**1. Introduction**

The major challenge of this century is to produce sufficient food to meet the ever-growing population (10 billion by 2050) despite reductions in quantity and quality of arable land,

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

water and increasingly variable weather patterns that are associated with climate change [1]. Abiotic stresses such as drought, salt, cold, and high temperature continue to affect the crops individually or in combination. Climate change has increased the intensity of heat stress that adversely affects both agricultural and horticultural crops resulting in serious economic losses, particularly in agricultural dependent countries. Global climate change risks are expected to be as high as global mean temperature increase of ≥4°C would pose large risks to global and regional food security [2]. The combination of high temperature and humidity would be compromising the current production of the major food crops such as wheat, rice, and maize in tropical and temperate regions. The climate change without adaptation is projected to negatively impact production for local temperature increases of ≥2°C above the late twentieth-century levels [2].

**Crops Threshold temp. (ͦC) Developmental stage**

33 Biomass

20–30 Vegetative 15 Reproductive 35 Postanthesis

25 Grain formation and yield 34 Grain yield and quality

Breeding Cultivars for Heat Stress Tolerance in Staple Food Crops

http://dx.doi.org/10.5772/intechopen.76480

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35 Protein accumulation

36–40 Pollen viability and fertilization

33–38 Photosynthesis 38 Vegetative

26–34 Vegetative 25–28 Reproductive

15–30 Growth

Common bean 23 Reproductive development

Soybean 26 Reproductive development

23 Post-anthesis 30.2 Pollen germination 36.1 Pollen tube growth

Pea 15–20 Vegetative growth

Groundnut 10–41 Germination

Lentil 32/20 Reproductive stage Cotton 31.8–43.3 Pollen germination

**Table 1.** Critical growth stages and threshold temperatures of important food crops.

25 Reproductive growth

29–33 Vegetative development 25–28 Vegetative growth 22–24 Reproductive growth

28.6–42.9 Pollen tube growth

Rice 15–35 Germination

Wheat 10–35 Germination

Maize 15–40 Germination

Sorghum 20–40 Germination

Pearl millet 10–34 Germination Chickpea 10–35 Germination

Extreme climates including very high temperatures are predicted to have a general negative effect on crop growth and development leading to catastrophic loss of crop productivity and also widespread famine in future [3]. The increase of temperature by 3–4°C is expected to reduce crop yields by 15–35% in Africa and Asia, whereas by 25–35% in the Middle East [4]. Hence, adopting the mitigation strategies such as reforestation, water harvesting in field and households, optimal use of CO2 emitting devices and reducing wetland crops to avoid methane emission, etc., are essential, but as they are dependent on government policies, it is difficult to achieve them in short term. For long term, the adoption of extinct native crops and its diversity in individual farm is highly required to meet not only the food and nutritional security but also the feed security for farm livestock. The development of heat stress tolerant cultivars would be an ideal solution for sustainable food production for which research is still in preliminary stage and needs donor investment to progress competitively to deliver climate-smart cultivars to farmers. A recent study has shown the climatic shift in >25% of its geographical area in India [5] and also significant increase of aridity in several parts of the country. Therefore, government needs to re-standardize the climate zones with respect to aridity and temperature while planning for any developmental and agricultural intervention.
