Effects of water shortage and drought on grain quality
Water is one of the most essential inputs for production of crops, and rice among all the cereals consumes the most water for irrigation. In many systems, production of 1-kg rice takes 5000 L of water although this can be reduced to about 2000 L (Lal 2007). The water status of the soil has a dramatic effect on yield, and it also affects grain quality (Dingkuhn and Le Gal 1996). Traditionally, rice is planted under submerged condition; however, nonflooded plastic film mulching (PM) and nonflooded wheat straw mulching (SM) are being considered new water-saving techniques in rice production. Different water management treatments, namely PM, water-saving irrigation, and conventional irrigation, significantly affected brown rice rate, head rice rate, chalky grain rate,
amylose content, and protein content in a cultivar and grain position dependent manner. Of all variables, water treatment had the strongest effect on protein content (Cheng et al. 2003b). SM was found to significantly increase milling quality and reduced the percentage of chalky grain, chalky size, and chalkiness, while PM showed opposite effects. Gel consistency was found decreased under PM (Zhang et al. 2008b). Rice is the only crop which can survive periods of submergence. However, flooding just before harvest brought visible changes to the physical appearance of grains. The kernels in flood-affected samples became soft and developed fissures which contributed to low head rice recoveries, and the milled rice had lower kernel weight and protein content, but showed higher amylose and ash content (Singh et al. 1990). Growing rice in an upland nonflooded environment
also affects grain quality. A recent study involved several cooking and nutrient quality traits, including amylose content, gel consistency, gelatinization temperature, and protein content, in the same populations grown under upland and lowland conditions. The phenotypic values of all four traits were significantly higher under upland environment
than lowland environment (Guo et al. 2007