*3.1. Plant Growth and Biomass Production*

The statistical analysis revealed intrinsic genotypic differences, and a genotypic specific response to the NaCl concentration in the nutrient solution in terms of number of leaves, shoot diameter, shoot length, and root length (Table 2). Compared to non-saline seedlings, under 150 mM NaCl, the number of leaves decreased significantly only in the melon genotype CM5 (−31%) while it did not vary significantly in the other genotypes (Figure 1a). Shoot diameter between the genotypes grown under 0 mM NaCl was higher in the interspecific hybrid CMM-R1 (on average 4.6 mm) and bottle gourd genotypes LS1, LS3, and LS4 (on average 4.66, 4.73, and 4.73 mm respectively), whereas bottle gourd LS2, watermelon CV3, and melon (CM9, CM10, CM14, and CM15) seedlings turned out to be thinner (Figure 1b). The genotype and the NaCl concentration significantly affected shoot diameter (Table 2); as a result, 150 mM of NaCl increased shoot diameter by 47% and 36% in CM10 and CV3 genotypes, respectively, while it decreased by −26% in CMM-R1 *C. maxima* × *C. moscata* hybrid and it did not vary in the other genotypes (Figure 1b). Shoot length was significantly affected by the genotypes (Table 2). Particularly, among seedlings grown in the absence of salt stress, melon genotypes (CM3, CM7, CM8, CM9, CM13, and CM16) produced the longest shoots, while the shortest were observed in bottle gourd LS2, watermelon (CV3, CV4, CV5, CV6) and the interspecific hybrids CMM-R1 and CMM-R2. (Figure 1c). A genotypic response to the NaCl concentration was also observed in shoot length (Table 2). Accordingly, compared to seedlings grown under 0 mM NaCl, shoot length in saline grown seedlings decreased significantly in all the tested genotypes except for the watermelon (CV3, CV4, and CV6), bottle gourd (LS1, LS2) genotypes, and the luffa (LC1) (Figure 1c). Seedling root length was significantly different among the genotypes. In fact, under 0 mM NaCl, melon CM5 developed the longest root while melon CM16 and watermelon CV3 the shortest (Figure 1d). On the other hand, when 150 mM NaCl was applied, no significant differences in root length compared to control conditions were observed in the studied genotypes.

**Table 2.** Leaf number (*n* plant<sup>−</sup>1), shoot and root length (cm), shoot diameter (mm), shoot and root dry weight (DW, g plant<sup>−</sup>1), and dry matter content (DM, %) in seedlings of sixteen *Cucumis melo* L., six *Citrullus vulgaris* Schrad., two *C. maxima* × *C. moschata*, four *Lagenaria siceraria* (Molina) Standl. different genotypes, and *Cucurbita moschata* Duch. *cv* 51–17 and *Lu*ff*a cylindrica* Mill. grown at 0 or 150 mM of NaCl. (1 week after the beginning of the treatment). Non significance or significance differences at *p* ≤ 0.05, 0.01, or 0.001 are indicated as: ns, \*\* and \*\*\* respectively.


**Figure 1.** Plant growth, after one week of NaCl treatment, in term of number of leaves (**a**), shoot diameter (**b**), shoot length (**c**), and root length (**d**) in seedlings of sixteen *Cucumis melo* L, six *Citrullus vulgaris* Schrad., two *C. maxima* × *C. moschata*, four *Lagenaria siceraria* (Molina) Standl. different genotypes, and *Cucurbita moschata* Duch. *cv* 51–17 and *Luffa cylindrica* Mill. Mean values ± standard errors; *n* = 3 followed by different letters within each parameter are significantly different based on Duncan post hoc (*p* < 0.05).

#### *3.2. Plant Biomass Production*

The statistical analysis revealed intrinsic genotypic differences, and a genotypic specific response to the NaCl concentration in terms of shoot and root dry weight and dry matter content (Table 2). Under non-saline conditions, melon genotypes CM12 and CM13, together with CMM-R1, produced

heavier shoots while watermelon CV3 the lightest (Figure 2a). As compared to 0 mM NaCl, shoot dry weight between the genotypes was differently affected by 150 mM NaCl. A significant decrease in shoot dry weight was observed in melon (CM2, CM3, CM5, CM7, CM8, CM9, CM12, and CM13) as well as in CMM-R1, CMO 51–17, watermelon (CV1, CV2), and bottle gourd LS2, while it increased in CMM-R2, watermelon CV3, and bottle gourd LS1 and did not vary in the other genotypes (Figure 2a). In the absence of salinity, root dry weight was higher in watermelon CV4, followed by bottle gourd (LS3 and LS4), while the lowest root dry weights were recorded in melon genotypes (CM6, CM15, and CM16) (Figure 2b). When 150 mM NaCl was applied, root dry weight only decreased in CV4 (−79%), while it was not affected in the other genotypes (Figure 2b). Shoot dry matter content differed between the genotypes at both NaCl concentrations. Under 0 mM NaCl, the highest biomass accumulation was observed in watermelon CV6 while the lowest was associated with melon CM1 (Figure 2c). Furthermore, 150 mM (NaCl) resulted in significant increases in shoot dry matter in the bottle gourd genotypes (LS1, LS3, and LS4), together with watermelon (CV2, CV3, and CV5), melon CM1, and both the CMM-R1 and CMM.R1 interspecific hybrids (with the strongest accumulation registered in CMM-R2) (Figure 2c). Differences in root dry matter percentage were associated with genotypes and their interaction with salinity (Table 2). Moreover, under 0 mM NaCl, the highest root biomass content was observed in melon (CM2, CM3, and CM5), while the lowest in bottle gourd (LS1, LS3, and LS4) (Figure 2d). Compared to 0 mM NaCl, root dry matter content decreased in seedlings grown under 150 mM of NaCl of CMO 51–17 (−26%), melon CM3 (−8%), CM10 (−23%), CM11 (−20%), and the interspecific hybrids (CMM-R1: −18%) and (CMM-R2: −48%), while it significantly increased in melon (CM1, CM4, CM5, CM6, CM7, CM8, CM15, and CM16), together with watermelon (CV1, CV2, CV3, CV4, and CV5) (Figure 2d).
