Effect of cumin accession on seed germination and early vigor of Cuminum cyminum L. under temperature and salinity stress

Résumé

Cumin ( Cuminum cyminum L.) establishment in arid and semi-arid systems can be limited during germination by thermal and saline stress, yet accession-level variation remains poorly characterized. This study aimed to quantify germination and early-vigor responses of nine cumin accessions to temperature and NaCl and to identify material suitable for stress screening. Temperature and salinity were evaluated in independent completely randomized experiments with four replicates of 50 seeds per accession × treatment combination. Accessions were exposed to four alternating temperature regimes (10/0, 20/10, 30/15 and 40/25 °C) or five NaCl concentrations (0, 50, 100, 150 and 200 mM). Final germination percentage (FGP), mean germination time (MGT), coefficient of variation of germination time (CVt), and germination index (GI) were evaluated using Petri-dish replicates. Seedling vigor index (SVI) was retained as a descriptive supporting metric because the six seedling measurements per accession × NaCl combination could not be linked retrospectively to individual Petri-dish replicates. Mean FGP was 96.3% at 10/0 °C and 94.4% at 20/10 °C, declined to 80.3% at 30/15 °C, and was 0% at 40/25 °C. Under salinity, mean FGP was 81.5% in the control, 90.8% at 50 mM, 87.5% at 100 mM, 68.2% at 150 mM and 44.1% at 200 mM. At 200 mM, C29 retained 78.0% FGP and GI 2.9, whereas C02 retained only 19.5% FGP; C27 retained 57.5% FGP. Descriptive SVI was also highest for C29 at 200 mM (456.9). The high descriptive mean SVI at 150 mM (396.7 versus 303.6 in the control) reflected accession-specific seedling-length responses and should not be interpreted as a statistically tested stimulatory salinity effect. C29 and, secondarily, C27 are promising candidates for further validation. Because temperature and salinity were tested separately and no physiological assays were performed, combined-stress mechanisms and field tolerance require factorial and soil-based confirmation.

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