Thermal imaging and multivariate techniques for characterizing and screening wheat genotypes under water stress condition

•Thermal imaging and multivariate techniques were used to characterise water stress.•A Novel stress index - Normalized Water Stress Tolerance Index (NWSTI) was developed.•NWSTI was validated against CWSI, IG and CSI3 for water stress characterization.•NWSTI was used to screen wheat genotypes for water stress tolerance. The present study was undertaken to understand the combined impact of thermal imaging and multivariate techniques to characterize and screen different wheat genotypes under water stress condition. Ten wheat genotypes namely HD-2987, HDR-77, PBW-343, PBW-175, HD-2967, HD-2781, HD-2985, HD-3043, C-306 and PBW-502 were grown under two irrigation conditions (I and Io corresponding to IW/CPE ratio of 1.0 and 0.4, respectively). The water stress conditions in wheat genotypes were characterized thermo-graphically using canopy temperature-based stress indices, namely crop water stress index (CWSI), stomatal conductance index (IG) and stomatal resistance index (CSI3). Simultaneously, plant biophysical parameters like normalised difference vegetation index (NDVI), leaf area index (LAI), transpiration, stomatal conductance, photosynthesis, were measured at peak vegetative stage along with yield and its attributes (panicle number, tiller number, 1000 seed weight, crop yield, total dry matter, harvest index) were observed. These parameters were analyzed using multivariate techniques namely principal component analysis (PCA), hierarchical cluster analysis (HCA) and discriminant analysis (DA) to develop a new index called normalized water stress tolerance index (NWSTI), to group wheat genotypes depending on their ability to tolerate water stress. Based on these multivariate analysis, wheat genotypes were classified as tolerant (C-306, HD-3043, HD-3987 HD-3985 and HD-2781), moderately tolerant (HDR-77, PBW-175 and PBW-502) and sensitive (HD-2967, PBW-343) to water stress with NWSTI score of >0.66, 0.33–0.66 and