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Plant Breeding Approaches in Developing Stress Tolerance

2015). Transgenic approaches improve crop genetic makeup by introducing

resistant genes against stresses (Mishra et al., 2016). Transgenic strawberry

is resistant to Strawberry mild yellow edge potexvirus (Silva et al., 2015).

Similarly, the coat protein gene in transgenic chili has made chili resistant

to many diseases caused by viruses (Praveen et al., 2017). The virus coat

protein gene in Citrullus lanatus has made Zucchini yellow mosaic virus

(Harth et al., 2017). p transgenic tomato developed by RNAi technique has

made tomato resistant to tomato leaf curl virus.

6.5.3.2 TRANSGENIC APPROACHES FOR ABIOTIC STRESS

6.5.3.2.1 Transgenic Approaches for Drought Stress

In plants, many regulatory genes, including transcription factors (TFs), can

express a lot of downstream and many other genes for abiotic stress toler­

ance (Marco et al., 2015). For transgenic approaches, many transcription

factors such as MYB, NAC, and MYC have been used for abiotic stress

tolerance in crop plants (Marco et al., 2015). Transgenic tomato having gene

from Arabidopsis C-repeat binding factor/dehydration-responsive element-

binding in the expression of 35s, and nos showed tolerance to drought stress

in comparison to the non-transgenic tomato (Kidokoro et al., 2015). In the

same way, transgenic apple plants have shown tolerance against drought

stress due to the expression of the MYB TFs compared to the non-transgenic

apple (Buti et al., 2018). Similarly, transgenic grapevines with the DREB1b

gene have shown tolerance against drought stresses than the non-transgenic

grapevine.

WRKYTFs are the other set of the TFs which showed the positive regulated

abiotic stress in crop plants, and these are exploited in a wide range against

abiotic stress tolerance (Jiang et al., 2017). Many types of research showed

that WRKY TFs are involved in creating drought stresses tolerant plants. For

instance, transgenic Chrysanthemum morifolium plants are drought tolerant

due to the ABA-mediated pathway, which activates many downstream genes

like DREB1A, MYB2, and ABI2. In other research, transgenic bananas

having the WRKY71 gene had made tolerant to much abiotic stress (Zhou

et al., 2015). Similarly, NAC TFs having three TFs (no apical meristem (N)/

Arabidopsis transcription activator factor (A)/cup-shaped cotyledon (C)) are

used to develop transgenic crop plants which are tolerant to a lot of abiotic

stress (Hong et al., 2016). In many studies, the development of the transgenic