Genome scan for QTL related to bovine resistance to Boophilus microplus / Varredura genômica para QTL associados à resistência a Boophilus microplus em bovinos

AUTOR(ES)

Ana Luisa Sousa Azevedo

DATA DE PUBLICAÇÃO

2006

RESUMO

In tropical countries losses caused by bovine tick infestation have a tremendous economic impact on production systems. Genetic variation between Bos taurus and Bos 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 resistance/susceptibility in a bovine F2 population derived from the Gyr (Bos indicus) x Holstein (Bos taurus) cross. Tick resistance on each F2 animal was evaluated by counting the number of tick females after 21 days of an artificial infestation with 10,000 larvae. Blood samples of parents, F1 and F2 animals were collected for DNA extraction. Microsatellite markers were chosen from MARC USDA map to perform a genome scan in four chromosomes. Markers were chosen based on their position in the map, multi-allelism and minimum of 50% heterozygosity. A total of 21 markers were selected to cover chromosomes 13, 18, 19 and 27, with marker interval of 20 cM. This genome scan showed the presence of a QTL with additive and dominant effect (P<0.01) for tick resistance located in the end of the chromosome 18. It is not clear the origin of resistance in this QTL, since both breeds share alleles that most impact resistance or susceptibility in the F2. A putative QTL with dominant effect (P<0.07) located at 16 cM from centromere was also found on chromosome 27. The future steps after QTL mapping involve validation of these results in commercial herds of dairy cattle and beef cattle and fine mapping the position of the QTL favoring the identification of candidate genes involved with tick resistance.

ASSUNTO(S)

resistência a carrapato genetica e melhoramento dos animais domesticos quantitative traits loci boophilus microplus bovine locos de caracteres quantitativos tick resistance boophilus microplus bovino

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