Quantitative trait loci （QTL） were detected for 8 internal organ traits, 3 carcass length traits, and teat number trait in 214 pigs in a resource population that included 180 F2 individuals. A total of 39 microsatellite markers were examined on SSC4, SSC6, SSC7, SSC8, and SSC13. The genetic traits included heart weight （HW）, lung weight （LW）, liver and gallbladder weight （LGW）, spleen weight （SPW）, stomach weight （STW）, small intestine weight （S1W）, large intestine weight （LIW）, kidney weight （KW）, carcass length to the first cervical vertebra （CL1）, carcass length to the first thoracic vertebra （CL2）, rib numbers （RNS）, and teat numbers （TNS）. Results indicated that, 3 highly significant QTL （P≤0.01 at chromosome-wise level） for HW （at 30 cM on SSC6）, RNS （at 115 cM on SSC7）, TNS （at 110 cM on SSC7）, and 6 significant QTL （P≤0.05 at chromosome-wise level） for LW （at 119 cM on SSC13）, LGW （at 94 cM on SSC6）, SPW （at 106 cM on SSC8）, SIW （0 cM on SSC4）, LIW （170 cM on SSC 4）, and TNS （at 95 cM on SSC6） were detected. The phenotypic variances for which these QTL were accounted ranged from 0.04 % to 14.06 %. Most of these QTL had not been previously reported.
Live measurement growth traits are very important economic traits in pig production and breeding. In this research, quantitative trait loci （QTL） were detected for 11 live estimated growth and carcass traits, including birth weight （BWT）, average daily gain over testing periods （ADG3）, live backfat thickness at last 3-4th lumbar （LBFT3）, live loin eye area （LLEA）, and so on, in 214 pig resource family population, including 180 F2 individual, by 39 microsatellite marker loci on SSC4, SSC6, SSC7, SSC8, and SSC13. The results indicated that 4 chromosome significant level QTL and one suggestive QTL were detected for ADG3 （at position of 50 cM on SSC8）, LBFT3 （at position of 147 cM on SSC4）, LLEA （one highly significant at position of 48 cM on SSC7; another significant at position of 125 cM on SSC8） and BWT （suggestive significant at position of 0 cM, at marker sw489 on SSC4）. The phenotypic variance of these QTL accounted for 0.95% to 16.91%. Most of them were mentioned in previous reports; except the QTL of LLEA at position of sw1953 on SSC8 which maybe a new QTL.
To investigate the correlation of individual heterozygosity and heterosis of three traits in crossbred F1 pig populations, the F1 populations were built by random mating Yorkshire x Meishan （YM, n = 82）, and its reciprocal （MY, n =47） and two straightbred populations （Yorkshire = 34, Meishan = 55） were used as control groups. The heterosis of birth weight （BWT）, average daily gain （ADG）, and feed conversion ratio （FCR） were acquired as well. In the research, the significant marker loci for the heterosis of the three traits were observed by one-way ANOVA （P〈0.01） in a total of 39 marker loci on SSC4, SSC6, SSC7, SSC8, and SSC13, and the numbers of the significant marker loci were 12 （BWT）, 18 （ADG）, and 17 （FCR）, respectively, based on which the general heterozygosity （GH） was divided into significant marker loci heterozygosity （SH） and insignificant marker loci heterozygosity （IH）. Furthermore, the trends of alteration in heterosis with the stepwise increase in heterozygosity by 0.05 were explored. This was done by the regression analysis of the three kinds of heterozygosity against heterosis of the three traits. The results showed that, for BWT, the heterosis increased with the increase in GH （r=0.9337, P=0.0021） and SH （r=0.9165, P=0.0102）; for ADG, the heterosis increased with the increase in IH （r=0.7012, P=0.0353） and GH （r=0.7470, P=0.0537, near significant）; for FCR, the heterosis of feed efficiency increased with the increase in IH （r=0.8721, P=0.0022）. The results indicated that the correlation was not always higher or more significant for SH with heterosis than it was for IH or GH with heterosis, and it might be because of the reciprocal cancellation of the positive effect and negative effect of QTL linked to the significant marker loci.
ZHANG Jing-huXIONG Yuan-zhuDENG Chang-yanJIANG Si-wenLEI Ming-gangLI Jia-lianLI Feng-eZHENG Rong
