**1. Introduction**

With the ever-increasing world population (expected to reach 10 billion by 2050) [1, 2] and the changes in human dietary structure, global food demand is projected to keep increasing. All cereals combined, account for approximately 56% and 50% of global energy and protein needs, respectively, making them a major source of calories and protein for the human populace directly through human consumption and indirectly via consumption of cereal fed animals and animal products [3, 4]. The term "cereals" refers to members of the *Graminae* family which are cultivated for their edible seeds [3, 5]. The group consists of nine crop species: wheat (*Triticum*), rye (*Secale*), barley (*Hordeum*), oat (*Avena*), rice (*Oryza*), millet (*Pennisetum*), corn (*Zea*), sorghum (*Sorghum*) and triticale a hybrid of wheat and rye [3]. A variety of cereals are produced worldwide in different climates and

production systems ranging from the tropics to the temperate regions. The five major cereals on the global scale, in-terms of area under production and yield are; maize (*Zea mays*), rice (*Oryza sativa*), wheat (*Triticum aestivum*), barley (*Hordeum vulgare*), and sorghum (*Sorghum bicolor*) [4, 6]. Combined, these five crops contributes to about 50% of world food [7].

Although huge strides have been made in agricultural research and development (R and D) to increase crop productivity and efficiency of food production systems, global food deficits are still in existence [6]. In 2019, approximately 690 million were reportedly food-insecure with most of the affected people found in African and Asian countries [8]. Given the importance of cereals in the human diet, increasing their production will significantly improve current and future global food and nutrition security. To meet the projected high demand for food, food production should at least double by 2050 [8]. In particular, cereal production need to be increased by 60 to 110% by 2050 to meetup with the expected high demand for human consumption, livestock feed and industrial purposes needs [2].

Although cereals are notably important in global food and nutrition security, productivity of these crops is continually being hampered by biotic (e.g., pests and diseases) and abiotic (particularly; heat and drought) stresses [9]. These reduce crop yield and quality in field and post-harvest during storage [10]. The magnitude of the impact of these constraints on cereal productivity and yield quality however depends on crop species and variety, the extent and length of the stress on the crop, and the developmental stage at which the stress occur [11, 12]. If comparisons are made, global crop losses due to abiotic stresses are higher than those caused by biotic stresses [13].

If current and future food and nutrition security is to be guaranteed, cereal productivity should be increased to match food, feed and industrial demand [14]. This is done by increasing the efficiency of the cereal production systems, reducing the impact of biotic and abiotic stresses on cereals and policy changes. In addition, genetic crop improvement using both, the conventional and molecular breeding technologies, is also widely known as an important adaptation strategy for crops under the future predicted socio-climatic scenarios.
