Triticeae Genomics and Genetics, 2024, Vol.15, No.5, 266-276 http://cropscipublisher.com/index.php/tgg 269 3.2 The history of genetic improvement One of the most critical traits selected during the domestication of barley was the development of non-shattering spikes, which allowed for more efficient harvesting by preventing the mature grains from dispersing naturally (Fuller, 2007; Pourkheirandish et al., 2015). This trait evolved through mutations in specific genes that controlled the brittleness of the rachis, the part of the plant that holds the grains. In wild barley, the rachis is brittle, causing the grains to shatter and disperse, while in domesticated barley, mutations led to a tough, non-brittle rachis that retained the grains on the plant (Pourkheirandish et al., 2015). These genetic changes were crucial for the transition from wild to cultivated barley, as they enabled early farmers to harvest and store the grains more effectively. The genetic improvement of barley also included the development of six-rowed barley from the ancestral two-rowed form. This change, controlled by a specific gene, resulted in a significant increase in the number of seeds per spike, thereby enhancing the crop's yield (Pourkheirandish and Komatsuda, 2007). The identification and study of these domestication genes have provided valuable insights into the mechanisms by which wild barley was transformed into a staple food crop. The evolution of these traits was not uniform across all regions; instead, it occurred through multiple independent events, reflecting the diverse selection pressures and cultivation practices of early agricultural societies (Pourkheirandish et al., 2015). 3.3 The role of barley in early agriculture Barley played a pivotal role in the development of early agricultural societies in the Near East and beyond. As one of the founder crops of Neolithic agriculture, barley was integral to the transition from hunter-gatherer lifestyles to settled farming communities (Piperno et al., 2004; Mascher et al., 2016). The crop's adaptability to different environmental conditions and its relatively short growing season made it a reliable food source for early farmers. Archaeobotanical evidence from various sites in the Fertile Crescent and surrounding regions indicates that barley was widely cultivated and used in diverse ways, including as a staple food and for brewing beer (Piperno et al., 2004; Leipe et al., 2017). The spread of barley cultivation from its center of origin in the Fertile Crescent to other parts of the world was facilitated by its versatility and the development of different barley phenotypes suited to various climates and agricultural practices. For instance, the Okhotsk culture in northern Japan utilized barley as part of a mixed subsistence strategy that included hunting, fishing, and gathering, highlighting the crop's importance in diverse cultural contexts (Leipe et al., 2017). The historical significance of barley is further underscored by its role in the diets and economies of ancient civilizations, where it was used not only for food but also for brewing, which became a central aspect of many cultures (Piperno et al., 2004). In summary, the domestication and genetic improvement of barley were crucial developments in the history of agriculture, enabling the crop to become a staple food source for early human societies. The selection of key traits such as non-shattering spikes and the evolution of six-rowed barley significantly enhanced the crop's utility and productivity, facilitating its widespread adoption and cultivation across different regions and cultures. 4 Varietal Selection and Brewing Traits of Malting Barley 4.1 Major malting barley varieties Barley varieties are primarily categorized into two-row and six-row types, each with distinct applications in beer brewing. Two-row barley is predominantly used in large-scale beer production due to its higher starch content and lower protein levels, which contribute to a cleaner and more efficient fermentation process (Figure 2) (Kim et al., 2013; Doe, 2019). In contrast, six-row barley, which is more commonly used in smaller-scale brewing operations such as microbreweries, has a higher protein content that can enhance the body and foam stability of the beer but may also introduce more haze and off-flavors if not managed properly (Kim et al., 2013; Kim et al., 2014). The choice between two-row and six-row barley often depends on the desired characteristics of the final product and the specific brewing techniques employed.
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