Family Based Mapping of Quantitative Trait Loci Using Linkage and Association Approach.

We purpose linkage and association based quantitative trait loci mapping method that plant-breeding families as a mapping population. Theoretical and empirical experiments have done to validate usefulness of family based linkage and association mapping method in breeding context. Empirical validation of the family-based linkage and association analysis was done to map the QTL, Fhb1, responsible for Fusarium head blight resistance in hexaploid wheat using 82 families from a spring wheat breeding program. The validated Linkage mapping procedures included variance component method and pedigree-wide regression. Similarly, Quantitative transmission disequilibrium test (QTDT) was used to test association between marker and trait of interest. Both linkage and association approach successfully identified the known QTL location with a high probability value. Beside empirical validation, simulation studies were done to optimize the QTL mapping process. The power to detect QTL depends upon family size, family type, marker density, variance explained by the QTL and the level of significance. The average power to detect QTL was compared with Recombinant inbred line (RIL) populations. The method has advantage of using typical plant breeding families from a typical plant breeding program, reducing cost and time to develop mapping populations. The mapping approach can accelerate speed of the QTL mapping. Besides QTL mapping, the method will help in performing marker validation, QTL introgression and marker-aided selection in the same population simultaneously. Moreover the mapping population is likely to give rise to new cultivar. The mapping methods are being tested to map new resource of resistance. Also simultaneous marker aided selection in early and advanced generation are underway.