Hello

You need a number of generations to QTL mapping based on the software and method used. When you prepare the generations yourself, by reaching the third generation, both in terms of the number of generations is appropriate and you have reached a relative purity, so you do not go to the next generations. However, if you go to the sixth and seventh generations, you will have almost 100% purity, which is very good, but because it takes a lot of time and money, researchers usually work with the same third generation.

Best Regards

Amin

Thank you sir Amin Baghizadeh

Hello Meghraj,

The simple answer to that question is, to get most combinations out of the selected parents researchers went for the F6-F7 generations. But here's a catch, to obtain more diversity or a more diverse combination from that biparental crossing, a large quantity of material has to be put reserve. We can perform QTL analysis on F2 also. But to get dance and accurate QTL's one should be study a large quantity of phenotypic data say, >1000 plants.

Meghraj Chavhan

Early generations like F2 and F3 are segregating for many loci and hence the accurate prediction of phenotypic data is difficult as compared to genetically fixed lines in RILs.

However, considering the limitations of time and resources, early generations are generally used for coarse mapping, whereas RILs are used for fine mapping (and multi-location evaluation-based identification of stable QTLs). Sometimes, one population is used as verification/validation for the QTLs identified in the other.

Regarding the power of QTL mapping across the generations of advancement of lines, you may find this paper useful.

Mapping quantitative trait loci in F2 incorporating phenotypes of F3 progeny

by Zhang and Xu (2004). doi: 10.1534/genetics.166.4.1981

Good Luck