*2.5. Physiological and Agronomic Measurements*

Chlorophyll index (soil-plant analysis development (SPAD) value) and gas exchange measurements, including stomatal conductance (*gs*), photosynthesis (*Pn*), and transpiration rate (*Tr*), were measured at three different growth stages: development (35 DAS), mid (63 DAS), and late stage (83 DAS). One leaf (of the same age) was selected per plant from five plants per plot. A total of 15 measurements per treatment were made at every growth stage.

The chlorophyll index (SPAD value) was measured using a SPAD 502 Plus Chlorophyll Meter (Minolta Co. Ltd., Osaka, Japan). Using a chlorophyll meter is a non-destructive method that quickly and precisely approximates the chlorophyll concentration of leaves by measuring the red (650 nm) and infrared (940 nm) radiation of leaves [42]. The sample readings were made for every plot using the center section of the selected leaf at all measured growth stages.

The gas exchange measurements *gs*, *Pn*, and *Tr* were measured using an LI-6400XT portable photosynthesis system (LiCor Inc., Lincoln, NE, USA). The samples were measured for each treatment from functional leaves on a cloudless day from 08h00 to 10h00 local time.

Total fresh squash yields (Mg ha−1) were determined by manually collecting and weighing fruits from each line for all harvested squash fruits. The irrigation water use efficiency (IWUE) was calculated by dividing the total weight of harvested squash fresh fruits (kg ha<sup>−</sup>1) by the volume of water applied to the crop (m3 ha<sup>−</sup>1) [9,10].

The fruit quality parameters, total soluble solids (*TSS*, %), vitamin C (*VC*, mg 100 g−<sup>1</sup> fruit fresh weight-FW), and titratable acidity (*TA*, % citric acid), were assessed by choosing samples of three mature fruits in the third, fifth, and seventh harvestings per treatment in each growing season. A squash extract was taken by blending and filtering the flesh of each fruit. A digital refractometer (PR-101 model, ATAGO, Tokyo, Japan) was used to determine the TSS using standard methods of analysis [43], while TA was determined using the procedure, described by Caruso et al. [44]. 2,6-dichlorophenol-indophenol-dye was used to measured Vc in the extracted juice [45].
