Water deficit induced physiological and amino acid responses in some rice varieties using NMR-metabolic analysis

Deficit irrigation (DI) is a choice made by producers to improve water productivity and might be highly preferred in future production programs in arid regions. Identifying DI-tolerant cultivars will be critical to improve rice (Oryza sativa L.) productivity under the future climate change conditions. Nuclear magnetic resonance (NMR)-based metabolomics is a recent technique that has received less attention so far and can be used to compare genetic differences in DI tolerance. For this purpose, field experiments were carried out during two successive summer seasons in Egypt to compare genetic differences for water deficit tolerance in seven rice genotypes using NMR technique. The genotypes Azucena and IRAT 170 achieved the best values of water productivity (WP) under DI, recording 1.79 and 0.99 kg m(-3) respectively, confirming their suitability in the water deficit breeding program to produce new promising lines and to keep yield potential stable under climate change conditions. The PLS-DA of 1H-NMR spectra showed a clear separation between genotypes under both full irrigation (FI) and DI conditions. Quantitative analysis showed that sucrose, threonine, glutamate, and allantoin were accumulated at DI when compared to FI conditions, and these metabolite compounds may be closely related to DI conditions. Tryptophan, as an aromatic amino acid, has increased across cultivars, most dramatically in Azucena and IRAT 170. Tyrosine and phenylalanine also increased in Azucena and IRAT 170, but not as dramatically as tryptophan. The rice genotypes Azucena and IRAT 170 could be successfully recommended for higher yields and quality under DI conditions.