**2. Effect of drought stress on sugarcane production**

Sugarcane, the world's major industrial C4 crop mainly grows in the tropic/ subtropic regions and used for sugar and bioenergy. In India, the tropical regions (Maharashtra, Andhra Pradesh, Tamil Nadu, Karnataka, Gujarat, Madhya Pradesh, Goa, Pondicherry and Kerala) shared about 45% and 55% and the Sub-tropical region (Uttar Pradesh, Bihar, Haryana and Punjab) accounted for about 55% and 45% of the total sugarcane area and production in the country, respectively. Prevailing climatic factors particularly atmospheric CO2, temperature, precipitation are the key factors for sugarcane production worldwide. Among these, the availability of water in addition to atmospheric CO2 is considered to have been a major driving force for the evolution and the ecological success of C4 plants [8, 9]. Drought or prolonged dry periods are limiting crop yields in tropical worldwide areas, including sugarcane production by 40–60% [10, 11]. Sugarcane is a globally important crop for food and industrial input production, accounts for 60% of world sugar output as well as bio-ethanol and energy generation [12]. Sugarcane is also known as water guzzler consumes about 22.5 million liters of water per hectare during its long growing cycle. In tropical India, the total water requirement of the crop for optimum growth varies from 2000 to 3000 mm inclusive of rainfall, while in Sub-tropical India, the water requirement is 1400–1800 mm. Drought severely depresses cane yield to the tune of 40–60%, whereas, the sucrose formation and sucrose recovery are reduced up to 5%.
