DREB Gene Expression of Introduced Wheat Genotypes in Response to Last Irrigation Cutoff

Abstract

Wheat (Triticum aestivum L.) is considered one of the most important crops global in terms of harvested area, and the second food crop after rice in importance. It is a source of daily protein by about 20% as well as a source of important calories. Recently, the level of wheat production does not have the perfect with an increasing world population potential of about a billion in 2050. Also, demands for wheat are expected to magnify up to 60%, in this case, the yield of wheat should increase from 1% to 1.6%. To achieve this, two strategies may be adopted, the first is producing more tolerant genotypes for biotic and abiotic stresses, while the second is enhancing the input use efficiency (GCARD, 2012; Narayanan, 2018). The global production of the wheat crop for the year 2019-2020 did estimate at 761.9 million tons according to FAOstat (2019), and the topmost countries in wheat production for the year 2017 were China, India, Russian, USA, France, Australia, Canada, Pakistan, Ukraine and Germany. In Iraq, there is an increase in cultivated area and production for the winter season of the year 2020. Wheat productivity was estimated at 6238 thousand tons by an increase of 43.6% over last year production, which estimated 4343 thousand ton (Agricultural Statistics Directorate, 2020). Climate changes, that Iraq exposes to a reduction of the rain and retention and increased of temperatures thus lands have deteriorated due to droughts such as desertification and the exhaustion in natural resources of the land (Saad, 2016); This makes Iraq face great challenges in terms of providing food, chief among them is the reduction of water from their sources, also its location within areas characterized by low rainfall. Which affects directly on grains and the most important is the wheat. Wheat grains contains 12-17% protein, 76-78 % starch, and oil 1.2-1.5% (Hadi et al., 2013; Rijib and Jbara, 2016). During exposure to abiotic stresses, The plants show a wide 2 range of morphological, physiological, and biochemical alternations. The molecular changes of genes organize at dehydration and cold conditions and confer tolerance thus keep the plant alive. Stress-responsive gene expression timing is regulate through a set of transcription factors and Cis-acting elements in stress-inducible promoters. This makes the stress-responsive transcription factors (TFs) genes an important target in genetic engineering programs to enhance tolerance to abiotic stress, where their overexpression reflects positively or negatively on the expression of genes that they control (Yamaguchi Shinozaki and Shinozaki, 2006; Akhtar et al., 2012). DREBs (dehydration responsive element binding) are important plant transcription factors (TFs) that belong to APETALA2 (AP2) family transcription factors. DREBs regulate the expression of many genes that induce stress tolerance at most an ABA-independent way. Also, they have a crucial function in improving tolerance for abiotic stress via the interaction with DRE/CRT cis-element that exist at the promoter zone of different responsive gene responsible for abiotic stress. Recently, DREB1/CBF genes are one of the genes used in genetic modification engineering programs to serving in producing more tolerant crop plants (Lata and Prasad, 2011; Akhtar et al., 2012). Drought is one of the most critical environmental stresses which affect all plant functions. With drought stress occurs, it leads to produce abscisic acid (ABA), which plays a vital function in tolerating drought besides induced most of the drought stress-inducible genes (Shinozaki and Yamaguchi-Shinozaki, 1997). CRT/DRE elements participate in ABA signal transduction; besides that its existence is required for the ABA responder element in the cor78a / rd29A promoter (Yamaguchi-Shinozaki and Shinozaki, 1994). Revealed later that the DREBs are ABA-independent, excepting CBF4, which is ABA-responsive, and includes CRT/DRE components in the ABA- 3 dependent pathway. The DRE participation in ABA-dependent organizing for stress response refers to more interaction between the ABA-dependent and ABA-independent signal transduction pathways (Agarwal et al., 2006). This study aims to estimate DREB gene expression of some introduced genotypes of wheat and cultivation under the influence of water stress in order to continue using the superior genotypes in the western parts of Iraq.