小中大关联分析是基于linkage disequilibrium, also called linkage disequilibrium mapping.
conventional QTL dessecting is based on linkage, also called linkage mapping. association mapping utilizes historical recombination events to locate QTLs, in which no pedigree population is needed convers versus to use natural population.
alternative methods can be select due to whether the interesting trait is a qualitative or a quantitive trait. In animal, i think you maybe use case-control analysis. Firstly, you should analysis the structure of LD in your targeting specie. with which information, you can estimate appropriate marker density to cover genome. that's important.
so many references and help resources in the internet, you may have not t
ried to search by yourself.