Biology and Biotechnology of Environmental Stress Tolerance in Plants (Aryadeep Roychoudhury)

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Biology and Biotechnology of Environmental Stress Tolerance in Plants, Volume 3

the recombination frequency, the gap between different markers can be

calculated; therefore, the position of different QTLs in a specific genome can

also be calculated (Collard et al., 2005). In the wheat plant about 10 QTLs

for yellow rust resistance have been identified by the help of QTLs mapping.

Among these 10 QTLs, the 05 major QTLs are QYr.sgi-4A.1, Lr34/Yr18,

QYr.sgi-2B.1a, QYr.sgi-4A.2, and QYr.sgi-2B.1 (Chu et al., 2009).

6.5.2 MARKER-ASSISTED SELECTION

In plants, breeding approaches DNA markers to play an essential role in

identifying and selecting plants with the suitable trait (Roychowdhury, 2014;

Roychowdhury et al., 2014). Owing to a large number, these DNA markers

are used in a wide range to study and identify plants and these markers are

neutral as they are present in the coding region. The DNA markers which are

used in a wide range are simple sequence repeats (SSR), restriction fragment

length polymorphisms (RFLP), amplified fragment length polymorphisms

(AFLP), and random amplified polymorphic DNA (RAPD) (Collard et al.,

2005). The marker-assisted selection also plays an important role in the

germplasm screening for resistant genes (Simon-Mateo & Garcia, 2011). In

sorghum plants, genes responsible for smut resistance were identified by

RAPD and RFLP markers (Oh et al., 1994). Marker-assisted recurrent selec

tion increases the frequency of genes of interest (GOI) when many genes are

involved in a specific trait expression. By using Marker-assisted recurrent

selection in drought conditions, genetic gain for higher grain yield up to 51

kg ha^–1 year^–1of maize was produced in the region of sub-Saharan Africa

(Beyene et al., 2016).

6.5.3 DEVELOPMENT OF TRANSGENICS

6.5.3.1 TRANSGENIC APPROACHES FOR BIOTIC STRESS

Biotic stress like bacteria, viruses, insect pests, etc. Many techniques have

been practiced, but not too many satisfactory results are shown, but these

stresses are possible due to the transgenic approaches. In subsections, we

have put in a nutshell the recent success story of the crop with biotic stress

resistance and tolerance with the help of novel transgenic techniques.