Introduction

One-sixth of the world's human population has insufficient food to sustain life, and food supply will need to double by 2050 to meet this demand. Agricultural genetics is one of the components of the solution to meet this challenge (Nature Genetics, 2009). The most serious challenges economies and societies will face over the next decades include providing food and the water needed for food production, to a world that will see its population increase by a third in the face of mounting environmental stresses, worsened by the consequences of global climate change.

The challenge of increasing food production in the face of climate change will be greatest for the production of the staple grain crops that form the basis of diets the world over. Wheat, maize and rice are the three major staples, covering together 40% of the global crop land of 1.4 billion ha (FAOSTAT, 2009). Together they provide 37% of all protein, and 44% of all calories for human consumption (Table 7.1). Each crop provides more than 50% of the daily caloric uptake in regions with high consumption, for example North Africa and Central Asia for wheat, sub-Saharan African countries and mesoamerican countries for maize, and South and Eastern Asian countries for rice, and especially among the poorest people in these regions. Wheat is, with 220 million ha, the most widely grown crop followed by maize with 158 million ha and rice with 155

© CAB International 2010. Climate Change and Crop Production (ed. M.P. Reynolds)

Table 7.1. Percentage of calories and protein in the human diet obtained from wheat, maize and rice globally and in the developing world (FAOSTAT, 2009).

Grain crop Region Calories (%) Protein (%)

Table 7.1. Percentage of calories and protein in the human diet obtained from wheat, maize and rice globally and in the developing world (FAOSTAT, 2009).

Grain crop Region Calories (%) Protein (%)

Maize

World

5

4

Developing countries

6

5

Wheat

World

19

20

Developing countries

17

19

Rice

World

20

13

Developing countries

25

18

Total from wheat,

World

44

37

rice and maize

Developing countries

48

42

million ha. Average yield of maize, rice and wheat is 5, 3.9 and 3 t/ha, respectively. Although around 135 countries produce more than 10,000 t of maize compared with 100 countries that produce more than 10,000 t of wheat, wheat shows the widest geographical distribution because it is grown from Ecuador to 67°N in Scandinavia to 45°S in Argentina, Chile and New Zealand (Trethowan et al., 2005). Maize is grown from 55°N in Western Europe to 45°S in New Zealand. Rice is grown in a narrower geographic belt between 40°N in Japan and 30°S in Brazil, but is grown over a very wide range of hydrological environments within this area.

Plant breeding, using the combined potential of conventional, molecular and genetically modified technologies, will provide cultivars with greatly enhanced nutrient and water-use efficiency, enhanced tolerance to heat and drought, resistance to diseases and appropriate end-use and nutritional quality and, possibly most important, increased ability to cope with the increasing extremes in temperature and precipitation across regions and over years. The wide range of environments in which wheat, rice and maize are now grown indicates that the genetic variability exists within these species to cope with the large and rapid climate shifts we are facing, but more integrated and collaborative approaches to crop variety evaluation and the exchange of seed and information will be required to avoid rapid declines in production in severely affected regions. In this chapter, we intend to survey the methods by which breeding programmes cope with environmental variability, and consider how these methods may be applied to the problem of coping with rapid climate change in crop production systems. The chapter describes how multi-location testing, as well as managed stress screening and improved information flow to national and regional breeding programmes, can help buffer important crop production systems against the disruptions likely to arise from global climate change. The emphasis will be on wheat, with supporting information from maize and rice. Other chapters in this book address specific aspects of genetic improvement, including breeding for disease resistance (Legreve and Duveiller, Chapter 4), adaptation to heat and drought stress (Reynolds et al., Chapter 5), adaptation to salinity, waterlogging and inundation (Mullan and Barrett-Lennard, Chapter 6), and genetic approaches to reduce greenhouse gas emissions associated with crop production (Parry and Hawkesford, Chapter 8).

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