The Importance Of Wheat In Agriculture

Chapter 1 INTRODUCTION

Wheat, (Triticum aestivum L. em Thell.) a crop with ‘golden grain’ and is a dominant crop of world commerce. It feeds one fifth of human population with global annual production of 676 million tonnes (FAOSTAT 2012). Wheat is grown on more than 240 million ha, larger than for any other crop, and world trade is greater than for all other crops combined. Wheat is foremost important and strategic cereal crop for the world’s populations. It is the major staple food of about two billion people (36% of the world population). It exceeds in acreage and production every other grain crop (including rice, maize, etc.) and is therefore, the most important cereal grain crop of the world, which is cultivated over a

More than 50% of the area under wheat cultivation is affected by periodic drought (Rajaram, 2001; Pfeiffer et al., 2005) and it has become one of the main environmental threats to grain production especially the arid and semiarid regions of the world and ultimately to global food security (Chaves et al., 2003). In major wheat-growing areas of the world, particularly with a Mediterranean climate, mean pan evaporation often surpasses average precipitation especially during grain filling, leading to drought during reproductive and grain-filling phases, which is also known as ‘terminal drought’ (Reynolds et al., 2005a). It comes in to play with heat stress. Exposure to higher than optimum temperature reduces yield and decreases the quality of wheat ( Fokar et al., 1998;Maestri et al., 2002;Wardlaw et al., 2002). Amongst all phenological stages in wheat reproductive and grain filling stages are most sensitive ( Pradhan et al., 2012) and results in substantial yield losses. The severity and duration of this drought stress determine the extent of the yield losses. The principal reasons for these losses are reduced rates of net photosynthesis owing to metabolic limitations, oxidative damage to chloroplasts, stomatal closure,