Drought-induced variations in nutritional composition of grain and bran of contrasting rice genotypes

Drought is a key environmental element that affects rice (Oryza sativa L.) productivity and quality. Control and drought-treated rice grain (milled) and bran fractions of two contrasting rice genotypes (N22-drought-tolerant and IR64-drought-sensitive) were evaluated based on proximate composition, vitamins, minerals, and nutritional quality indices. Except for carbohydrates and amylose content, bran from both genotypes had higher concentrations of all parameters (proximate, minerals, vitamins, phenols, amino acids, and phytic acid) analyzed in this study. Protein level ranged from 9–11% in grain to 13–15% in bran. Macronutrients (Na, Ca, K, Mg, P) increased after drought in both genotypes. Under drought, thiamine level ranged from 0.07 to 1.97 mg/100 g, riboflavin level from 0.02 to 0.43 mg/100 g, and α-tocopherol from 1.67 to 8.34 mg/100 g in both fractions. N22 showed higher amylose (20.44% and 4.84%) and phenol (0.46 mg/GAE and 2.54 mg/GAE) content in both grain and bran fractions under drought condition. Proline accumulated at higher concentration (2.732 g/100 g) than other amino acids in N22 under drought. Phytic acid ranged from 0.213 to 2.752 g/100 g in drought. To the best of our knowledge, this is the first preliminary report on nutritional quality analysis of rice grain and bran under drought stress. The current findings may help breeders in development of high-quality, drought-tolerant rice varieties, and will also provide a strong foundation for utilizing bran as an essential food ingredient to improve human nutrition and may help breeders to use this tolerant genotype as better parents in further crossings.