Evaluation of Salt-Tolerant Guar (Cyamopsis tetragonoloba L.) Genotypes Based on Physiological, Biochemical, and Yield-Related Traits

Abstract

The 15 guar genotypes were exposed to different concentrations of salt (0, 10, and 15 dS m⁻¹ NaCl) in a factorial experiment (RCBD, r = 3) and different morpho-physiological, physiological, growth, and yield characteristics were assessed. The lowest seed gum (21.11%), carbohydrate (23.59%), protein content (24.20%), fat (2.21%), fiber (9.38%), digestible dry matter (37.90%), and yield (3865.50 kg/ha) were measured in plants treated with 15 dS/m salt; also, the highest ash content (5.08%), proline (82.88 μg/g FW), flavonoids (0.35%), phenols (2.37%), tannins (3.27%), and antioxidant enzyme activities (SOD 104.28, CAT 30.92, APX 74.80, and POD 40.20 units/mg protein) were observed in plants treated with 15 dS/m salt. Yield-related traits also differed significantly among genotypes (p ≤ 0.05). The highest plant yield (8124.31 kg) was gained from RGC-986 genotype under control conditions (0 dS/m). Furthermore, RGC-986 demonstrated the highest 1000-seed weight (48.22 g), number of seeds per plant (395.6), and overall average plant yield of 6458.9 kg/ha under three salinity levels, indicating strong genetic potential for commercial cultivation. S6673 and S6260 followed with plant yields of 5632.7 kg/ha and 5829.2 kg/ha, respectively. Pishen recorded the lowest values for all yield-related parameters, including 1000-seed weight (32.22 g), seeds per plant (152.7), and yield (4565.8 kg/ha). In terms of seed quality, the genotypes RGC-986, S-5885, S-6581, Saravan, and RGC-1031 demonstrated better resilience to salt stress, maintaining seed quality traits, while genotypes BR-99, S-6560, and Grembite were more sensitive, exhibiting marked declines across these parameters. Overall, the RGC-986 genotype was the Top-Performing Genotype (excellence) with high biochemical performance, lowest tannin, and yield superiority. The PCA confirmed the results of the Duncan test and highlighted the superiority of RGC-986 as an elite genotype under experimental conditions.