant Analysis (BSA)”. Two hundred and twenty microsatellite (Single Sequence Repeat—SSR) primers were tested. The amplification products were visualized in polyacrylamide gels stained with silver nitrate. Only one primer was informative and showed polymorphism between the DNA of the parents and their respective bulks of homozygous F2 populations contrasting for resistance and susceptibility, and hence was used to analyze DNA of 120 F2 populations. The microsatellite primer yielded one band of 80 bp linked with the resistance locus, which was absent in the susceptible parent as well as in the bulk of the homozygous susceptible plants of the cross. The segregation ratio as determined by phenotypic analysis was 3R:1S. It is believed that the microsatellite marker was linked with the resistance locus and hence may offer new perspectives for marker assisted selection against the angular leaf spot disease of cotton. It is however, felt necessary to repeat the microsatellite analysis and make sure that the primer is tightly linked with the resistance locus and at the same time verify the genetic distance between the marker and the resistance locus.展开更多
Genotypic and phenotypic variation among 16 isolates of Ramularia areola of Gossypium hirsutum collected from five different geographical regions of Brazil was studied through virulence spectrum on three cultivars in ...Genotypic and phenotypic variation among 16 isolates of Ramularia areola of Gossypium hirsutum collected from five different geographical regions of Brazil was studied through virulence spectrum on three cultivars in the glasshouse and through ERIC- and REP-PCR and ITS1-5.8S-ITS2 rDNA analysis. Difference in virulence spectrum and molecular analysis of some isolates was observed. ERIC- and REP-PCR showed similar results and revealed a high level of diversity among the isolates. A unique profile for both ERIC and REP was obtained for most isolates. On the other hand, the ITS rDNA analysis did not show different PCR-RFLP patterns. While some isolates differed among each other considering genotypic and phenotypic reactions, no clear cut evidence was found about the existence of genetic lineages of R. areola in Brazil. Identification of genetic variability among the R. areola isolates originated from different geographic regions would permit screening of Brazilian germplasm and achieve sources with a wide spectrum of resistance. This is the first report of the genotypic and phenotypic variability among the R. areola isolates originated from five cotton growing regions of Brazil.展开更多
基金The present research was conducted under the financial support of IMA,MT,Brazil.
文摘The cotton cultivar DELTAOPAL is resistant under field as well as under glasshouse conditions to the Brazilian isolates of Xanthomonas axonopodis pv. malvacearum (Xam). Segregating populations derived from the cross between this cultivar and one susceptible cv. BRS ITA 90, were utilized to identify molecular marker linked with the resistance gene to Xam by “Bulk Segregant Analysis (BSA)”. Two hundred and twenty microsatellite (Single Sequence Repeat—SSR) primers were tested. The amplification products were visualized in polyacrylamide gels stained with silver nitrate. Only one primer was informative and showed polymorphism between the DNA of the parents and their respective bulks of homozygous F2 populations contrasting for resistance and susceptibility, and hence was used to analyze DNA of 120 F2 populations. The microsatellite primer yielded one band of 80 bp linked with the resistance locus, which was absent in the susceptible parent as well as in the bulk of the homozygous susceptible plants of the cross. The segregation ratio as determined by phenotypic analysis was 3R:1S. It is believed that the microsatellite marker was linked with the resistance locus and hence may offer new perspectives for marker assisted selection against the angular leaf spot disease of cotton. It is however, felt necessary to repeat the microsatellite analysis and make sure that the primer is tightly linked with the resistance locus and at the same time verify the genetic distance between the marker and the resistance locus.
基金The present research was conducted under the financial support of IMA,MT,Brazil.
文摘Genotypic and phenotypic variation among 16 isolates of Ramularia areola of Gossypium hirsutum collected from five different geographical regions of Brazil was studied through virulence spectrum on three cultivars in the glasshouse and through ERIC- and REP-PCR and ITS1-5.8S-ITS2 rDNA analysis. Difference in virulence spectrum and molecular analysis of some isolates was observed. ERIC- and REP-PCR showed similar results and revealed a high level of diversity among the isolates. A unique profile for both ERIC and REP was obtained for most isolates. On the other hand, the ITS rDNA analysis did not show different PCR-RFLP patterns. While some isolates differed among each other considering genotypic and phenotypic reactions, no clear cut evidence was found about the existence of genetic lineages of R. areola in Brazil. Identification of genetic variability among the R. areola isolates originated from different geographic regions would permit screening of Brazilian germplasm and achieve sources with a wide spectrum of resistance. This is the first report of the genotypic and phenotypic variability among the R. areola isolates originated from five cotton growing regions of Brazil.
