Study On Prediction Of Heterosis Of Partial Traits By Using Microsatellite Markers

Genetic variability of seven pig populations (Landrace L, Large White W, Duroc D, LW, WL, DLW, WLW) were detected by using 8 microsatellite markers in this study. Average genetic heterozygosity and parental genetic distance were calculated according to frequencies of these alleles. At the same time, correlations between average genetic heterozygosity, parental genetic distance and heterosis of partial traits (daily gain, back fat thickness, lion eye area, lean percentage, lat percentage) were analyzed. The results show as fellows:1. Generally, heterosis of WL is superior to that of LW, heterosis of WLW is identical with that of DLW.2. 8 microsatellite loci linked daily gain QTL (SW524 and SW58 of them linked back fat thickness QTL) generated a total of 114 alleles in seven pig populations, means number of alleles per locus is 14.25. Mean polymorphism information content(PIC) per locus is from 0.6121 to 0.8020( > 0.5).Mean effective number of alleles per locus is from 3.185 to 6.144(>2). These mean 8 microsatellite loci used in this study is high polymorphism.3. With effective number of alleles, polymorphism information content, average heterozygosity, parental genetic distance, genetic diversity of four crossing combination populations were analyzed. The four parameters had similar tendencies among each population. DLW had the highest values, followed by LW, WL, WLW combination.4. Parental genetic distance and average genetic heterozygosity evaluated by using 8 microsatellite markers linked daily gain QTL show positive correlations of high level with hetelosis of daily gain and lean Percentage (0.969CK 0.9936, 0.9909, 0.9741, respectively) regardless of back-crossing combination, but positive (negative) correlations of moderate level with back fat thickness >, loin muscle area-, fat percentage (-0.6480,-0.5530, 0.4541 ^ 0.3496, -0.5189, -0.4181, respectively) ,and the effect of effective markers to the accuracy of prediction of heterosis was discussed. Added back-crossing combination, the correlations between average genetic heterosygosity, parental genetic distance and heterosis of 5 traits is decreased. For example, the coefficient of the correlation between average genetic heterosygosity, parental genetic distance and daily gain heterosis is only 0.1512 and 0.3298 respectively, and the effect of genetic background to the accuracy of prediction of heterosis was discussed. At the same time , the correlation was analyzed analogically by using 2 microsatellite linked backfat thickness QTL. No changes were found at all, their causes were analyzed.5. Parental genetic distance shows positive correlation of high level with average genetic heterosygosity(r>0.9).6. Molecular mechanism of heterosis was studied. It was suggested that the essence of interaction between genes is the changes of gene expression and regulation, which causes whether heterosis is generated or not.7. The results show predication of heterosis by using molecular markers is conditional. The study develops feasible solution and its theoretical criteria for prediction of heterosis.