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Universidade Federal do Rio Grande do Sul (2008)

Análise da diversidade genética e avaliação de características morfofisiológicas associadas à tolerância à seca em diferentes genótipos de trevo branco (Trifolium repens L.)

Bortolini, Fernanda

Titre : Análise da diversidade genética e avaliação de características morfofisiológicas associadas à tolerância à seca em diferentes genótipos de trevo branco (Trifolium repens L.)

Genetic diversity analysis and evaluation of morphophysiological traits associated with drought tolerance in different genotypes of white clover (Trifolium repens L.)

Auteur : Bortolini, Fernanda

Université de soutenance : Universidade Federal do Rio Grande do Sul.

Grade : Doutor em Zootecnia 2008

Résumé
White clover (Trifolium repens L.) it is one of the most important forage legumes in temperate regions of the world, being one of the most used species in pastures during the winter and spring in Rio Grande do Sul, which has persistence problems, mainly in the summer, due to the high temperatures and the low water availability in that period. The work was aimed to analyze the genetic diversity among the accessions from the white clover core collection obtained from the United States Department of Agriculture (USDA) through isozymes and microsatellite markers, besides evaluating the effect of water availability (90 and 50% of the soil moisture field capacity) on morphophysiological traits of a sample of the collection. The accessions were analyzed through 18 isozyme bands (esterase) and nine microsatellites loci (SSR), which were efficient to detect the high existent genetic diversity among the accessions. A total of 70 SSR fragments was analyzed, obtaining an average of 7,8 alleles per locus and, a PIC varying from 0,26 to 0,86, with average of 0,67. The medium genetic distance through Nei’s coefficient for the esterase data was 0,73, varying from 0 to 1,79, evidencing five groups formed for the 47 analyzed accessions, while for SSR the medium distance was 0,68, varying from 0,18 to 2,25, classifying the 81 accessions in seven groups. In relation to drought tolerance, there was interaction genotype x level of water for 12 of the 23 measured variables in the first evaluation, and 19 of the 32 variables analyzed in the second. The best accessions under water deficit were 75 and 74, which triplicate and double, respectively, the water use efficiency, showing larger internodes length and consequently larger productions of MSPA. Therefore this work represents a contribution to the study of the genetic variability and to the characterization of the accessions of the core collection of the specie, through biochemical and molecular markers, as well as through morphophysiological markers under water stress conditions.

Assunto(s) : Trevo branco, Leguminosa forrageira, Genetica vegetal, Diversidade genética

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