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with traits or not, GWAS mainly focuses on connections between traits and

SNPs (Manolio, 2010). GWAS is considered as a powerful and ubiquitous

tool which has been used in the study of complex traits. GWAS is being

effectively and efficiently used for genome–phenotype association studies

and used to investigate or in identifying a disease either in plant or animal.

Although NGS technology is still in its early stages of development, it

has proven to be a reliable method for identifying genetic diversity across the

genome. Single nucleotide polymorphisms (SNPs), insertions, and deletions,

and copy number changes, all of which are linked to growth and develop­

ment as well as stress responses. SNPs, insertions, and deletions, and copy

number changes are all examples of genetic variants. NGS has been used in

conjunction with GWAS to find potential molecular markers. The research of

comparative genomics is aided by NGS technology, which allows studies of

variety within and across species discussed later in the chapter.

10.2 PLANT RESPONSE TO VARIOUS ENVIRONMENTAL STRESSES

Stresses are generally occurred by the conditions in which the plants are

placed, and these stresses affect the plant’s growth and mechanisms (Verma

et al., 2013) that lowers the plants productivity. The major alterations are

done in the healthy plant by different stresses and these alterations trigger

the most of the responses like changes in the growth and development rate

of the plant, their gene expression, altered cellular metabolism, and yields

of plants or crops. Plants usually react to the changed environment and

these sudden changes in plants show the restored environmental conditions

or we can describe that plants are encountered with this diverse range of

environmental stresses, which ultimately affect their productivity. The plant

stresses are majorly categorized into two types: (i) abiotic stresses; and (ii)

biotic stresses. The abiotic stresses cover two major subunits physical and

chemical. Light, water, salinity temperature comes under physical subunits.

While, the pesticides, pollutants, and toxic heavy metals (Seneviratne et

al., 2019) are some of the chemical forms of stress. Whereas the insecti­

cides, diseases (Verma et al., 2013), capturing through herbivorous animals

(Morkunas et al., 2018) majorly comes in the biotic form of stresses. Both

the stresses show different impacts on plants, but salinity, temperature, and

drought impose major impacts (Figure 10.1). These adversely affect not

only their growth and productivity, but they destroy or injured them to their

depth, because of which their metabolic dysfunctioning starts (Verma et al.,