Impaginato 263 Adv. Hort. Sci., 2019 33(2): 263-270 DOI: 10.13128/ahs-24219 Effects of crop system and genotype on yield, quality, antioxidants and chemical composition of organically grown leek N.A. Golubkina 1 (*), T.M. Seredin 1, M.S. Antoshkina 1, H.V. Baranova 1, V. Stoleru 2, G.C. Teliban 2, G. Caruso 3 1 Agrochemical Research Center, Federal Scientific Center of Vegetable Production, 143072 Moscow Region, Odintsovo District, Vniissok, Selectsionnaya 14, Russia. 2 Department of Horticulture Technology, University of Agriculture Sciences and Veterinary Medicine, 3M Sadoveanu, 700490 Iasi, Romania. 3 Dipartimento di Agraria, Università degli Studi di Napoli Federico II, 80055 Portici, Napoli, Italy. Key words: Allium porrum L., ascorbic acid, greenhouse, mineral elements, polyphenols, sugars. Abstract: The research was carried out in order to assess the effects of nine cul- tivars in factorial combination with open field or greenhouse growing on yield, quality indicators, antioxidants and elemental composition of leek in Moscow region. Greenhouse management resulted in higher yield compared to open field cultivation, due to higher mean pseudo-stem weight, and cultivar Giraffe gave the highest production. Pseudo-stem dry matter was better affected by greenhouse cultivation, whereas the content of monosaccharides, total sugars, nitrates, ascorbic acid and polyphenols was enhanced by open field growing. The cultivars Vesta and Summer breeze showed the highest dry matter and total sugar content, whereas Goliath had the highest antioxidant, selenium and potassium concentration. Among the mineral elements, K and Mg in pseudo- stems were better affected by greenhouse conditions, whereas Ca attained a higher concentration under open field growing. The antioxidant system of Allium porrum was characterized by significant positive correlations between Se, polyphenols, ascorbic acid and potassium. 1. Introduction Leek (Allium porrum L.) is a major crop among Allium species and it is mainly grown in Indonesia, Turkey and, within Europe, in France and Belgium for producing edible pseudo-stems. The latter have high nutri- tional value, also due to the high content of potassium and iron (Koca and Tasci, 2016), and high biological activities connected with the remarkable concentration of antioxidants comparable with that of Allium cepa (*) Corresponding author: segolubkina45@gmail.com Citation: GOLUBKINA N.A., SEREDIN T.M., ANTOSHKINA M.S., BARANOVA H.V., STOLERU V., TELIBAN G.C., CARUSO G., 2019 - Effects of crop system and genotype on yield, quality, antioxidants and che- mical composition of organically grown leek. - Adv. Hort. Sci., 33(2): 263-270 Copyright: © 2019 Golubkina N.A., Seredin T.M., Antoshkina M.S., Baranova H.V., Stoleru V., Teliban G.C., Caruso G. This is an open access, peer reviewed article published by Firenze University Press (http://www.fupress.net/index.php/ahs/) and distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors declare no competing interests. Received for publication 24 September 2018 Accepted for publication 25 February 2019 AHS Advances in Horticultural Science http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ Adv. Hort. Sci., 2019 33(2): 263-270 264 (Sekara et al., 2017), such as polyphenols (Ben Arfa et al., 2015), glucosinolates, S-alkenyl-L-cysteine sulfox- ides and pectic polysaccharides (Ozgur et al., 2011). Accordingly, leek shows antimicrobial, cardio-protec- t i v e , h y p o - c h o l e s t e r e m i c , h y p o g l y c e m i c , a n t i - rheumatic, hypotensive, antianemia, and anticancer action, improves liver, gastro-intestinal and brain e f f i c i e n c y , d e c r e a s e s b l o o d p r e s s u r e , i n h i b i t s platelets aggregation and prevents neural tube defects as well as prostate diseases (Radovanović et al., 2015). Protected cultivation may be appropriate to organic horticulture which is more susceptible to the environmental unbalances due to the milder farming practices and is usually more profitable than the con- ventional management (Caruso et al., 2012; Conti et al., 2015). Within the crop system, cultivar assess- ment in terms of content of antioxidants as well as macro- and micro-elements in leek pseudo-stems raises the interest of establishing the relations between the mentioned substances and, accordingly, identifying the most interesting genotypes, also based on their yield. Due to the fragmented investi- gations relevant to varietal differences in biologically active compounds (Bernaert et al., 2012) and ele- mental composition (Koca and Tasci, 2016), we car- ried out research aiming to evaluate the effect of both crop system and cultivar on yield, quality, antioxidant content and elemental composition of A. porrum grown either in greenhouse or in open field. 2. Materials and Methods Plant material and growth conditions Research was carried out on leek (A. porrum L.) grown in greenhouse at the experimental fields of Federal Scientific Center of Vegetable Production, in Odintsovo (Moscow, Russia, 55°40’ N, 37°12’ E) in 2015 and 2016 on a clay-loam soil, with рН 6.8, 2.1% organic matter, 108 mg kg-1 N, 450 mg kg-1 P2O5, 357 mg kg-1 K2O, exchangeable bases sum as much as 95.2%. Mean temperature values from May to October were: 13.0, 16.1, 19.8, 18.6, 12.3, 6.4°C in open field; 20.4, 21.4, 23.7, 20.0, 14.5, 8.3 in green- house. The experimental protocol was based on the factorial combination between two crop systems (open field, greenhouse) and nine cultivars (Goliath, Summer breeze, Premier, Casimir, Kalambus, Camus, Vesta, Giraffe, Bandit), using a split-plot design with three replicates. The sowing was performed on 5 December in 8 x 8 cm trays and the plantlets were transplanted in the field on 14 May, spaced 15 cm along the rows, the latter being 40 cm apart. Leek crops were preceded by organically grown vegetables in the previous four years, such as carrot, bean, rape and pea. Prior to planting, plough at 30 cm depth, hoeing at 15 cm and fertilization with 180 kg ha-1 N, 80 P2O5 and 120 K2O were practiced; during the growing period, 40 kg ha-1 N were supplied in three times at two-week intervals, starting at bulbification stage, and just in the last N application 7 kg ha-1 of P2O5 and of K2O were also provided. Drip irrigation was activated at 80% soil available water. The organic farming practice com- plied with EC Regulation 834/2007 and 889/2008. Plant protection was achieved by applying copper oxychloride against rust and azadirachtin against aphids. Harvests of ripe plants were performed from 5 to 10 October in greenhouse and from 12 to 19 October in open field, when the pseudo-stems had reached their maximum growth, and the leaf blades were trimmed at 15 cm length for obtaining the mar- ketable product. In each plot, determinations were made of the marketable product weight (pseudo- stems with 15 cm long leaf blades) and the mean pseudo-stem (with 15 cm long leaf blades) weight on twenty-plant samples. Further plant samples were collected, gently washed with water to remove sur- face contaminants and dried with filter paper. Pseudo-stems and leaves were separated, cut with plastic knife, dried to constant weight and homoge- nized; the resulting powders were subjected to labo- ratory analysis. Dry matter The dry matter content in leaves and pseudo- stems of A. porrum was assessed after dehydration of the fresh samples in an oven at 70°C, until they reached constant weight. Sugars Monosaccharides were determined using ferri- cyanide colorimetric method, based on the reaction of monosaccharides with potassium ferricyanide (Swamy, 2008). Total sugars were determined after a c i d i c h y d r o l y s i s o f w a t e r e x t r a c t s w i t h 2 0 % hydrochloric acid (Swamy, 2008). Fructose was used as an external standard. Polyphenols The concentrations of the total polyphenols in each sample of leaves and pseudo-stems were deter- mined in 70% ethanol extract (1 hour at 80oC) using the Folin-Ciocalteu colorimetric method, according to Golubkina et al. - Crop system and genotype effects in Allium porrum 265 Golubkina et al. (2018 b) by Unico 2804 UV (USA) spectrophotometer. The polyphenol content was expressed as milligrams of gallic acid equivalents per 100 grams of dry weight (mg GAE 100 g-1 d.w.). Ascorbic acid The ascorbic acid content in leek leaves and pseu- do-stems was assessed by visual titration of fresh plant extracts in 6% trichloracetic acid with Tillmans reagent (Caruso et al., 2009; AOAC, 2012). Antioxidant activity The antioxidant activity of leek leaves and pseu- do-stems was assessed using redox titration method (Maximova et al., 2001; Golubkina et al., 2018 b), via titration of 0.01 N KMnO 4 solution with ethanolic extracts of leaves and pseudo-stems. The values were expressed in mg GAE 100 g-1 d.w. Nitrates The nitrate content was assessed in fresh pseudo- stems using ion selective electrode on ionomer Expert-001 (Econix, Russia). Elemental composition The content of Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, I, K, Li, Mg, Mn, Na, Ni, P, Pb, Se, Si, Sr, V and Zn in leek pseudo-stems was assessed using ICP-MS on quadru- ple mass-spectrometer Nexion 300D (Perkin Elmer Inc., Shelton, CT 06484, USA) in the Biotic Medicine Center in Moscow (Golubkina et al., 2017). Statistical analysis Data were processed by analysis of variance and mean separations were performed through the Duncan multiple range test, with reference to 0.05 probability level, using SPSS software version 21. The data expressed as a percentage were subjected to angular transformation before processing. As the year of research had no significant effect on the yield, quality, antioxidant and elemental com- position variables examined, both as main factor or in interaction with the experimental factors “crop system” and “cultivar”, the results are reported as average values of the two years of investigation. 3. Results and Discussion Growth, yield and quality indicators of pseudo-stems The crop system showed significant effects on leek plant biomass, pseudo-stem yield and mean weight, as these variables attained higher values in greenhouse compared to open field (Table 1); as reported in the previous section, the plant commer- cial ripeness was anticipated by 8 days on average in the protected environment. These trends are consis- tent with those recorded in previous research (Conti et al., 2015). Differences between the varieties were recorded with regard to: biomass, which was highest in cultivar Summer breeze and lowest in Premier; mean pseudo-stem weight and, accordingly, yield which ranged from 22.0 to 36.1 Mg ha-1, with the cul- tivar Giraffe showing the best performance, Premier and Kalambus the worst. The greenhouse growing resulted in higher con- centration of dry matter, ash and nitrates, but lower monosaccharides and total sugars in pseudo-stems, compared to those detected in open field (Table 1), similarly to previous reports (Conti et al., 2015). Notably, the values of dry matter recorded in our Table 1 - Growth and yield indicators, and content of dry matter, sugars and nitrates in A. porrum pseudo-stems * significant at P≤0.05. Within each column, means followed by different letters are significantly different according to Duncan test at P≤0.05. Treatment Plant biomass (Kg m-2 d.w.) Marketable pseudo-stems Yield (Mg ha-1) Mean weight (g) Dry matter (%) Monosaccharides (g 100 g-1 d.w.) Total sugars (g 100 g-1 d.w.) Ash (%) Nitrates (mg kg-1 f.w.) Crop system Open field 11.0 25.3 162.8 16.7 3.81 12.0 4.8 44.7 Greenhouse 15.8 30.8 185.7 19.7 3.41 10.7 5.2 66.3 * * * * * * * * Cultivar Goliath 8.7 ef 27.6 de 177.0 de 12.1 e 5.11 a 7.5 e 8.5 b 48.0 d Premier 8.3 f 22.0 g 132.6 g 14.6 d 4.62 ab 10.6 c 12.4 a 45.9 d Bandit 12.0 d 31.0 bc 192.8 bc 14.9 d 3.73 c 8.9 d 4.7 c 65.3 a Kalambus 9.9 e 22.3 g 134.6 g 17.1 c 4.13 bc 10.5 c 2.8 e 43.1 d Cazimir 11.6 d 24.3 f 150.1 f 18.4 c 2.98 d 11.0 bc 4.1 cd 57.5 bc Giraffe 18.6 b 36.1 a 225.4 a 19.8 b 3.58 c 11.2 bc 3.1 e 54.7 c Camus 16.0 c 29.9 cd 188.0 cd 20.6 b 2.62 d 12.3 b 3.2 e 64.9 a Vesta 15.4 c 26.3 ef 163.8 ef 22.6 a 2.74 d 14.6 a 2.9 e 60.1 ab Summer breeze 20.3 a 33.1 b 204.5 b 23.7 a 2.97 d 15.5 a 3.4 de 60.5 ab Adv. Hort. Sci., 2019 33(2): 263-270 266 research fell within the 12.1 to 23.7 % range (Table 1) which is much wider than that relevant to A. porrum grown in Czech Republic (9-11%) (Lundegardh et al., 2008). Moreover, the cultivars with high dry matter content (Summer breeze and Vesta) have a long shelf-life and are even suitable as dry spice source, w h er ea s t h e v a r i et i es s h o w i n g l o w d r y m a t t er (Goliath, Premier and Bandit) better fit the salad industry target. Significant varietal differences in ash content were recorded (Table 2), with the ratio between leaf and pseudo-stem related to this variable decreasing as follows: Summer breeze > Cazimir > Vesta > Giraffe > Bandit > Kalambus > Camus > Premier > Goliath. The higher nitrate accumulation in pseudo-stems grown in greenhouse is connected with the lower light intensity occurring in the protected environ- ment compared to open field conditions, which limits the nitrate reductase activity; however, it was much lower (105 mg kg-1 f.w.) than that relevant to the top- a c c u m u l a t o r s p e c i e s ( C a r u s o e t a l . , 2 0 1 1 ) a n d referred to previous reports (Santamaria, 2006). Antioxidants Ascorbic acid and polyphenols highly affect plant antioxidant activity (Proteggente et al., 2002); in our research, the open field conditions resulted in higher content of both antioxidant compounds in leek pseu- do-stems compared to greenhouse (Table 2). The crop system did not affect the selenium concentra- tion either in pseudo-stems or leaves of A. porrum. The high average content of ascorbic acid record- ed in our research presumably makes the product safe and healthy, as ascorbic acid participates in pro- ducing essential nitrogen oxide for human organism, thus preventing nitrosamine formation from nitrate a c c u m u l a t i n g i n p l a n t s ( S a n t a m a r i a , 2 0 0 6 ) . Moreover, wide varietal differences were found in ascorbic acid concentration, unlike the polyphenol content which was characterized by higher stability in pseudo-stems and even more in leaves (Table 2). Among the cultivars examined, Goliath showed the highest content of ascorbic acid, polyphenols and selenium in pseudo-stems (Table 2). Notably, these cultivars from domestic selection are characterized by lower levels of polyphenols compared to litera- ture references, which may be connected with the different crop cycle and harvest time (Biesiada et al., 2007). Bernaert et al. (2012) also reported a higher polyphenol concentration in pseudo-stems of thirty leek cultivars grown in Belgium (7.3 to 11.3 mg GA g-1 d.w.) compared to our values (3.3 to 6.3), but a lower content of ascorbic acid ranging between 90 to 350 mg 100 g-1 d.w. In the latter research no correlation was recorded between ascorbic acid and polyphenol concentration in leek pseudo-stems, whereas a significant positive relationship has been found in our investigation (r = 0.94 at P<0.01). The lack of correlation relevant to the thirty leek cultivars grown in Belgium (Bernaert et al., 2012) presumably depends on varietal hetero- NS not significant; * significant at P≤0.05. Within each column, means followed by different letters are significantly different according to Duncan test at P≤0.05. Table 2 - Concentrations of ascorbic acid, polyphenols and selenium in leek Treatment Ascorbic acid in pseudo-stems (mg 100 g-1 f.w.) Polyphenols (mg GA 100 g-1 d.w.) Selenium (µg kg-1 d.w.) Pseudo-stems Leaves Pseudo-stems Leaves Crop system Open field 57.6 466.5 887.1 71.9 61.2 Greenhouse 47.2 376.8 699.5 76.2 64.4 * * * NS NS Cultivar Goliath 169.3 a 626.1 a 827.8 a 106.4a 14.1 e Premier 72 b 497.6 b 751.8 b 79.1 b 64.8 c Bandit 50.6 c 455.6 bc 739.8 b 74.1 bc 47.2 d Kalambus 32.1 de 368.6 de 858.5 а 70.6 bc 74.8 b Cazimir 37 d 334.1 e 843.1 а 59.7 e 76.9 ab Giraffe 31.3 ef 386.1 d 760.8 аb 72.9 bc 48.4 d Camus 27.1 fg 401.6 cd 786.3 ab 63.1 de 81.4 ab Vesta 24.3 g 345.3 de 855.5 a 68.1 cd 85.4 a Summer breeze 28.0 fg 379.7 de 716.3 b 72.1 bc 72.3 bc Golubkina et al. - Crop system and genotype effects in Allium porrum 267 tion between selenium and polyphenol content was found in wheat (Lachman et al., 2011) and a negative correlation between quercetin and selenium was recorded in A. cepa (Golubkina et al., 2016). However, moderate doses of selenium are deemed to enhance the content of antioxidants such as polyphenols, flavonoids and carotenoids (Malagoli et al., 2015). In our research, the nine leek genotypes examined showed significant correlations between the compo- nents of the antioxidant system, i.e. selenium, ascor- bic acid and polyphenols: Se and ascorbic acid (r= 0.93 at P≤0.01); Se and polyphenols (r= 0.92 at P≤0.01); ascorbic acid and polyphenols (r = 0.94 at P≤0.01). The latter correlations relevant to leek pseu- do-stems may be significantly useful in leek selection based on high antioxidant content. Elemental composition The beneficial effect of many mineral elements to human health has arisen a remarkable interest to the chemical composition of vegetable crops, such as leek (Koca and Tasci, 2016). Investigations of element content in A. porrum plants have disclosed this species ability to accumulate high concentrations of minerals, but so far assessments of the leek whole profile relevant to mineral elements and to the vari- etal features connected to their accumulation have been lacking. The analysis of twenty-five element content in leek pseudo-stems (Tables 3-5) has allowed to assess the varietal differences in elemental profile. The con- centration of calcium was higher in pseudo-stems grown in greenhouse, whereas potassium and mag- nesium attained higher levels in open field. Sodium, geneity, consequent to genotype selection based on morphological types (light-green summer type, dark- green winter type and intermediate autumn type). Interestingly, in our research the concentration of polyphenols in leek leaves has always been higher than the pseudo-stem one, raising the issue of possi- ble crop waste valorization as a source of these antioxidants. Among the components of plant antioxidant sys- tem, selenium also plays a significant role. Indeed, though it is not an essential element for plants, sele- nium is able to provide a powerful antioxidant defense to plants against drought, salinity, frost, flooding, UV light and herbivore (Malagoli et al., 2015). Notably, Allium species belong to the sec- o n d a r y s e l e n i u m a c c u m u l a t o r s , w h i c h s h o w a remarkable tolerance to high concentration and con- sequent accumulation of this element due to Se abili- ty to substitute sulfur in natural compounds, as previ- ously reported in leek (Koca and Tasci, 2016). In our research, A. porrum grown in Moscow region showed a Se accumulation range from 60 to 107 µg kg- 1 d.w., which is much lower than the values recorded in Turkey (Koca and Tasci, 2016). This suggests the sig- nificant effect of selenium status in the environment on plant ability to concentrate this microelement. The adverse correlation between selenium content in leaves and pseudo-stems (r= - 0.95 at P≤0.01), similar to that recorded for polyphenols, entails a rather sta- ble level of selenium accumulation in plant. Reports relevant to selenium in plant secondary metabolites, as well as to polyphenols particularly in absence of selenium uptake are rather scarce and often controversial. In this respect, a positive correla- Table 3 - Macroelement concentration in A. porrum pseudo-stems (g kg-1 d.w.) NS not significant; * significant at P≤0.05. Within each column, means followed by different letters are significantly different according to Duncan test at P≤0.05. Treatment Calcium Potassium Magnesium Sodium Phosphorus Crop system Open field 4.2 22.5 1.0 0.27 2.83 Greenhouse 4.8 18.9 0.8 0.28 2.73 * * * NS NS Cultivar Goliath 3.7 bc 58.7 a 0.8 c 0.32 bc 3.12 b Premier 3.1 cd 5.4 e 0.8 c 0.36 b 2.74 bc Bandit 10.4 a 26.3 b 2.1 a 0.75 a 2.53 cd Kalambus 4.0 b 15.2 c 0.6 d 0.16 e 2.43 cd Cazimir 4.3 b 9.0 d 0.6 d 0.15 e 2.08 d Giraffe 2.6 d 17.9 c 0.7 cd 0.12 e 2.49 cd Camus 4.4 b 19.6 c 1.1 b 0.16 e 4.07 a Vesta 3.9 bc 16.9 c 0.7 cd 0.18 de 2.77 bc Summer breeze 4.4 b 17.7 c 0.8 c 0.26 cd 2.80 bc 268 Adv. Hort. Sci., 2019 33(2): 263-270 phosphorus and all the microelements and heavy metals analyzed were not significantly affected by the crop system (Tables 3-5). Moreover, the potassi- um concentration was positively correlated with the ash content (r= 0.78 at P≤0.01). From the comparison between the nine leek culti- vars it arose that the three cultivars Premier, Goliath and Cazimir had contrasting features from each other. Indeed, Goliath was characterized by the high- est content of K, Fe, B, Zn and Se, and the lowest of Cd. Premier accumulated preferably Со, I, Al, As, Cd, Ni, Pb and Sr, but poorly Cu and Zn. Cazimir showed the highest concentration of Na and Zn, but the low- est of K, I, Se, Cr and Ni. Among the minerals examined, the highest corre- lation coefficients were recorded between Al and As, Pb, V, Со and Li. Indeed, the physiological role of Al in plants has not been completely understood so far, though this element is supposed to both activate at low doses some enzymes and control membrane per- meability (Ahn and Matsumoto, 2006). Lithium also showed wide varietal differences, consistently with previous reports (Kabata-Pendias and Pendias, 2010). The correlations recorded in our research are in agreement with those found in five species grown both in ecological unpolluted and in oil-polluted areas of Nigeria (Essiett et al., 2010). As for selenium, though the leek varietal differences are rather low compared to other elements, the signifi- cant correlation recorded between Se and K is a remarkable characteristic of this Allium species and it has been very scarcely investigated so far. In spinach, the fertilization with sodium selenate increased the potassium content in the female plants but not in the male ones (Golubkina et al., 2017), whereas in other research (Põldma et al., 2011) garlic biofortification led to selenium antagonistic activity towards K. Taking into account that potassium partic- ipates in plant protection against all forms of biotic and abiotic stress along with selenium and other antioxidant compounds (Wang et al., 2013), the close relationship between the two minerals in leek sug- gests intensive interactions between all components of the defense system. Indeed, potassium was pre- dominant in leek elemental composition, showing significant correlations with both ash (r= 0.78 at P≤0.01) and polyphenols (r= 0.96 at P≤0.01). The known ability of potassium to decrease the activity of polyphenol oxidase in plants and enhance polyphe- nol accumulation (Mudau et al., 2007) may be a good explanation of the positive correlation between polyphenols and potassium in leek plants. The active Table 4 - Microelements concentration in A. porrum pseudo-stems (mg kg-1 d.w.) Table 5 - Heavy metal concentration in A. porrum pseudo-stems (mg kg-1 d.w.) Within each row, means followed by different letters are significantly different according to Duncan test at P≤0.05. Within each row, means followed by different letters are significantly different according to Duncan test at P≤0.05. Element Goliath Cazimir Premier Vesta Kalambus Summer breeze Bandit Giraffe Camus B 20.5 a 14.8 bc 16.3 b 9.5 de 8.5 e 9.4 de 9.4 de 12.3 cd 10.7 d Co 0.08 b 0.05 d 0.10 b 0.03 d 0.29 a 0.04 d 0.04 d 0.04 d 0.10 b Cu 4.7 df 4.4 ef 3.4 g 5.7 bc 6.4 ab 5.0 ce 6.8 a 4.0 fg 5.3 cd Fe 206 a 110 c 168 b 97 bd 74 e 80 de 93 ce 100 cd 215 a I 0.06 bc 0.04 c 0.31 a 0.04 c 0.06 bc 0.06 bc 0.04 c 0.08 b 0.08 b Li 0.11 b 0.04 c 0.15 a 0.03 c 0.01 c 0.03 c 0.02 c 0.03 c 0.11 b Mn 12.2 c 12.0 c 22.6 a 9.8 c 6.3 d 9.5 c 10.6 c 19.2 b 21.7 ab Si 14.1c 10.5 d 27.3 a 9.2 e 12.8 cd 13.1 cd 11.0 de 18.8 b 15.4 c Sn 0.15 c 0.22 b 0.02 d 0.16 c 0.48 a 0.18 bc 0.51 a 0.22 b 0.23 b Zn 23.5 ab 26.7 a 11.8 f 18.1 de 16.0 e 19.2 ce 21.5 bc 22.2 bc 21.2 bd Element Goliath Cazimir Premier Vesta Kalambus Summer bree- ze Bandit Giraffe Camus Al 78.0 c 29.5 d 126.0 a 21.0 df 7.7 g 24.1 de 12.2 fg 19.3 ef 88.4 b As 0.03 b 0.02 bc 0.05 a 0.02 bc 0.01 c 0.02 bc 0.01 c 0.02 bc 0.06 a Cd 0.08 d 0.10 bc 0.18 a 0.11 b 0.08 d 0.06 d 0.11 b 0.17 a 0.11 b Cr 0.13 c 0.08 g 0.48 a 0.10 df 0.10 eg 0.12 cd 0.09 fg 0.15 b 0.11 ce Ni 1.05 a 0.46 c 0.96 ab 0.98 ab 0.56 c 0.57 c 0.83 b 0.60 c 1.08 a Pb 0.34 b 0.28 bc 0.83 a 0.10 e 0.10 e 0.13 de 0.20 cd 0.12 e 0.83 a Sr 28.3 ab 25.3 c 30.4 a 24.6 c 28.2 ab 17.3 d 28.8 ab 26.4 bc 28.5 ab V 0.21 b 0.07 cd 0.28 a 0.07 cd 0.04 d 0.09 c 0.07 cd 0.07 cd 0.30 a Golubkina et al. - Crop system and genotype effects in Allium porrum 269 participation of potassium in the antioxidant defense system of this Allium species is also characterized by positive correlation of the element with the ascorbic acid content (r= 0.95 at P≤0.01). In this respect, the results of the present work reveal the close relation- ship between the main components of the leek antioxidant system, including polyphenols, ascorbic acid, selenium and potassium. In our research, the lowest negative correlation coefficients were recorded between selenium, chromium and iodine (Table 6). Se is known as an antagonist of Cr and its protective role towards Cr has been previously reported (qing et al., 2015). The interaction between Se and I is more complex; both the elements are not essential for plants, but at low concentrations they may improve plant growth, development and protection from biotic and abiotic stresses (Pilon-Smits, 2015). Separate plant fortifica- tion with Se and I showed the possibility of mutual stimulation by the two elements (Golubkina et al., 2018 a). The selective accumulation of selenium in the spinach male plants and of iodine in the female ones suggests the participation of phytohormones in the interactions between selenium and iodine (Golubkina et al., 2017). With regard to heavy metals, highly significant correlations were found between V and Al, As, Со, Pb and Fe (Table 6). 4. Conclusions From research carried out in Moscow region with the aim to assess the effects of open field or green- house conditions on yield and quality performances of nine leek (A. porrum) cultivars under organic farm- ing, useful remarks have been drawn. The genotypes examined had a uniform behavior with both the crop systems, showing higher yield and dry matter when grown in the protected environment, but better qual- ity and antioxidant performances in the open field conditions. 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