Due to the recent development of molecular breeding technology, bulked segregant analysis has also made a great progress. The pooled DNA analysis can be used for two contrasting groups of individuals from any population, not just for those from biparental  segregating populations.
to develop DNA markers, the first important step is to select or produce appropriate breeding populations.  Nearly isogenic lines(NILs) are frequently used to select DNA markers in self-pollinating plants, though significant time and effort are required to develop NILs via backcrossing.  A novel method bulked segregant analysis (BSA) was developed for efficient marker isolation and is based on a plant population comprising both dominant and recessive segregants for target traits.  When comparing the bulked segregants with other breeding populations such as NILs, bilked segregant populations may be developed more quickly in the F2 generation by first dividing them into two pools of dominant and recessive individuals.  The two pools differ in their allelic content only at the chromosomal region near the target gene.   \cite{2005}
The BSA method has frequently been used in Brassica because it is difficult to develop NILs in these species. In the following sections, we discuss several DNA markers for fertility restoration (Rf) genes fro cytoplasmic male sterility (CMS) in Brassica.
In contrast to the diploid species, linkage maps of allotetraploids constructed only RFLP markers do not completely cover the entire genome, partly because the genome is typically larger than that of their ancestors.  However, since these initial studies were constructed,  PCR techniques have become more common and PCR-based DNA markers have since become deeply integrated into marker technologies.\cite{2005}