**1. Introduction**

Wheat (*Triticum aestivum*) is known as one of the most important cereal crops and is extensively grown worldwide [1]. Wheat contributes to 50% and 30% of the global grain trade and production respectively [2]. Wheat is also known as a staple food in more than 40 countries of the world. Wheat provides 82% of basic calories and 85% of proteins to the world population [3, 4]. Wheat-based food is rich in fiber contents than meat-based food. Dough produced from bread wheat flour has different viscoelastic properties than other cereals. It is considered a higher fiber food. Therefore, its positive effects on controlling cholesterol, glucose, and intestinal functions in the body were observed [5]. Primarily, wheat is being used to make *Chapatti* (Bread) but it also contributes to other bakery products. Wheat utility and high nutritional value made it the staple food for more than 1/3rd population of the world. Wheat grain is separated from the chaff and stalks after the harvesting of wheat. Stalks of wheat are further used in animal bedding and construction material. Globally, the need for wheat production is enhancing even in countries having unfavorable climates for its production. Global climate changes are badly affecting the production of wheat and it raised the concern for food security.

It is estimated that annual cereal production should be increased by 1 billion tons to feed the expected population of 9.1 billion by 2050 [1]. The current scenario demands an increase in crop productivity to meet the increased requirements of food supply [6]. Wheat is grown in tropical and subtropical regions which experiences a lot of stress. These stresses result in a reduction of yield [7]. Major environmental stresses include cold, salinity, heat, and drought which are drastically affecting its yield. However, water and heat are considered as the key environmental stresses which caused in reduction of the wheat yield globally [8, 9]. So, genetic improvements related to yield and stress tolerance are mandatory to enhance the production of wheat [10, 11].

#### **2. Genetically modified wheat plants**

Genetically modified wheat plants have been produced by the use of bacteria. Wheat plants were inoculated with the plant-growth-promoting bacteria (PGPB) which resulted in the higher expression of abiotic stress (mainly drought and salinity) tolerant genes [12]. PGPB inoculated wheat cultivars also showed the higher expression of genes encoding antioxidant-enzymes, such as *catalase* (CAT),


#### **Table 1.**

*Development of transgenic wheat having various traits/phenotypes.*

*peroxidase*, *ascorbate peroxidase* (APX), and *glutathione peroxidase* (GPX). So, it was concluded that PGPB used in wheat plants resulted in increased tolerance to abiotic stresses [12]. Cold shock proteins increase the survival of bacteria in severe environmental conditions. *CspA* and *CspB* genes from bacteria were transformed into wheat. Transgenic wheat plants expressing *SeCspA* and *SeCspB* were observed to have decreased water loss rate, increased proline and chlorophyll contents under salinity, and less water-stress conditions [13]. It was further investigated that *SeCsp* transgenic wheat plants resulted in enhanced weight and yield of grain than the control plants. *SeCspA* transgenic wheat plants were observed to have an improved water-stress tolerance than the control plants (**Table 1**, [13]).

Gluten is a protein comprised of gliadins found in wheat. Gluten is the main cause of coeliac disease in individuals. Bread-making quality of wheat is determined by the gluten proteins. Wheat varieties with less gliadin contents were produced using gene-editing technologies and RNAi (RNA interference). Wheat lines lacking immunogenic gluten were produced. Low immunogenic gluten and more nutritional values were added in one wheat line named E82. A better microbiota profile (protection microorganisms available in the gut) was observed in the NCWS patients using the bread made with E82 [28]. Plant cuticle has a positive role in the protection of plant against biotic and abiotic stresses. Wheat plants transformed with *TaSHN1* resulted in increased water-stress tolerance by reducing the leaf stomatal density and changing the composition of the cuticle [29].

#### **3. Biotic stress tolerance in wheat**

Wheat is considered an excessive contributor toward the human calorie intake [30]. Pests and pathogens cause yield losses in wheat up to 21.5% of the total losses and could be reached to 28.1% [31]. Wheat is affected by the fungal disease, powdery mildew caused by *Blumeria graminis* f. sp. tritici (Bgt). Powdery mildew is a damaging disease that resulted in greater loss of wheat [32]. Broad-spectrum resistant genes (BSR) are considered to have the most significant role to control powdery

#### *Introductory Chapter: Current Trends in Wheat Research DOI: http://dx.doi.org/10.5772/intechopen.103763*

mildew. *CMPG1-V* gene was cloned from the *Hynaldia villosa* and it was observed that higher expression of *CMPG1-V* gene resulted in the Broad-spectrum resistance against powdery mildew [33, 34]. Barley *chi26* gene could also be used to enhance the resistance against powdery mildew and rust through genetic modification [35]. Some epigenetic regulators were determined to have a role in wheat powdery mildew resistance. *TaHDT701* is a histone deacetylase that was found as a negative regulator of wheat defense against powdery mildew. *TaHDT701* was observed to be associated with the one repeat protein (TaHOS15) and RPD3 type histone deacetylase TaHDA6. Knockdown of this histone deacetylase complex (*TaHDT701*, *TaHDA6*, *TaHOS15*) in wheat resulted in increased powdery mildew tolerance [36].

*Fusarium graminearum* is a plant fungal pathogen that causes a devastating disease called Fusarium head blight in wheat. It results in the reduction of wheat production. Genetic techniques were used to increase the FHB (Fusarium head blight) resistance in wheat. Transgenic wheat plants expressing barley class II chitinase gene 2 were observed to have a higher resistance against *Fusarium graminearum* [37]. *Lr10* and *Lr21* were cloned and transformed into wheat. The transgenic plants were reported to be resistant to leaf rust disease. Evolution and diversification of *HIPPs* (heavy metal-associated isoprenylated plant proteins) genes were studied in Triticeae [38]. *HIPPs* genes of *Hynaldia villosa* were cloned through homologybased cloning. Transgenic wheat having *HIPP1-V* was developed and the role of *HIPP1-V* in cadmium stress was characterized. It was observed that higher expression of this gene resulted in increased tolerance to cadmium stress. Therefore, *HIPP1-V* could be used to increase the tolerance in wheat against cadmium [39].
