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Soil fertility is declining in low-input agriculture due to insufficient fertilizer application by small-scale farmers. On the other hand, concerns are rising regarding the environmental pollution of both air and water in high-input agriculture due to the excessive use of N fertilizers in short growing seasons for vegetable crops, which is directly linked to the health of human beings and environmental safety. This study aimed to determine genotypic differences in the Nitrogen Use Efficiency (NUE) levels of different leafy vegetable species (Arugula, Spinach, Cress, Parsley, and Dill) grown hydroponically under two different N rates, low N (0.3 mM) and high N (3.0 mM), and to identify the plant traits that are contributing to NUE. A nutrient solution experiment was conducted between March and April 2024 by using an aerated Deep-Water Culture (DWC) technique in a fully automated climate room with a completely randomized block design (CRBD) with three replications for five weeks. The results indicated that shoot growth, as well as root morphological and leaf physiological responses, was significantly (p < 0.001) affected by genotype, the N rate, and genotype–N rate interactions. Shoot growth in some vegetable species (Arugula, Spinach, and Cress) was significantly higher under a low N than a high N rate, illustrating that they have a great capability for NUE under low N stress conditions. Similar results were also recorded for the root growth of the N-efficient species under low N rates. The NUE levels of these species were closely associated with leaf physiological (leaf area, leaf chlorophyll index (SPAD), photosynthesis, and total leaf chlorophyll (a + b) and carotenoids) and root morphological (root length, root volume, and average root diameter) characteristics. These plant traits could be useful indicators for the selection and breeding of ‘N-efficient’ leafy vegetable species for sustainable low-input agriculture systems in the future. However, further investigation should be carried out at the field level to confirm their commercial production viability.

To assess whether grafting could improve the nitrogen (N) efficiency of potato cultivars and to determine which physiological and morphological characteristics are predominantly contributing to N efficiency, a hydroponic experiment was conducted. Two contrasting potato cultivars (Agria: N‑efficient and Van Gogh: N‑inefficient) were grafted reciprocally onto each other. Grafted and non-grafted control plants were grown in a growth chamber for 42 days in 8 L pots filled with continuously aerated nutrient solution under two N rates (Low-N : 0.5 mM N and High-N : 3.0 mM N) by using a deep water culture (DWC) technique. The shoot and root fresh (FW) and dry (DW) weights, main stem length, number of leaves, total leaf area, photosynthetic activity of leaves, shoot and root N concentration, total N uptake, total root length and root volume of potato plants were significantly increased with increased N rate. The grafted plants produced significantly higher above ground biomass than non-grafted ones, indicating that N efficiency was significantly improved by the reciprocally grafting under low and high N rates. Non-grafted cv. Agria showed higher numbers of shoot and root FW and DW, total leaf area, intensity of photosynthesis net measurements, compared to non-grafted cv. Van Gogh under both N rates. In reciprocal grafting, the growth performance of cv. Agria slightly increased when it was grafted onto cv. Van Gogh, whereas a significant increase in crop growth performance was recorded when cv. Van Gogh was grafted onto cv. Agria. The N efficiency of non-grafted cv. Agria was closely associated with its vigorous root growth and active root system under both N conditions. Same root morphological characteristic could not be exhibited by the N‑inefficient cv. Van Gogh. Our study suggested that root morphological characteristics are contributing more than shoot characteristics to N efficiency of potatoes. These traits could be useful characters to breed/select N‑efficient potato rootstocks for sustainable agriculture in the future.

The goal of the present study was to determine whether grafting of watermelon on gourd rootstocks could improve alkalinity tolerance and to investigate the physiological and morphological response mechanisms of the grafted plants under different pH levels. The experiment was carried out in a climate chamber to investigate growth, leaf chlorophyll content (SPAD), leaf area, stem length, shoot and root dry weight, root length, electrolyte leakage, leaf mineral composition, total chlorophyll and carotenoid contents. Two watermelon cultivars (Crimson tide, CT, and Crisby) were grafted onto three commercial Cucurbita maxima × C. moschata hybrid rootstocks under climate-chamber conditions (Strong tosa, ST, Ercole and Nun 9075). The grafted seedlings were transplanted onto 8 L continuously aerated pots containing nutrient solution with two different pH levels (8.5 and 6.5) and replicated three times. The results showed that in both grafted and non-grafted plants, there was a substantial reduction in shoot and root biomass production at high pH levels. At high pH level, the significantly highest leaf area, stem length, SPAD, concentration of P, Ca, S and Mn in leaf tissues were recorded in graft combination ‘Crisby/Ercole’, whereas the significantly highest concentration of Fe in leaf tissues, shoot dry weight were recorded in graft combination ‘Crisby/Nun 9075’. Moreover, at high pH, the significantly highest concentration of Mg and Cu in shoot under high pH levels was significantly found in graft combination of ‘CT/ST’. These results suggest that the use of interspecific Cucurbita maxima × C. moschata hybrid rootstocks can improve crop performance in watermelon plants under alkaline conditions.

In this study, two hydroponic experiments were conducted in nutrient solution growth system. Experiments were conducted in growth chamber of Erciyes University, Agricultural Faculty in Kayseri, Turkey. In the first experiment, 10 local Turkish bottle gourd genotypes and two commercial watermelon cultivars were screened under 2 N doses (0.3 mM and 3.0 mM N) in RBD design with three replications for six weeks. In the second experiment, four genotypes (N-efficient: 70-07 and 07-45, N-inefficient: 35-10 and 45-07) were selected and used as rootstock for grafting with N-inefficient watermelon cultivar (Crimson Sweet) under 2 N doses. The grafted N-efficient gourd genotypes (07-45 and 70-07) significantly contributed to growth and biomass production of the N-inefficient watermelon plants as compared to non-grafted control plants and thus showed a higher rootstock potential for watermelon. The N-efficiency of some gourd genotypes was associated with vigor root growth and active root system particularly at low N conditions. These traits could be useful characters to select ‘N-efficient’ bottle gourd rootstocks for sustainable agriculture in the future.

A hydroponic experiment was conducted to assess whether grafting with Cucurbita rootstocks could improve the salt tolerance of melon scions and to determine the physiological, biochemical, and nutritional responses induced by the rootstocks under salt stress. Two melon (Cucumis melo L.) cultivars (Citirex and Altinbas) were grafted onto two commercial Cucurbita rootstocks (Kardosa and Nun9075). Plants were grown in aerated nutrient solution under deep water culture (DWC) at two electrical conductivity (EC) levels (control at 1.5 dS m−1 and salt at 8.0 dS m−1). Hydroponic salt stress led to a significant reduction in shoot and root growths, leaf area, photosynthetic activity, and leaf chlorophyll and carotenoid contents of both grafted and nongrafted melons. Susceptible plants responded to salt stress by increasing leaf proline and malondialdehyde (MDA), ion leakage, and leaf Na+ and Cl− contents. Statistically significant negative correlations existed between shoot dry biomass production and leaf proline (r = −0.89), leaf MDA (r = −0.85), leaf Na+ (r = −0.90), and leaf (r = 0.63) and root (r = −0.90) ion leakages under salt stress. Nongrafted Citirex tended to be more sensitive to salt stress than Altinbas. The Cucurbita rootstocks (Nun9075 and Kardosa) significantly improved growth and biomass production of grafted melons (scions) by inducing physiological (high leaf area and photosynthesis), biochemical (low leaf proline and MDA), and nutritional (low leaf Na+ and ion leakage and high K+ and Ca++ contents) responses under salt stress. The highest growth performance was exhibited by the Citirex/Nun9075 and Citirex/Kardosa graft combinations. Both Cucurbita cultivars have high rootstock potential for melon, and their significant contributions to salt tolerance were closely associated with inducing physiological and biochemical responses of scions. These traits could be useful for the selection and breeding of salt-tolerant rootstocks for sustainable agriculture in the future.

In this study, pepper (Capsicum annuum L.) inbred lines were grafted onto different rootstock genotypes and tested under saline conditions. A hydroponic experiment was conducted in nutrient solution growth system in a growth chamber of Erciyes University, Agricultural Faculty in Kayseri, Turkey. The experiment was conducted in spring 2017 growth season. Two pepper inbred lines (ERÜ-462 and ERÜ-1227) were grafted onto three different pepper rootstocks/genotypes (Scarface F1, 11B14, and Yaocali F1) and grown in 8 L pots filled with continuously aerated nutrient solution under saline conditions (8 dS m−1) with three replications. The growth chamber experiment was carried out to determine the effects of salt stress on plant growth, shoot and root dry weights, leaf area, photosynthesis, leaf total chlorophyll (a + b) and carotenoid content, proline content, glycine betaine content, leaf electrolyte leakage, leaf and root macro element concentration in grafted and non-grafted pepper plants. The results indicated that ERÜ-462 grafted on to Scarface and 11B14 rootstock genotypes were more tolerant to salinity than ERÜ-1227 in term of leaf chlorophyll (a + b) content and leaf carotenoid content, photosynthesis, and proline content. Though, higher shoot and root biomass, leaf area formation, root K+, Na+, Cl− contents were observed when ERÜ-1227 grafted on to Scarface and 11B14 rootstock genotypes. Strong rootstock promoted plant growth in pepper plant both under control and saline conditions and significant depression of plant biomass production under saline conditions was observed in both grafted and non-grafted plants. However, grafting onto vigorous rootstocks alleviated negative effects of salinity stress on pepper plants. Scarface and 11B14 were found more tolerant to salinity than non-grafted pepper plants and the other genotypes used as regard to investigated parameters.

The genotypic differences in nitrogen (N) utilization efficiency of third backcrossed (BC3) progenies of Sena (Capsicum annuum L.; recurrent parent) and Kopan (Chile penguin; donor parent) pepper plants were determined by examining the changes in the shoot growth at agronomical, root growth at morphological and leaf development at physiological levels under high and low N rates. A hydroponic experiment was conducted by using an aerated deep water culture (DWC) technique in a controlled growth chamber in the spring 2015 growing season. As plant materials, five pepper plants (BC3‑1, BC3‑2, BC3‑3, BC3‑4, BC3-5) were selected from the third backcrossed (BC3) progenies of Sena and Kopan. Plants were grown in 8 L pots filled continuously aerated nutrient solution under at low N (0.5 mM N) and high N (3.0 mM N) rates in randomized complete block design (RCBD) with four replications for 6 weeks. At the experiment plant growth, leaf, shoot and root fresh and dry weights, total leaf area, leaf chlorophyll content (SPAD), total root length, total root volume and average root diameter in pepper plants were assessed. Significant differences in N efficiency were observed between the backcrossed pepper progenies and their respective parents. Leaf, and shoot fresh and dry weights, total leaf area, and leaf chlorophyll content (SPAD) of pepper plants were significantly increased with increasing N rate: 3.0 mM N increased leaf fresh weight by 149.8%, shoot fresh weight by 116.4%, shoot dry weight by 119.6%, total leaf area by 94.54%, and SPAD by 21.28% at BC3‑3 plants as compared to progenies of third backcrosses and their respective parents. Regarding root morphological parameters, pepper plants under high N rate displayed a lower performance than plants under low N rate. Increasing N rate led to a decrease in root fresh weight by 37.96%, and root dry weight by 35.93%. Overall, the N efficiency of the progeny of BC3‑3 was highly associated with vigorous root growth (root fresh and dry weight, total root length and volume) and photosynthetically active leaves (total leaf area, and leaf chlorophyll index) under low N conditions, which could be useful to select and breed “N efficient” pepper varieties.