Evaluation of Durum Wheat Genotypes at Germination Stage under Salinity Stress †

: The aim of this work was to investigate several durum wheat genotypes (eleven landraces, two old varieties and seven modern cultivars) for salt tolerance at germination and early growth stages. Seeds were tested under two different concentrations of NaCl solution (50 mM and 100 mM) and a control (T) with distilled water. Experiments were laid out in a two-factorial design with three replications. Two-way ANOVA was performed and means were compared with Duncan’s Multiple Range test. Seven parameters were measured under laboratory conditions: germination, mean germination time, shoot length, root length, root number, shoot dry matter and root dry matter. Rusticano, with the highest value of root number (5.44), was statistically different from all other genotypes. Timilia reste bianche, Timilia reste nere, Ciciredda and Cappelli are highlighted for the best root length performance at 100 mM.


Introduction
Salinity is one of the most severe abiotic stress factors affecting plant growth and agricultural production worldwide.It affects almost 1 billion ha worldwide, globally representing about 7% of the continental extent of the earth [1].Agricultural crops exhibit a wide spectrum of responses under salt stress.Salinity affects almost all aspects of plant development including germination, vegetative growth and reproductive development.It strongly inhibits seed germination through osmotic stress, ion-specific effects and oxidative stress.Sicily, with its variable pedoclimatic conditions, is an important source of agrobiodiversity.In this context, over recent centuries, farmers have made a continuous selection that has led to the creation of numerous landraces.
Landraces are named and maintained by traditional farmers to meet their social, economic, cultural and environmental needs.Durum wheat [(Triticum turgidum L. subsp.durum (desf.)Husn.] is a typical Sicilian crop with a cultivated area of about 270,000 ha, although on small areas (about 5000 ha), in the last decade, the cultivation of landraces has been reintroduced [2].Landraces, which have arisen through a combination of natural selection and the selection performed by farmers, usually have a broader genetic base and can therefore provide valuable characteristics important for breeding.To date, 24 Sicilian durum wheat landraces are listed in the national register of varieties (https://www.sian.it/portale-sian/home.jspconsultation in 22 July 2023).Information on the genotypic tolerance to salt stress during the germination process is lacking in Sicilian durum wheat landraces.Limited literature work has been documented so far on these genotypes, so knowing their behavior can help breeding programs in the selection of salt-tolerant varieties to achieve optimum wheat growth under saline conditions.The aim of this work was to investigate several durum wheat genotypes (eleven landraces, two old varieties and seven modern cultivars) for salt tolerance at germination and early growth stages.

Materials and Methods
Laboratory experiments were conducted to evaluate the germination traits of 20 durum wheat genotypes at the Council for Research in Agriculture and Economics-Research Centre for Plant protection and Certification Palermo, Italy in 2023.The seeds of all the genotypes tested were obtained in our experimental station during the growing season 2021/2022 and stored at 5 • C with 30% relative humidity.
Seven modern varieties of durum wheat (Ciclope, Duilio, K-26, Mongibello, Quadrato, Rusticano and Simeto), two old varieties (Capeiti 8 and Trinakria) and eleven landraces (Cappelli, Castiglione glabro, Ciciredda, Francesa, Perciasacchi, Russello, Russello Ibleo, Scorsonera, Timilia reste bianche, Timilia reste nere and Urria) were assessed.Seeds were tested under 2 different concentrations of NaCl solution (50 mM and 100 mM) and a control (T) with distilled water.Seeds were surface-sterilized in 5% sodium hypochlorite solution for 3 min and washed thoroughly under tap water for 10 min and at the end with distilled water.To avoid water losses, the edges of Petri dishes were tightly sealed with an impermeable colorless parafilm.Seeds were allowed to germinate at 20 • C in the dark.
To each Petri dish, sterilized in an oven at 120 • C for 2 h, 12 mL of solution was added to keep the filter paper uniformly soaked without flooding.Fifty randomly selected seeds for each variety were placed in Petri dishes with a 13.5 cm diameter (one replication was made up of 2 Petri dishes containing 25 seeds each) on a double layer of Whatman filter paper No. 1 with the crease facing down and kept in a thermostatic cabinet (KW Scientific Equipment model WRS 85).Shoot and root lengths and fresh and dry weights were recorded after 7 days.Data for shoot and root lengths were obtained from 50 seedlings in each replication.
The seedlings' fresh and dry weights were taken with the help of a digital balance (Mettler Toledo PR503 Delta Range); dry weight was measured by placing them at 80 • C in a hot air oven for 24 h until a constant weight was observed.
Experiments were laid out in a two-factorial design with three replications using a complete randomized design (CRD).A two-way ANOVA was performed and means were compared with Duncan's Multiple Range test at a 5% level of probability.The assumption of normality and homoscedasticity was verified with Shapiro-Wilk and Levene's tests, respectively.
Seven parameters were measured under laboratory conditions: germination, mean germination time (MGT), shoot length, root length, root number, shoot dry matter and root dry matter.
Germination percentages were recorded daily up to the 7th day using radicle extrusion (≥2 mm long) as a criterion.A seed was considered to show abnormal germination if shoot growth occurred in the absence of radicle extension.They are expressed as the ratio of germinated seeds on the 7th day to the total number of seeds using the following formula: G = (c/a) × 100 where a = total number of seeds, c = number of germinated seeds on the 7th day.
Mean germination time (MGT, days): This parameter is determined according to the following formula [3]: where n is the number of seeds germinated on day i, d is the incubation period in days, and b is the total number of seeds germinated upon treatment.
To compute shoot and root dry matter, the following formula was used: Dry matter (%) = (Dry weight/fresh weight) × 100

Results
Genotype, concentration and their interaction showed significant differences in many of the parameters studied (Table 1).Rusticano showed the highest value of root number (5.44), statistically different from all other genotypes; however, Timilia reste nere, Timilia reste bianche, Cappelli, Ciciredda were characterized by the lowest values.
In general, modern varieties showed significantly higher shoot dry matter values than landraces except for Francesa, Scorsonera and Russello Ibleo.
A rise in NaCl concentration determined an increase in the mean germination time and shoot dry matter; mean germination time passed from 2.31 days (control) to 2.38 days (50 mM) and 2.43 days (100 mM), while shoot dry matter varied from 8.92 (control) to 10.04 (100 mM).Increasing the concentration of NaCl in the solution led to a significant reduction in shoot length from 7.73 cm (control) to 5.67 cm (100 mM).The root number was higher at 50 mM (Figure 1).
A rise in NaCl concentration determined an increase in the mean germination time and shoot dry matter; mean germination time passed from 2.31 days (control) to 2.38 days (50 mM) and 2.43 days (100 mM), while shoot dry matter varied from 8.92 (control) to 10.04 (100 mM).Increasing the concentration of NaCl in the solution led to a significant reduction in shoot length from 7.73 cm (control) to 5.67 cm (100 mM).The root number was higher at 50 mM (Figure 1).Remarkable germination values, at 100 mM, were obtained by Timilia reste nere (98.67%),Ciclope (98.00%),Mongibello (96.67%) and Timilia reste bianche (96%); in particular, Timilia reste nere showed the highest value, statistically different from the two modern varieties Duilio and Quadrato; Trinakria, Scorzonera, Russello and Russello Ibleo reported the lowest ones, statistically different from all other genotypes.
At 50 mM, the landraces Cappelli, Urria, Timilia reste bianche and Timilia Reste nere showed good performance of germination, while Trinakria, with the lowest value, was statistically different from the other varieties tested.
At 50 mM, the landraces Cappelli, Urria, Timilia reste bianche and Timilia Reste nere showed good performance of germination, while Trinakria, with the lowest value, was statistically different from the other varieties tested.

Discussion
Seed germination is a major factor limiting the establishment of plants under saline conditions.As supported by the available literature [4][5][6][7], our results confirm that durum

Figure 1 .
Figure 1.Influence of concentration on (a) Mean germination time (MGT); (b) Shoot dry matter (%); (c) Shoot length (cm); (d) Root number.Means followed by the same letter are not statistically different according to Duncan's Multiple Range test at the 5% probability level.

Figure 1 .
Figure 1.Influence of concentration on (a) Mean germination time (MGT); (b) Shoot dry matter (%); (c) Shoot length (cm); (d) Root number.Means followed by the same letter are not statistically different according to Duncan's Multiple Range test at the 5% probability level.

Table 1 .
Factorial analysis of variance.

Table 2 ,
Rusticano, Ciclope, Simeto and Mongibello are notable for the significantly shorter mean germination times (ranging from 2.15 to 2.20 days) compared to Cappelli, Francesa, Perciasacchi and Russello Ibleo (ranging from 2.43 to 2.68 days).In general, all the landraces were reported to have better shoot lengths than modern varieties; the top values are for Ciciredda, Scorsonera, Timilia reste nere and Timilia reste bianche with 7.95, 7.85, 7.76 and 7.69 cm, respectively, values significantly higher than all modern varieties.

Table 2 .
Influence of genotype on some parameters studied.

Table 3 .
Influence of the concentration×genotype interaction on some parameters studied.

Table 3 .
Influence of the concentration × genotype interaction on some parameters studied.In each column, means followed by the same letter are not statistically different according to Duncan's Multiple Range test at the 5% probability level.