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

Highlights

• Cumin germination was maximal under cool to moderate alternating regimes (10/0 and 20/10 °C).
• The 40/25 °C regime fully inhibited germination in all nine accessions.
• Low to moderate salinity (50–100 mM NaCl) maintained germination in most accessions.
• C29 and C27 were the most promising accessions for high-salinity germination screening.

1 Introduction

Cumin (Cuminum cyminum L.) is an annual seed spice cultivated widely in warm, dry regions and used as a culinary, medicinal and industrial raw material. Its botanical identity, agronomic value, seed quality and biochemical composition have been described in classical and recent literature (Pimenov and Leonov, 1993; Lal et al., 2014; Mnif and Aifa, 2015; Allaq et al., 2020; Merah et al., 2020; Ahmed et al., 2024; Arshadi-Bidgoli et al., 2024; Arshadi-Bidgoli et al., 2025). Recent studies in Morocco have also highlighted the strategic importance of cumin in oasis and dryland production systems, where it is promoted as a high-value crop adapted to water-limited environments (Bakali et al., 2024; El Amraoui et al., 2024). Because crop establishment depends on successful germination and early seedling growth, this stage can become a major production bottleneck when sowing coincides with large day–night temperature fluctuations, saline soils or low-quality irrigation water (Bewley et al., 2013; Finch-Savage and Bassel, 2016; Mukhopadhyay et al., 2021; IPCC, 2022; Negacz et al., 2022; Bakali et al., 2024; El Amraoui et al., 2024).

In Morocco, substantial variability has been reported among cumin accessions originating from different production regions and countries. Morphological and physical characterization studies demonstrated significant differences in seed size, weight, density and other schizocarp traits according to accession origin, cultivated area and irrigation regime, indicating the existence of valuable genetic and phenotypic diversity that may influence germination behavior and seedling establishment under stress conditions (El Amraoui et al., 2024). In parallel, surveys conducted among Moroccan farmers revealed major differences in seed sources, cultivation practices, irrigation systems and productivity levels, further emphasizing the need to identify adapted and high-performing accessions for sustainable cumin production in salt-affected environments (Bakali et al., 2024).

Salinity is among the most persistent constraints to agriculture in arid and semi-arid environments. Global assessments show that salt-affected soils occupy extensive areas and that secondary salinization is promoted by climate change, intensive irrigation, high evapotranspiration and insufficient drainage (Mukhopadhyay et al., 2021; IPCC, 2022; Negacz et al., 2022). At the plant level, salinity restricts water uptake through osmotic effects, disrupts ion homeostasis, promotes reactive oxygen species accumulation and can impair growth and productivity (Munns and Tester, 2008; Roy et al., 2014; Kumar et al., 2021; Alghamdi, 2024). Germination is especially sensitive because the seed must imbibe water, reactivate metabolism and initiate radicle protrusion before a functional root system is established.

Seed germination is therefore a critical agronomic filter. Final germination percentage describes the capacity of a seed lot to produce seedlings, whereas germination rate, temporal uniformity and seedling vigor influence stand establishment (Ranal and Santana, 2006; Donohue et al., 2010; Bewley et al., 2013; Finch-Savage and Bassel, 2016; De Vitis et al., 2020). Temperature regulates the rate and success of metabolic activation, while salinity reduces external water potential and may impose ion toxicity. Hydrothermal and halothermal approaches demonstrate that seed responses depend on interactions among temperature, water potential and salt effects (Alvarado and Bradford, 2002; Bakhshandeh et al., 2020). Studies across grasses, medicinal plants, cereals, cacti and vegetables confirm that thermal requirements and salinity thresholds vary among species and genotypes, and that temperature can modify the severity of salinity stress (Guo et al., 2020; Liu et al., 2021; Li et al., 2023; Nikolić et al., 2023; Amin et al., 2024; Irik and Bikmaz, 2024; Silva et al., 2025).

In cumin, previous studies have reported negative effects of salts on germination or early seedling growth and have examined seed priming, rhizobacteria, drought stress, plasma treatment and dormancy-related mechanisms (Dodd and Donovan, 1999; Shahi-Gharahlar et al., 2010; Roodbari et al., 2013; Mohammadizad et al., 2014; Shoor et al., 2014; Soltani et al., 2019; Piri et al., 2020; Rasooli et al., 2021; Noori et al., 2022; Moradi et al., 2023). However, the effect of cumin accession on germination performance under temperature and salinity stress remains poorly documented. Limited information is available on how cumin accessions from Moroccan production environments differ in final germination percentage, germination speed, germination uniformity, and early seedling vigor when exposed to alternating temperature regimes and graded NaCl concentrations. Identifying accessions that germinate rapidly and maintain high seedling vigor under saline conditions is essential for improving cumin establishment in dryland systems. Such information can help define practical stress thresholds, support accession screening, and guide breeding or seed-management strategies for salt-affected environments. Therefore, this study aimed to: (i) determine the effect of cumin accession on germination under contrasting alternating temperature regimes; (ii) evaluate germination and early vigor under increasing NaCl concentrations; and (iii) identify accessions with superior germination-stage performance under high-salinity.

2 Materials and methods

2.1 Plant material and accession origin

In 2021, mature seeds of nine cumin (Cuminum cyminum L.) accessions were collected from Moroccan production sites. The material comprised local Moroccan accessions and accessions whose seed source had originally been introduced from Saudi Arabia, Egypt, India, Syria or Turkey. All accessions were identified, coded and labeled at the INRA-Errachidia laboratory. In Table 1, region, province and collection location refer to the Moroccan site where each seed lot was collected in 2021, whereas seed origin/introduction source denotes the reported source country of introduced material or “Local” for Moroccan material. Accession code and elevation are also reported.

Table 1. Origin and collection information of the nine cumin accessions used in the germination experiments.

2.2 Sterilization of seeds

Seeds were surface-sterilized using a laboratory protocol adapted for cumin. For each treatment, seeds of uniform size, shape and color were selected. Seeds underwent two successive disinfection steps with 2% sodium hypochlorite (NaOCl) and were then rinsed thoroughly with sterile distilled water for 2 min to remove residual NaOCl. The archived laboratory record does not specify the duration of each individual NaOCl exposure; this detail is therefore not reconstructed retrospectively.

2.3 Germination protocol

Seeds were placed in 15-cm sterile Petri dishes on two layers of Whatman No. 1 filter paper moistened with 5 mL of distilled water or the corresponding NaCl solution. Petri dishes were closed to limit evaporation and maintain moisture conditions. The archived protocol does not record whether, or according to what schedule, distilled water or NaCl solution was replenished during the 30-day assay; therefore, no replenishment frequency or volume is reported. For each treatment, four replicates of 50 seeds were used. Germination was recorded daily for 30 days and was defined as radicle protrusion of at least 2 mm beyond the seed coat. The protocol follows common seed-testing principles for replicated germination assays (ISTA, 2024).

2.4 Salinity treatments and experimental design

Salinity treatments consisted of five NaCl concentrations: 0, 50, 100, 150, and 200 mM. The 0 mM treatment, prepared with distilled water only, served as the control. NaCl solutions were prepared by dissolving the required mass of analytical-grade NaCl in distilled water to obtain the target concentrations of 50, 100, 150, and 200 mM. Each solution was mixed until complete dissolution and uniform distribution of the salt.

The salinity experiment was arranged in a completely randomized design (CRD) with nine accessions, five salinity treatments and four replicates per treatment. Each replicate consisted of 50 seeds placed at equal distances in a 15-cm Petri dish lined with two layers of Whatman No. 1 filter paper. Each dish received 5 mL of the assigned NaCl solution or distilled water for the control treatment. Petri dishes were maintained under controlled alternating temperature conditions of 20/10 °C. The manufacturer/model of the temperature-controlled unit and any chamber-position rotation or repositioning log were not retained in the archived experimental record. The salinity assay was conducted independently from the temperature assay, using the same replication structure and observation period.

2.5 Temperature treatments

Temperature effects were assessed under four alternating day/night temperature regimes (14 h day/10 h night): 10/0, 20/10, 30/15 and 40/25 °C. The archived protocol retains the 14-h/10-h day/night schedule but does not retain the lamp type or light intensity used during the day phase; these illumination details are therefore not reconstructed retrospectively. These regimes were selected to simulate thermal fluctuations that may occur under field or nursery conditions. The temperature assay was conducted in the absence of NaCl stress, using distilled water as the germination medium.

2.6 Assessment of germination and seedling growth

Seed germination was monitored daily throughout the 30-day experimental period. A seed was considered germinated when the primary root extended at least 2 mm beyond the seed coat. At the end of the salinity assay, seedling length was measured on six germinated seedlings per accession × NaCl combination and used to calculate SVI. The surviving experimental archive does not document the selection rule used to choose these six seedlings, the number of Petri dishes represented by them, or the Petri-dish identity of each measured seedling. Accordingly, the six seedling measurements were treated as subsamples rather than independent experimental replicates. Seedling length was the growth trait retained for SVI calculation; fresh and dry weight were not included among the endpoints reported in this study.

2.7 Germination and vigor indices

The following indices were used to characterize germination and early seedling performance. Final germination percentage was calculated as FGP (%) = (Ng/Nt) × 100, where Ng is the number of germinated seeds and Nt is the total number of seeds. Mean germination time was calculated as MGT = Σ(Di × ni)/Σni, where ni is the number of seeds germinated on day Di. The coefficient of variation of germination time was calculated as CVt (%) = (St/MGT) × 100, where St is the standard deviation of germination time. The germination index was calculated as GI = Σ(Gi/Di), where Gi is the number of seeds germinated on day Di. Seedling vigor index was calculated as SVI = FGP × mean seedling length, following the classical vigor-index approach (Abdul-Baki and Anderson, 1973; Ranal and Santana, 2006). Because the individual seedling measurements used for SVI could not be linked to Petri-dish replicates, SVI was treated as a descriptive supporting metric and was not subjected to factorial ANOVA, effect-size estimation or Tukey multiple comparisons.

2.8 Statistical analysis

The temperature and salinity experiments were analyzed independently as fixed-effects completely randomized designs, with the Petri dish as the experimental unit for the replicated germination variables (FGP, MGT, CVt and GI). Each accession × treatment combination comprised four replicate dishes of 50 seeds. FGP proportions were arcsine square-root transformed before inferential analysis; therefore, FGP was not analyzed on the original percentage scale, although untransformed means ± standard deviation are reported for biological interpretation. For the temperature assay, FGP was analyzed across all four temperature regimes using accession, temperature regime and their interaction as fixed effects (144 experimental units; residual df = 108). Because no seeds germinated at 40/25 °C, MGT, CVt and GI are biologically undefined at this regime and their temperature analyses were restricted to 10/0, 20/10 and 30/15 °C (108 experimental units; accession df = 8, temperature df = 2, interaction df = 16, residual df = 81). For the salinity assay, the model included accession, NaCl concentration and their interaction. Treatment means for inferentially analyzed germination variables were compared using Tukey’s multiple-comparison procedure at α = 0.05. SVI was excluded from inferential models and is presented descriptively because Petri-dish identity was not retained for the six seedling subsamples per accession × NaCl combination.

Analyses were performed with SAS 9.1 and Statgraphics Plus 5.1 following standard principles for factorial experiments (Steel and Torrie, 1980). FGP was analyzed after arcsine square-root transformation to improve variance properties for bounded percentage data, including values close to 0% and 100%. The archived materials available for this revision do not contain the final replicate-level residuals or saved residual-diagnostic output; consequently, formal residual-diagnostic statistics could not be reproduced without reconstructing unobserved data. No normality, homogeneity, exact P-value or effect-size statistics were therefore invented from summary tables. Inferential interpretation is restricted to the independently replicated germination variables, while SVI is reported descriptively.

3 Results

3.1 Temperature response and accession variation

Temperature produced large changes in germination and revealed clear accession-specific responses (Figure 1; Table 2). Mean FGP across accessions was 96.3% at 10/0 °C and 94.4% at 20/10 °C, decreased to 80.3% at 30/15 °C, and fell to 0% at 40/25 °C. The 40/25 °C treatment therefore caused complete germination failure in all nine accessions, a biologically substantial effect rather than a small numerical difference.

Table 2. Germination traits of nine cumin accessions under alternating temperature regimes. .

Values are mean ± standard deviation (n = 4 Petri-dish replicates, 50 seeds per replicate). FGP, final germination percentage; MGT, mean germination time; CVt, coefficient of variation of germination time; GI, germination index. FGP proportions were arcsine square-root transformed for inferential analysis. FGP was analyzed across all four temperature regimes. At 40/25 °C, no seeds germinated; therefore MGT, CVt and GI are not applicable (NA) and no Tukey letters are reported for these indices at that regime. MGT, CVt and GI were analyzed only across 10/0, 20/10 and 30/15 °C. Uppercase letters compare temperature regimes within an accession and lowercase letters compare accessions within a regime for variables/regimes included in the corresponding Tukey analysis.

The 30/15 °C regime was the most discriminating among germinating temperatures. C02 and C27 each retained 92.5% FGP, whereas C19 declined to 27.0% and C33 to 68.5%. C02 also combined the shortest MGT (6.6 days) with the highest GI (8.4) at 30/15 °C. At 20/10 °C, C26 and C27 achieved 100% FGP, while C09 recorded the highest GI (5.4). CVt values further showed that accessions differed in germination synchrony even when final percentages were similar. Thus, interpretation of thermal performance requires both final and time-dependent germination traits.

3.2 Salinity response and accession-specific tolerance

NaCl responses were non-linear at low concentrations and strongly accession-dependent (Figure 2; Tables 3, 4). Mean FGP across accessions 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. The original summary table also reported an overall mean MGT of 14.0 days at 200 mM. Thus, 50–100 mM NaCl did not reduce mean FGP relative to the control, whereas inhibition became pronounced at ≥150 mM.

Table 3. Germination traits and descriptive seedling vigor of nine cumin accessions under 0–150 mM NaCl.

For FGP, MGT, CVt and GI, values are mean ± standard deviation based on four Petri-dish replicates of 50 seeds. FGP, final germination percentage; MGT, mean germination time; CVt, coefficient of variation of germination time; GI, germination index; SVI, seedling vigor index. Uppercase letters compare NaCl concentrations within an accession and lowercase letters compare accessions within a concentration for the replicated germination variables (Tukey, α = 0.05). SVI values are descriptive means based on six measured seedlings per accession × NaCl combination. Because the archival dataset does not retain the Petri-dish identity or dish allocation of these seedlings, no SVI ANOVA, P values, effect sizes or Tukey groupings are reported.

Table 4. Severe-salinity performance of cumin accessions at 200 mM NaCl.

FGP, final germination percentage; GI, germination index; SVI, seedling vigor index. Only variables with documented accession-level values at 200 mM are presented. SVI is descriptive and was not included in inferential comparisons.

At 150 mM NaCl, C09 (92.0%), C29 (91.0%), C19 (88.0%) and C27 (87.5%) maintained high FGP, while C02 declined to 21.0%. At 200 mM (Table 4), C29 remained the highest-performing accession with 78.0% FGP, followed by C27 (57.5%), whereas C02 retained only 19.5%. The 58.5-percentage-point contrast between C29 and C02 at 200 mM is agronomically large. C09 illustrates why screening at a single stress level can be misleading: its FGP declined from 92.0% at 150 mM to 24.0% at 200 mM.

GI also separated tolerant from sensitive accessions under severe salinity. At 200 mM (Table 4), C29 had the highest GI (2.9), whereas C02 and C09 had GI values of 0.6 and 0.8, respectively. These patterns support a multi-trait interpretation of salinity tolerance rather than selection based only on final germination percentage.

Each point is an accession mean based on four Petri-dish replicates of 50 seeds. Replicate variability and Tukey groupings for 0–150 mM are reported in Table 3; the accession-level means reported for 200 mM are summarized in Table 4.

Severe-stress accession means reported at 200 mM are presented separately in Table 4 so that only documented values are shown. FGP and GI are reported as accession-level severe-stress means; SVI is retained as descriptive supporting information only.

3.3 Seedling vigor under salinity and severe-stress interpretation

SVI is presented descriptively because the individual seedling measurements could not be linked to independent Petri-dish replicates (Figure 3; Tables 3, 4). Descriptive mean SVI was 303.6 in the control, 167.7 at 50 mM, 191.3 at 100 mM, 396.7 at 150 mM and 156.1 at 200 mM. The 150 mM peak reflected marked accession differences: C19, C09, C29 and C27 had descriptive SVI values of 736.4, 630.9, 547.3 and 534.5, respectively. At 200 mM, C29 retained the highest descriptive SVI (456.9), whereas C02 and C09 declined to 41.8 and 78.2. Because SVI is calculated as FGP × mean seedling length, a high SVI can arise when the successfully germinated seedlings are relatively long. These patterns are therefore used only as supporting descriptive information and should not be interpreted as statistically tested differences among accessions or salinity treatments.

4 Discussion

4.1 Thermal requirements and the high-temperature inhibition threshold

The temperature experiment identifies a broad favorable window at 10/0–20/10 °C and a clear upper inhibition threshold at 40/25 °C. Cardinal-temperature theory predicts declining germination when incubation exceeds the supra-optimal range (Alvarado and Bradford, 2002; Bewley et al., 2013; Finch-Savage and Bassel, 2016; Bakhshandeh et al., 2020), and the complete absence of germination at 40/25 °C indicates that this alternating regime exceeded the germination tolerance of every accession tested. This response is agronomically relevant because seed-zone temperatures during sowing can be much higher than air-temperature averages in arid environments. Recent studies in other crops likewise show genotype- and species-specific thermal thresholds and strong temperature effects on stress expression (Guo et al., 2020; Liu et al., 2021; Li et al., 2023; Nikolić et al., 2023; Amin et al., 2024; Irik and Bikmaz, 2024; Silva et al., 2025; Han et al., 2026).

The distinction between final germination and germination timing is important. Although 10/0 °C produced very high FGP, some accessions germinated more slowly, whereas 20/10 °C combined high FGP with generally favorable MGT and GI. For nursery or field establishment, this balance is more useful than FGP alone because rapid, synchronous emergence reduces the period during which newly germinated seedlings remain exposed to adverse conditions (Ranal and Santana, 2006; Donohue et al., 2010; Bewley et al., 2013; Finch-Savage and Bassel, 2016; De Vitis et al., 2020; Romano and Stevanato, 2020; Onofri et al., 2022; Sedghi, 2025).

The 30/15 °C regime revealed otherwise hidden accession differences. C02 maintained 92.5% FGP with MGT of 6.6 days and GI of 8.4, while C19 fell to 27.0% FGP. This contrast suggests that 30/15 °C can serve as a discriminating temperature in germination-stage screening, although validation under soil conditions is required before it is used as a breeding threshold.

4.2 Salinity response and low-dose stimulation

Salinity did not reduce mean FGP at 50–100 mM, but 150 and especially 200 mM clearly separated tolerant from sensitive accessions. Low-dose responses should be interpreted cautiously. Mild external osmotic adjustment can sometimes alter imbibition dynamics without producing the ion toxicity associated with stronger salt stress, but Petri-dish responses cannot be equated with field tolerance because soils contain heterogeneous salt distributions, changing water contents and rhizosphere interactions (Dodd and Donovan, 1999; Munns and Tester, 2008; Roy et al., 2014; Kumar et al., 2021; Valenzuela et al., 2022; Wang et al., 2022; Alghamdi, 2024). The increase in FGP observed in some accessions at 50–100 mM is therefore described as a laboratory response, not as proof of beneficial salinity.

The severe-stress ranking is most reliably interpreted from the independently replicated germination variables. At 200 mM, C29 combined 78.0% FGP with GI 2.9, whereas C02 had 19.5% FGP and GI 0.6; C27 retained 57.5% FGP. The descriptive SVI values (456.9 for C29 and 190.2 for C27) support, but do not statistically establish, the same ranking. By contrast, C09 performed strongly at 150 mM but declined to 24.0% FGP at 200 mM. These cross-over responses show that tolerance ranking depends on stress intensity and on the trait used for selection, a pattern also reported in recent genotype-screening studies (Romano and Stevanato, 2020; Onofri et al., 2022; Valenzuela et al., 2022; Wang et al., 2022; Sanehkoori and Bakhshandeh, 2023; Aggarwal et al., 2024; Fang et al., 2024; Mastroberardino et al., 2025; Sedghi, 2025).

4.3 Multiple indices provide a more reliable tolerance interpretation

Using complementary germination metrics is a strength of the study because the independently replicated FGP, MGT, CVt and GI capture different components of establishment, while descriptive SVI provides supporting information on early seedling growth. FGP reflects the proportion of seeds that complete germination, GI integrates final percentage with speed, and CVt reflects temporal dispersion. SVI combines germination with early seedling length but, in the present dataset, cannot be used for inferential accession or salinity comparisons because seedling subsamples were not traceable to Petri-dish replicates. Recent methodological work recommends complementary germination metrics because a treatment may delay germination without preventing it, or may allow radicle protrusion while constraining subsequent growth (Romano and Stevanato, 2020; Onofri et al., 2022; Sedghi, 2025).

The most unusual descriptive result was the high SVI at 150 mM. Because SVI = FGP × mean seedling length, the reported values are arithmetically compatible with successfully germinated seedlings attaining relatively high elongation. For example, the C19 summary (SVI 736.4 with FGP 88.0%) implies a mean seedling length of approximately 8.37 in the measurement units used, while C09 implies approximately 6.86. This arithmetic explains how descriptive SVI can rise even while population-level stress is increasing; it does not establish a hormetic or physiological stimulation mechanism and, because SVI was not analyzed at the Petri-dish level, it should not be interpreted as a statistically significant salinity response. Selection among survivors, accession-specific reserve use and elongation responses are plausible explanations, but they require raw seedling-length, ion and biochemical measurements for confirmation.

4.4 Relationship with previous cumin studies and seed enhancement strategies

Earlier cumin studies have documented reductions in germination and early growth under salinity and have explored priming, rhizobacteria, plasma treatment and dormancy management (Shahi-Gharahlar et al., 2010; Roodbari et al., 2013; Mohammadizad et al., 2014; Shoor et al., 2014; Soltani et al., 2019; Piri et al., 2020; Rasooli et al., 2021; Noori et al., 2022; Moradi et al., 2023). The present study adds accession-level screening and shows that genetic or seed-lot background can strongly modify stress response. Mechanistically, salt tolerance in plants may involve osmotic adjustment, Na+ exclusion or compartmentation, maintenance of K+ homeostasis, membrane protection and control of reactive oxygen species through antioxidant systems (Munns and Tester, 2008; Roy et al., 2014; Kumar et al., 2021; Alghamdi, 2024; Zhang et al., 2025). However, none of these mechanisms was directly measured here, so they are used only to frame testable hypotheses.

The high SVI at 150 mM should therefore be discussed as a composite growth response rather than as evidence that NaCl stimulated biomass accumulation. The study measured seedling length for SVI but did not quantify ion content, osmolytes, reactive oxygen species, antioxidant enzymes or post-germination survival. Recent combined-stress work demonstrates that temperature can modify salt-induced oxidative and antioxidant responses, reinforcing the need for mechanistic measurements in a future factorial experiment (Han et al., 2026).

4.5 Study limitations and scope of inference

The present work should be interpreted as controlled germination-stage screening rather than a complete field-tolerance assessment. First, temperature and salinity were studied in independent experiments, so no temperature × salinity interaction can be inferred. This limitation matters because combined stresses can produce responses that are not predictable from single-factor experiments (Nikolić et al., 2023; Amin et al., 2024; Han et al., 2026). Second, Petri-dish NaCl treatments do not reproduce heterogeneous soil salinity, fluctuating water potential, soil structure or rhizosphere processes. Third, no physiological or biochemical traits were measured; explanations involving osmotic adjustment, ion toxicity, antioxidant defense or stress memory therefore remain hypotheses (Munns and Tester, 2008; Roy et al., 2014; Kumar et al., 2021; Alghamdi, 2024; Zhang et al., 2025). Finally, each accession was represented by a collected seed lot, so genetic effects cannot be fully separated from maternal environment and seed-lot history.

A further limitation concerns the statistical archive. The materials retained for the present revision contain treatment summaries and Tukey groupings for the replicated germination variables but do not include the final replicate-level residuals or saved diagnostic output required to reproduce formal model-assumption tests independently. Accordingly, no residual statistics, exact P values or effect sizes were reconstructed from rounded summary tables. FGP was analyzed after arcsine square-root transformation because percentage observations included values near the boundaries of 0% and 100%, and the inferential conclusions are interpreted cautiously in light of the unavailable residual archive.

4.6 Agronomic implications and future research

For breeding and germplasm screening, C29 should be prioritized as the leading candidate for validation under severe salinity because it combined the strongest independently replicated germination performance at 200 mM (78.0% FGP and GI 2.9); its high descriptive SVI provides supporting evidence only. C27 is a useful secondary candidate because it retained 57.5% FGP, whereas C02 can serve as a sensitive comparator. Screening at both 150 and 200 mM is preferable to a single concentration because accessions such as C09 changed rank sharply between the two levels. For seed production and quality control, high germination under non-stress conditions should not be treated as a proxy for salt tolerance; stress-screening of candidate seed lots can provide additional discrimination.

For crop establishment, the results support avoiding sowing or nursery conditions that approach the 40/25 °C alternating regime and favoring cooler germination windows when agronomically feasible. These recommendations remain provisional until soil-based validation. Future work should combine temperature and salinity factorially, quantify emergence and seedling survival, and measure Na+/K+ balance, proline or soluble sugars, membrane integrity, reactive oxygen species, antioxidant-enzyme activity, root architecture and yield. Hydrothermal or halothermal modeling could then estimate accession-specific base, optimum and ceiling thresholds and improve prediction under fluctuating field conditions (Alvarado and Bradford, 2002; Bakhshandeh et al., 2020; Amin et al., 2024; Han et al., 2026).

5 Conclusion

Temperature and salinity strongly shaped cumin germination, with substantial accession-level variation. The most favorable alternating regimes were 10/0 and 20/10 °C, while 40/25 °C completely inhibited germination. Salinity responses were concentration-dependent: 50–100 mM maintained high mean FGP, 150 mM separated tolerant from sensitive material, and 200 mM imposed severe inhibition. C29 showed the strongest severe-salinity performance based primarily on the independently replicated germination variables (78.0% FGP and GI 2.9 at 200 mM), and C27 retained 57.5% FGP. Descriptive SVI supported the promising performance of C29 but was not used for inferential ranking because seedling subsamples could not be linked to Petri-dish replicates. These accessions are therefore promising candidates for breeding and seed-system evaluation, not yet field-proven tolerant cultivars. Because temperature and salinity were tested independently and physiological mechanisms were not measured, factorial experiments and greenhouse/field validation are required before definitive mechanistic or agronomic recommendations are made.

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Footnotes

Edited by: Jose Ramon Acosta Motos, Catholic University San Antonio of Murcia, Spain

Reviewed by: Habtamu Chekol Fantahun, Ababa University, Ethiopia

Brahim Ouahzizi, Mohammed VI Polytechnic University, Morocco