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Saturation of molecular genetic map in Urochloa humidicola

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Jean Carlos de Souza Santos
Total Authors: 1
Document type: Doctoral Thesis
Institution: Universidade Estadual de Campinas, Instituto de Biologia
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Large areas of Brazil are destined for the cultivation of pasture, where the purpose is to feed cattle. These areas are occupied by various forage species, including the genus Urochloa, composed of some of the most planted species in the country, as the U. humidicola. The species is native to Africa and its main characteristics are tolerance to wetlands, the ability to resist well to heavy grazing and to acidic soils and is a hexaploid, reproducing by apomixis. A few decades ago, Embrapa started the breeding program in Urochloa, where currently many crossings have been performed in several species of the genus, including U. humidicola, where the commercial cultivar BRS Tupi was crossed with access H031, which is the only sexual genotype the Germplasm Bank of Embrapa, generating a population of 364 genotypes and 279 individuals were identified as F1 hybrids. These hybrids were used in the construction of a genetic map based on microsatellite markers, developed exclusively for the species. However, due to low map saturation, new SSR markers were developed and used to saturate the existing map. The current map was constructed with a total of 122 SSR loci, consisting of 294 markers, of which 133 were introduced by the present study. The markers were distributed in 69 linkage groups (LGs), with sizes ranging from 5,6cM to 135,5cM and with a total length of 3224,4cM. The homology groups (HGs) were formed by markers containing two or more bands linkage to the map, thereby establishing the connection between the LGs. Six HGs were obtained and two LGs remained unbound. A phenotyping for the reproduction mode was carried out in F1 hybrids and the results included in the map whose character apomixis (apo-locus) was mapped on LG2 with a distance of 23cM of Bh027.c.D2 marker. Although the new map U. humidicola is formed by the introduction of new markers, this still needs further saturated, including SNP markers, making possible to obtain a higher density map, the location bands link to the apo-locus and link to other characters of economic importance that may be mapped in the same (AU)