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This work aimed to optimize the extraction conditions of bioactive compounds obtained from three squash by-products (e.g., peel, endocarp, and seeds) using the response surface methodology (RSM). The selected independent variables were ethanol concentration, extraction time, and extraction temperature. Squash by-products' bioactive molecules were extracted according to the matrix proposed by the experimental plan. Significant variability in total phenolic compound content (TPC) and antioxidant activity, depending on the extraction time, the solvent concentration, and the extraction temperature, was recorded for the tested by-products. The experimental results adequately fitted with second-order polynomial models and showed significant linear, quadratic, and interaction effects of the independent variables. Data analysis suggested that the optimal extraction conditions were 12.2% ethanol for 11.2 min at 55 °C for peels; 28.5% ethanol for 10.5 min at 37 °C for endocarp; and 20% ethanol for 10.5 min at 60 °C for seeds. The results obtained showed that the experimental and predicted values of TPC and antioxidant activities as an indicator of a successful extraction fit with each other, thus indicating the optimal extraction conditions. Under these conditions, the obtained extracts exhibited high, although variable, TPC with epicatechin and epigallocatechin as major compounds, as well significant antimicrobial potency, which reached 100% and 80% inhibition of the tested bacteria and fungi. [ABSTRACT FROM AUTHOR]

Duch. is one of the most diversified Cucurbita species worldwide. The objective of this study was to evaluate the genetic relationship between and within Tunisian and Italian Cucurbita maxima germplasm collections using morphological and molecular markers. The phenotypic parameters showed a large qualitative variability, primarily according to fruit-related traits, for both collections. The RAPD, ISSR and SRAP molecular marker systems used turned out to be effective in discriminating all the accessions. Among the Tunisian collection, the polymorphic information content (PIC) and genetic diversity (H) values were of 0.461 and 0.50 respectively, with a total of 96% of polymorphism detected. The Italian collection revealed a PIC and H values of 0.454 and 0.50 respectively and 90% of polymorphism. Population structure analysis reflected the geographical origin of the accessions and helped to classify the Tunisian collection into two populations and to group all the Italian accessions into one. The results suggest that the combination of morphological and molecular approaches is a highly reliable technique in studying and evaluating Cucurbita maxima germplasm which represents an important genetic resource to be preserved and used in breeding programs. [ABSTRACT FROM AUTHOR]

Sodic soils reduce growth and production of most vegetables, including sesame (Sesamum indicum L.), and NaCl interferes with the nutrient balance of the rhizosphere. A greenhouse experiment was undertaken to investigate the effects of calcium nitrate fertigation and NaCl concentration on growth and development of sesame. The NaCl concentrations applied in the irrigation water were 0, 30, 70, or 100 mM, and the calcium nitrate levels were 0 or 100 mg·L−1. Leaf area and shoot dry weight did not change with addition of calcium nitrate (100 mg∙L−1) at all NaCl levels. At 100 mM, plants supplemented with 100 mg∙L−1 calcium nitrate produced 51% and 136% more chlorophyll (a) and carotenoids, respectively, and enhanced proline content by 45% and total soluble proteins by 25%. Calcium nitrate supplemented plants accumulated more Na+ ions at roots (+26%) and less Na+ ions at leaves (−20%). These plants generally had higher K+ content at roots (+30%) and at leaves (+94%) owing to 100 mM NaCl. Calcium nitrate (100 mg·L−1) enhanced catalase activity (+43%) and phenolic compounds. Calcium nitrate supplemented plants (100 mg∙L−1) accumulated less malondialdehyde (−50%) and had the highest antioxidant activity compared to 0 mg·L−1. Calcium nitrate may be used to moderate some adverse physiological effects of NaCl for sesame in sodic soils. However, the calcium nitrate concentration was not sufficiently high to benefit yield. [ABSTRACT FROM AUTHOR]

Tunisia, other countries in northwestern Africa, and the Iberian Peninsula, represent a center of diversity of Daucus. The genus traditionally has included about 20-25 species worldwide, but a recent molecular study redefined and expanded Daucus to include representatives from nine other genera. By this classification, Daucus now contains about 40 species, with some of them having winged fruits in addition to its traditionally recognized spiny fruits. The taxonomy of Daucus in Tunisia has recently been studied with morphological data, concluding that D. carota subsp. capillifolius is a subspecies that co-occurs and crosses with subsp. carota. The present study extends these findings with additional data from Genotyping-by-Sequencing (GBS) from 33 Tunisian accessions of D. carota (93 individuals with two to three replicates per accession), including the first collections of subsp. gummifer from Tunisia. Placed in the context of additional GBS data, D. carota subsp. gummifer has separate origins from other collections of subsp. carota in Tunisia and/or immediately adjacent areas to the north in Italy or its surrounding islands. Our results add support to the utility of large SNP datasets for species-level phylogenetic studies in Daucus. [ABSTRACT FROM AUTHOR]

Introduction: Drought stress is one of the most devastating environmental stressors, especially in the arid and semi-arid regions of the world. Considering the major constraints that drought stress poses to crop production and the consequent yield losses in food crops, breeding for climate-resilient crops is an efficient means to mitigate stress conditions., Materials and Methods: This study aimed at evaluating the response of four squash ( Cucurbita maxima Duchesne) landraces to drought stress at germination and at plant stage. Drought stress was induced by different concentrations of D-mannitol (-0.24, -0.47 and -0.73 MPa). The tested parameters at germination stage included germination percentage, seedling vigor index, seed water absorbance and seedling growth potential. At the plant stage, leaf chlorophyll and carotenoids content, chlorophyll fluorescence, evapotranspiration, photosynthesis activity and several biomarkers, namely malondialdehyde, proline, total phenols content, total flavonoids content and DPPH radical scavenging activity were evaluated in both roots and leaves., Results and Discussion: Our results indicate a magnitude of drought stress effects reflected via repression of germination and seedling growth as well as adjustments in physiological functions at later growth stages, in a genotype depended manner. Among landraces, "751" and "746" showed better performance, as evidenced by higher seed germination and seedling growth potential even at high stress levels (-0.47 and - 0.73 MPa), whereas "747" was the most sensitive landrace to drought stress at both tested stages. In conclusion, our findings highlight the importance of squash landraces selection for the identification of elite genotypes with increased tolerance to drought stress., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Saadaoui, Tarchoun, Msetra, Pavli, Falleh, Ayed, Amami, Ksouri and Petropoulos.)