Spatio-temporal evaluation of drought adaptation in wheat revealed NDVI and MTSI as powerful tools for selecting tolerant genotypes

Context Water is one of the major limiting factors for wheat production. Mult-environmental evaluation is necessary to identify stable drought tolerant wheat genotypes. Objectives To identify stable drought tolerant wheat genotypes and reliable phenotypic and/or spectral markers for drought tolerance. Methods One hundred ninety-six diverse wheat genotypes were evaluated at three different locations in India for two years (E1 to E12). Drought was imposed at the heading stage (Z59) by withholding irrigation until the moisture content reached <45% as compared to the control (100%). Various Morpho-physiological and phenological traits: Days to flowering (DTF) and maturity (DTM), plant height (PH), grain yield (GY), NDVI, canopy temperature depression (CTD), and chlorophyll readings were recorded. Different stress indices and stability models (AMMI - Additive Main Effects and Multiplicative Interaction; WAASB - Weighted Average of Absolute Scores from the singular value decomposition of the matrix of BLUPs; and MTSI - Multi-Trait Stability Index) were used to identify the stable and tolerant genotypes. In addition, discriminate function analysis (DFA) was performed to identify drought tolerant genotypes. Results Genotype performance reduced significantly under drought for all traits in all environments. Overall, GY was reduced by 35% under drought compared to control. Pooled ANOVA showed that 81% of the variation in grain yield was due to the environment and 10.6% due to its interaction with genotypes. MTSI and WAASBY identified 11 common genotypes with stable performance across all environments. Further, 29 stable genotypes selected by MTSI (with 15% selection intensity) had higher selection differential than other stability models. Further, NDVI at maturity showed a positive and significant correlation [r = 0.41** in E2 and 0.36** in E4) with the GY specifically under drought for two years. Conclusion MTSI is an effective method for selecting stable wheat genotypes under drought conditions. NDVI may be a high throughput screening tool for drought tolerance. Implications MTSI may be used to identify stable genotypes, while DFA is useful in selecting drought tolerant genotypes. Further, NDVI can be used in addition to yield traits to screen wheat genotypes for drought tolerance.