Detecção de QTL para resistência ao carrapato Riphicephalus (Boophilus) microplus por meio de varredura genômica em bovinos

• Autor(a) principal: Azevedo, Ana Luisa Sousa
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1393
• topic: Microssatélite; Quantitative trait loci; Microsatellite; Quantitative trait loci; CNPQ::CIENCIAS BIOLOGICAS::GENETICA::GENETICA ANIMAL

ln tropical countries losses caused by bovine tick infestation have a tremendous economic impact on production systems. The different levels of tick resistance between B. p. taurus e B. p. indicus is well documented. Genetic variation between Bos p. taurus and Bos p. indicus to tick resistance and molecular biology tools might facilitate the use of molecular markers linked to resistance traits as an auxiliary tool in selection programs. The objective of this work was to identify QTL associated with tick R. (B.) microplus resistance/susceptibility in a bovine F2 population derived from the Gyr (B. p. indicus) x Holstein (B. p.taurus) cross. Artificial infestations with tick were conducted to determine the level of resistance of each F2 animal. Evaluations were performed in two seasons, dry and wet. A total of 109 microsatellite markers were selected from MARC/USDA map to cover chromosomes 1, 2, 3, 4, 6, 8, 9, 10, 11, 12, 15, 16, 17, 20, 22, 25 e 28 in 20 cM intervals. Association studies indicated the presence of significant QTL in four chromosomes. ln each season distinct response patterns were found for most detected QTL. A dominant QTL (PC <0.01) was found in the central region of BTA2 for the dry season. Three QTL were detected on BTA6 (Pc <0.05). The one located in the beginning of the chromosome showed the same pattern in both dry and wet seasons. The QTL located close to 40 cM was detected only in wet season and the QTL located close to 100 cM was detected only in dry season. All QTL detected on BTA6 showed additive effect with the tick resistance derived from Gir breed. Two additive QTL were detected (Pc <0.01) on BTA1O for wet season. The highest significant F value (16.5) was detected at 43 cM position on BTA 11 showing a highly significant QTL with additive effect (Pc <0.01) for dry season. This QTL alone is responsible for 5,02% of the trait phenotypic variance. Highly significant detected QTL should be saturated with additional markers and also validated in commercial herds.