**5. Quantitative trait loci mapping**

Abiotic stress resistance heredity is a complicated process, QTL mapping, genetic and linkage mapping of genomic regions relevant to tolerance, is the most preferred way of discovering QTL. QTL analysis allows researchers to investigate the genetic structure of a trait. QTLs can discover genomic regions associated with the expression of the characteristic under investigation [72]. Different types of bi-parental populations are used for QTL mapping and the discovery of marker-trait associations. These populations include recombinant inbred lines (RILs), near isogenic lines (NILs), doubled haploids (DHs), multiparent advanced generation inter-cross (MAGIC), nested association mapping (NAM), and association mapping (AM) on wider panels [73]. Chickpea, pigeonpea, lentil (*Lens culinaris*), and groundnut have successfully used advanced backcross quantitative trait loci (AB-QTL). The resolution for locating novel genes, alleles, and QTLs is improved when this bi-parental mapping population is combined with GBS and GWAS [39, 74]. PEG/water deprivation stress conditions were used to create a collection of ESTs from entire plant tissues of pigeonpea [75]. From pigeonpea plants treated with 10% polyethylene glycol, two subtracted cDNA libraries were created (PEG-6000). Among the many ESTs found, three stress-responsive genes, *CcHyPRP* [76], *CcCDR* [77], and *CcCYP* [75], demonstrated extraordinary resistance to different abiotic stimuli in transgenic Arabidopsis.
