GROWTH ON CHROMOSOME 4 IN PIGS. K. M. Silva1, S. E. F. Guimarães1, P. S. Lopes1,. M. V. G. B. Silva2, M. S. Pereira1. 1 Departamento de Zootecnia, ...
8th World Congress on Genetics Applied to Livestock Production, August 13-18, 2006, Belo Horizonte, MG, Brasil
DETECTION OF QUANTITATIVE TRAIT LOCI (QTL) FOR GROWTH ON CHROMOSOME 4 IN PIGS K. M. Silva1, S. E. F. Guimarães1, P. S. Lopes1, M. V. G. B. Silva2, M. S. Pereira1. 1
Departamento de Zootecnia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil, 36571-000 and 2 Centro Nacional de Pesquisas em Gado de Leite (Embrapa-CNPGL), Juiz de Fora, Minas Gerais, Brazil, 36038-330. INTRODUCTION The development of molecular biology techniques and the application of these techniques to farm animals have progressed rapidly and have opened new vistas for investigators wishing to identify genes that control quantitative traits (quantitative trait loci or QTL) of economic importance. In pig breeding, QTL have been identified using intercrosses between divergent populations. The first QTL mapping in pigs used a Wild Boar x Large White Cross (Anderson et al., 1994) and revealed significant effects of QTL on pig chromosome 4. Since them, numerous studies were performed to locate QTL in pigs. In adition, the number of markers described for the pig map has increased rapidly from 28 loci in 1984 (Echard, 1984) to aproximately 4080 loci, among which there are aproximately 1588 genes (htpp://www.thearkdb.org; January 2006). The search for QTL can use the entire genome (Anderson et al., 1994; Geldermann et al., 2003) or focus on individual chromosomes (Wang et al., 1998) or candidate genes (Rothschild et al., 1996). The objetive of this study was to search the pig chromosome 4 for QTL affecting growth traits using a experimental F2 cross between Brazilian naturalized Piau and commercial pig breeds. MATERIAL AND METHODS A F2 population of 800 animals was derived from the mating between two Brazilian naturalized Piau boars and 18 commercial dams. All animals were weighed and performance tested individually. The growth traits analyzed were body weight at birth, 21, 42, 63, 77 and 105 days of age, as well as feed intake, feed gain ratio, average daily gain from 77 to 105 days of age and weight at slaughter. The traits considered in this analysis, along with the number of F2 individuals with records for each trait, QTL position and F-value are given in Table 1. The F2, F1 and F0 animals were typed for 13 markers on chromosome 4. Specifically, the markers were SW2404, S0227, SW489, S0301, S0001, SW35, SO217, S0073, S0214, SW524, SW445, SW58 and SWR153. PCRs were carried out in an MJ Research Thermal Cycler. The microssatellte PCR products were analysed with Genescan software on capillary eletrophoresis equipament with fluorescence detection (ABI PRISM 310 Genetic analyser). The number of alleles for each marker varied from 2 (SW524) to 10 (SW445). The interval analysis for informative markers on chromosome 4 was conducted using a regression approach originally described by Haley and Knott (1992). A web based version of this regression interval mapping method is available (Seaton et al., 2002). The software used to analyze data from F2 family was QTL Express (http://qqtl.cap.ed.ac.uk).
8th World Congress on Genetics Applied to Livestock Production, August 13-18, 2006, Belo Horizonte, MG, Brasil
Table 1. Traits analyzed with their mean, standard deviation, number of individuals with records for each trait, QTL position and F-value. Trait No. F2 Birth weight (kg) PN 800 Weight at 21 days of age (kg) P21 665 Weight at 42 days of age (kg) P42 665 Weight at 63 days of age (kg) P63 656 Weight at 77 days of age (kg) P77 602 Weight at 105 days of age (kg) P105 595 Feed intake (kg)A CR 598 A Average daily gain (kg) GPD 591 Feed gain ratio (kg/kg)A CA 591 Slaughter weight (kg) PA 510 A
Mean 1,20 4,87 8,25 16,21 21,42 36,26 39,81 0,53 2,80 64,75
SD LocationB F-value 46 2,15 0,28 1,18 45 ; 99 7,09*; 6,29* 125 2,69 1,99 125 2,26 3,43 70 3,74 4,38 90 4,52 6,74 106 1,09 8,36 87 3,16 0,14 10 4,38 0,65 125 2,64 5,63
Traits measured from 77 to 105 days of age; B QTL position (cM); * Significant at the 5% genome-wide level.
RESULTS AND DISCUSSION The 13 markers genotyped in this study show average marker spacing of 10,7 cM. The map covered almost all of SSC4, with the most proximal marker, SW2404, mapping to position 0 cM and the most distal, SWR153, to position 125,6 cM. The data from this study provided significant evidence (P
