数量遗传课件.ppt

The Use of Molecular Genetics in the Improvement of Agricultural Populations Past and CurrentSelection Strategies Integration of molecular data Processes that create Linkage Disequilibrium Mutation Selection Drift (inbreeding) Migration and crossing Processes that create Linkage DisequilibriumCrossing LD is continuously eroded by recombination Erosion of LD by recombination Novel LD extends over large distances Implications for QTL detection and MAS Combining Phenotypic andMolecular Data in Selection Gains from MAS Meuwissen Goddard, 1996QTL with 1/3 of genetic variance haplotype-markedh2=.27 Gains from MAS Effect of Heritability (Meuwissen Goddard 1996) Single marked QTL with 1/3 of genetic variance Use of MAS atexistingselection steps MA-pre-selectionQTL variance = 20% MA-pre-selectionQTL variance = 20% Long-term effects of MAS a=1sg h2=0.25 20% selected QTL frequency = 5% MAS in Cross-breeding Programs MAS in Cross-breeding Programs Genetic Model Maximize CDRover 10 generations Processes that create Linkage DisequilibriumMutation and Selection Processes that create Linkage DisequilibriumRandom drift/inbreeding Combining Phenotypic andMolecular Data(Lande Thompson, 1990) q m q m q M q M q M q m q m q M q m q M q m q m Q M Q M q m q M Q M Q M q m q M q m q M q m q m Q M Selec- tion Q2 M Q1 Selection on Marker Score Based on Zhang and Smith (1992) 30 replicates Genetic progress in a cross between inbred lines Based on Zhang and Smith (1992) 30 replicates Mol.S BLUP Index Estimation of QTL effects Line 2 F1 F1 x x F2 F2 x F3 F3 x QTL detection and selection - overestimation - re-estimate - adjust - threshold? Re-estimation of QTL effects - significant only - all Use LD linkage information Line 1 Marker-assisted Composite Line Development QTL detection MAS L1 L2 F1 F1 x x F2 L2 x BCF3 BCF3 x MAS . . MAS within breeds Using within-breed LD Marker-assisted pure line selection Using popula