**3. Major current and emerging constraints to cereal production**

The historical and current importance of cereals in the human diet clearly shows that global food supply and human nutrition are anchored on cereal production [2]. Major constraints to global cereal production can be broadly grouped into biotic and abiotic factors [9]. These are continually reducing potential yield and crop quality during production and post-harvest despite efforts to increase food supply to meet demand [10]. The magnitude of the impact of these constraints on cereal productivity and yield quality depend on the crop species and variety, the extent and length of the stress factor on the crop, and the developmental stage at-which the stress affects the crop [11, 12]. If comparisons are made, crop losses due to abiotic stresses are higher than losses effected biotic stresses [13]. A lot of scientific studies have been done to understand the physiological and molecular response of plants to different biotic and abiotic stresses that limit grain yield production yet huge yield gaps still exist between optimal and stressful conditions. More studies are therefore paramount if future food and nutrition security is to be guaranteed.
