Genetic insight into physiological and spectral reflectance indices of synthetic wheat germplasm in various phenological stages under salinity stress

Spectral reflectance indices (SRIs) are increasingly recognized as valuable tools in wheat breeding programs for assessing traits that typically require destructive measurements. Little is known about the application of non-descriptive methods in synthetic wheat and the effect of phenological stage. This study assessed variation and genetic parameters of SRIs and physiological parameters in a panel of synthetic wheat under both control and salinity conditions as well as the efficacy of SIR indices for selection across different phenological stages. Results indicated that salinity stress significantly reduced grain yield and relative water content while increasing ascorbate peroxidase (APX) enzyme activity across all growth stages. APX, peroxidase (POD), and the Green Difference Vegetation Index (GDVI) showed the highest heritability and genotypic coefficient of variation (GCV) across all phenological stages, suggesting strong genetic control over these indices. The Normalized Difference Vegetative Index (RNDVI) also demonstrated a similar trend under control conditions across all phenological stages. Principal Component Analysis (PCA) indicated that assessing SRIs concerning grain yield and physiological parameters was more effective during the anthesis and maturity stages than at milking. However, PCA effectively identified high-yielding and salt-tolerant genotypes during the milking stage, particularly at maturity. Overall, the SRIs analysis in wheat genotypes highlights their potential for optimizing selection timing and improving precision in breeding programs.