Biotechnological applications to improve salinity stress in wheat
1.1 Introduction For food, humans rely on approximately 275 crops (Tilman et al., 2011). Out of these, three crops, wheat, maize and rice, are significant cereal crops that contribute to major dietary requirements as staple foods for humans – a reason why they are collectively termed the ‘big three cereal crops’ (Shewry, 2009). Comparatively, wheat is the most important cereal crop that contributes a major portion of the daily diet for humans (Slade et al., 2012). It is estimated that wheat is a source for one‐fifth of total calories utilized by humans globally (Waines & Ehdaie, 2007). Wheat grains contain vital constituents such as carbohydrates, including 60–70% starch (Slade et al., 2012) and 8–15% protein such as glutenin (Shewry et al., 1995) and gliadin (D’Ovidio & Masci, 2004). From the total wheat grain produced globally, 65% is utilized as food by humans while the remaining 35% is distributed among livestock feed (21%), seed material (8%) and raw material (6%) in industries such as the production of vitamins and antibiotics, manufacturing of paper; it is also used as a fermentation substrate or as adhesives in various products (Shewry & Jones, 2005). 1.1.1 History of wheat: from domestication to revolutions In ancient times, wheat was a product of the activities of hunter‐gatherers but about 10,000 years ago, the Neolithic Revolution laid the basis for domestication of various crops (Waines & Ehdaie, 2007). This domestication process focused mainly upon cereal crops, and wheat is considered the originator of domesticated crops (Peleg et al., 2011). With the passing of time, problems arising in the domestication process compelled scientists to analyse and study various concerns such as local conditions, yield maximization, development of improved cultivars and storage techniques (Cavanagh et al., 2013). Eventually, these findings resulted in major events such as the Agricultural Revolution in the 19th century (Godfray et al., 2010) and the Green Revolution in the 20th century (Waines & Ehdaie, 2007). Wheat domestication followed by major revolutions and scientific achievements contributed to speciation and initiation of new varieties (Shewry, 2009). The factors involved in such speciation primarily include adaptations to the ecology of an area as soon as wild‐ type wheat cultivars were moved for domestication purposes (Chaudhary, 2013). These adaptations under the influence of epigenetics offered the opportunity to select the desired traits in wheat such as yield, grain quality, grain size and many other phenotypic attributes (Burger et al., 2008). Thus, wheat evolved into many varieties in response to human cultivation practices, selection procedures and the phenomena of epigenetics (Fuller, 2007). Since the Green Revolution, technologies have been incorporated into crop improvement practices, specifically wheat, in various ways (Schmidhuber & Tubiello, 2007). These include successful development of hybrids with enhanced desired traits, development of pathogen‐resistant plants, enhanced yield, improved nutrient contents, affordable fertilizer requirements and improved irrigation systems (Godfray et al., 2010). Biotechnological applications to improve salinity stress in wheat Sami ullah Jan1 , Ghulam Kubra1 , Mehreen Naz2 , Ifrah Shafqat2 , Muhammad Asif Shahzad1 , Fakiha Afzal1 and Alvina Gul Kazi1 1Atta‐ur‐Rahman School of Applied Biosciences (ASAB), National University of Sciences and Technology (NUST), Islamabad, Pakistan 2Department of Bioinformatics and Biotechnology, International Islamic University, Islamabad, Pakistan Chapter 1 0002580878.indd 1 10/3/2015 6:20:16 PM COPYRIGHTED MATERIAL 2 Chapter 1 The consequences of all aspects of the Green Revolution increased yield to fulfil the world’s food requirements (Tilman et al., 2011). Citește mai departe, download
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