Response of Two Libyan Wheat Cultivars (Triticum turgidum L. and Triticum aestivum L.) to Cadmium Stress: Growth Parameters, Germination, and Seedling Vigor

Abstract

Cadmium (Cd) toxicity is a major abiotic stress that significantly impedes wheat productivity across the globe. This study was designed to evaluate the relative tolerance of two indigenous Libyan wheat cultivars, 57LW (durum wheat, Triticum turgidum L.) and 29LW (bread wheat, Triticum aestivum L.), obtained from the Agricultural Research Centre (ARC) in Tripoli. The experiment utilized a completely randomized design (CRD) to test the effects of four distinct concentrations of CdSO₄: 0, 100, 250, and 500 µM. Six critical seedling traits were monitored over a 14-day period: germination percentage, shoot length, root length, root fresh weight, root dry weight, and the seedling vigor index (SIV). The findings revealed that cadmium stress significantly affected most growth parameters, though cultivars exhibited distinct levels of resistance. At the highest concentration (500 µM), the germination percentage for 29LW dropped by 27%, whereas 57LW showed a more resilient reduction of only 14%. Furthermore, shoot length in bread wheat (29LW) decreased by 46.8% at 500 µM, while durum wheat (57LW) maintained statistically stable shoot lengths across all treatments. Root system metrics, including length and biomass, declined in both cultivars as Cd levels increased, yet bread wheat consistently showed higher susceptibility. Specifically, at 500 µM, 29LW suffered reductions of 65.4% in root length and 72.1% in root dry weight, compared to 39.0% and 60.4% in 57LW, respectively. The seedling vigor index (SIV) emerged as the most comprehensive indicator of stress impact, decreasing by 65.7% in 29LW and 31.7% in 57LW at the maximum dosage. Statistical analysis using Duncan’s test confirmed significant differences between the cultivars, particularly regarding root traits and overall vigor. These results demonstrate that the cultivar 57LW possesses superior cadmium tolerance mechanisms, making it an excellent candidate for cultivation in Cd-contaminated soils and for future breeding programs aimed at enhancing environmental stress resilience in Libya.