Made available in DSpace on 2014-12-17T15:18:13Z (GMT). No. of bitstreams: 1 ValeskaSL.pdf: 346083 bytes, checksum: 77d65411fbea9e85070d5c90e9b52fef (MD5) Previous issue date: 2007-02-23 / This research was conducted with the aim to study the genetic and pathogenic structure of Ramularia areola isolates collected in Brazil and to characterize the resistance response in cotton plants to ramularia spot. The genetic variability of 28 isolates of R. areola was studied using RAPD markers. The pathogenicity evaluation was realized by the inoculation of 6 isolates on cotton varieties Guazuncho-2 (Gossypium hirsutum) and VH8-4602 (Gossypium barbadense). The inheritance of disease resistance was studied using an artificially inoculated population of F2 individuals derived from the intercross of Guazuncho-2 (susceptible variety) end VH8-4602 (resistant variety), and also the parents and F1 individuals. Molecular polymorphism between the G. hisutum varieties DeltaOpal (suscetible) and CNPA CO-11612 (resistant) was estimated by 118 SSR and 24 AFLP markers. The parental genotypes Guazuncho-2 and VH8-4602 were selected for mapping, and then Recombinant Inbred Lines (RIL?s) derived from this crossing were evaluated with SSR 12 markers. The analysis of population structure of R. areola revealed that the three subpopulations were genetically simillar (Gst=0.18), and the isolates from Goi?s and Minas Gerais were more similar to each other (0,92). This probability can be related to the relatively high gene flow among the three subpopulations (Nm=2.20). The isolates R. areola 9.1, from Minas Gerais State and 8.1 and 8.3 from Goi?s State were the most aggressive ones to the susceptible variety Guazuncho-2. The variety VH8-4602 presented high level of resistance to ramularia spot. No differential interaction was observed between the pathogens and the analyzed varieties, and the resistance was classified as horizontal. The quantification of disease by number of necrotic lesions and number of spores in individual plants of F1 and F2 generations from the crossing between the varieties Guazuncho-2 and VH8-4602 presented continuous distribution, suggesting polygenic resistance. The resistance is probabilly recessive, since necrotic lesions and sporulation were observed on F1 plants. The molecular polymorphism between DeltaOpal e CNPA CO-11612 lineages was low (6%), then would be difficult to accomplish molecular mapping of disease resistance using this intercross. With the genotyping of the RIL s it was verified that 25% of the markers segregated in the proportions proposed by Mendel s Law and 75% of the studied markers presented segregation distortion in favor to the parental G. hirsutum. Both the low genetic variability of the pathogen and the number of resistance genes suggest that durable genetic resitance may be achieved / Este estudo teve como objetivos estudar a estrutura gen?tica e patog?nica de isolados de Ramularia areola do Brasil e caracterizar a resposta de resist?ncia no algodoeiro ? mancha-de-ramul?ria. Foi avaliada a variabilidade gen?tica de 28 isolados do pat?geno, utilizando-se marcadores RAPD. A avalia??o da patogenicidade de 6 desses isolados foi realizada ap?s a inocula??o nas variedades Guazuncho-2 (Gossypium hirsutum) suscet?vel e VH8-4602 (Gossypium barbadense) resistente ? doen?a. A heran?a da resist?ncia no algodoeiro ? doen?a foi caracterizada pela medi??o de intensidade da doen?a nas variedades Guazuncho-2 (G. hirsutum), suscet?vel, e VH8-4602 (G. barbadense), resistente ? doen?a, e nas gera??es F1 e F2 provenientes do cruzamento entre elas. O polimorfismo molecular entre as linhagens de G. hirsutum DeltaOpal e CNPA CO11612, contrastantes fenotipicamente quanto ? resist?ncia ? doen?a foi avaliado utilizando-se 118 marcadores SSR e 24 AFLP. Para mapeamento molecular dos genes de resist?ncia, linhagens recombinantes RIL s derivadas do cruzamento entre Guazuncho-2 e VH8-4602 foram genotipadas utilizando marcadores SSR. A an?lise da estrutura da popula??o de R. areola revelou que as tr?s subpopula??es foram semelhantes geneticamente (Gst=0.18). Os isolados de Goi?s e Minas Gerais obtiveram maior similaridade gen?tica (0,92), que pode estar associada com o alto fluxo gen?tico existente entre as subpopula??es que foi de (Nm=2.20). Quanto ? patogenicidade, os isolados de R. areola 9.1, coletado no estado de Minas Gerais, 8.2 e 8.3 de Goi?s, foram mais agressivos na variedade suscet?vel Guazuncho-2. A variedade VH8-4602 apresentou alto n?vel de resist?ncia ? doen?a. N?o foi observada intera??o diferencial entre os pat?genos e as variedades analisadas, sendo a resist?ncia classificada como horizontal. Na an?lise dos indiv?duos das gera??es F1 e F2, provenientes do cruzamento entre Guazuncho-2 e VH8-4602, a quantifica??o de sintomas da doen?a atrav?s da contagem de manchas necr?ticas e pelo n?mero de esporos mostrou varia??o cont?nua da resist?ncia ? doen?a nos indiv?duos da gera??o F2, indicando que a heran?a ? polig?nica. O aparecimento de sintomas e esporula??o nos indiv?duos F1 mostrou que a resist?ncia ? recessiva. O polimorfismo molecular entre as linhagens de G. hirsutum, DeltaOpal e CNPA CO11612 foi de 6%, portanto baixo, para realizar o mapeamento. Durante genotipagem das RIL?s foi verificado que 25% dos marcadores segregaram de acordo com as propor??es das leis de Mendel, e 75% desses marcadores apresentaram distor??o de segrega??o, com aumento da propor??o de genes do parental G. hirsutum. A baixa variabilidade do pat?geno e n?mero de genes de resist?ncia sugere que a resist?ncia gen?tica ao pat?geno tenha alta durabilidade