K Mostafa, Bahram Abedy, K Hossein, Hossein Nemati, Hossein Aroiee
This research was carried out to investigate the tolerance of two imported spinach varieties (Spinacia oleracea L.) [Dutch F1 (Narita) and Italian standard (Viroflay)] and one native variety (Khardar Mashhad) to drought stress. A factorial experiment based on a completely randomised design (CRD) with 4 irrigation levels based on field capacity (FC) [100 % (no stress), 75 % (mild stress), 50 % (moderate stress) and 25 % (severe stress)] and 4 replications was conducted in Mashhad, northeastern Iran, during 2022. The results showed that drought stress significantly reduced growth and leaf-related traits, whereas proline accumulation increased markedly under severe drought stress and reached 1.01 µmol g-1 fresh weight (FW). Dutch F1 cultivar exhibited superior root traits, including higher root dry weight (DW) (1.63 g), root volume (14.68 cm³), root area (63300.75 mm²) and mean root diameter (0.51 mm), under drought stress, indicating enhanced drought tolerance compared with the other cultivars. In contrast, Khardar Mashhad showed the lowest root area (3842.25 mm²) and root length (7392.50 mm) under severe drought stress, indicating greater sensitivity to water deficit conditions. Chlorophyll A (Chl A) and total chlorophyll contents were highest in Viroflay (9.16 and 12.67 mg 100 g-1 FW, respectively). Under severe stress conditions, shoot fresh weight, shoot DW, leaf area and plant height decreased to 2.86 g, 0.54 g, 48.00 cm² and 11.37 cm respectively. Overall, Dutch F1 can be recommended for cultivation in northeastern Iran, because it had better root growth and development than the others by maintaining leaf water status, which caused more resistance to drought.