Phytochemical composition and antioxidant activity of high-lycopene tomato (Solanum lycopersicum L.) cultivars grown in Southern Italy

In this study, the antioxidant components and of six high-lycopene (Lyco 1, Lyco 2, HLY 02, HLY 13, HLY 18 and Kalvert) and one ordinary (Donald) tomato cultivars (cvs) grown simultaneously in an open-field of the Southern Italy were investigated. Lycopene, β-carotene, lutein, total phenols, flavonoids, ascorbic acid (AsA), dehydroascorbic acid (DHA) and total vitamin C (AsA + DHA) contents, as well as hydrophilic and lipophilic antioxidant activities (HAA and LAA) were determined. Significant differences were detected among tomato cvs in all studied antioxidant components, as well as in the antioxidant activity of their hydrophilic and lipophilic fractions. High-lycopene tomato cvs showed higher lycopene, β-carotene, HAA and LAA when compared to cv Donald. Cv HLY 18 showed the highest lycopene and β-carotene content with 232.9 mg/kg fresh weight (fw) and 19.4 mg/kg fw, respectively. Except for Kalvert, high-lycopene tomato cvs also obtained higher total vitamin C levels, with cv HLY 13 top ranking with an average of 352.8 mg/kg fw. LAA ranged from 133.5 μM Trolox/100 g fw in cv Donald to 540.1 μM Trolox/100 g fw in cv Lyco 2 and was significantly correlated to lycopene (r = 0.53; p < 0.01) and β-carotene (r = 0.56; p < 0.01) contents. A variation between 2.7- and 4.0-fold was found in LAA of high-lycopene tomato cvs compared to Donald. HAA was significantly correlated to the amount of DHA (r = 0.61; p < 0.01) and total vitamin C (r = 0.60; p < 0.01). Although these data require confirmation over a longer period of time, this investigation suggests a promising use of the high-lycopene tomato cvs for the production of tomatoes with higher nutritional quality.     

Fruit yield and water use efficiency of eggplant (Solanum melongema L.) as influenced by different quantities of nitrogen and water applied through drip and furrow irrigation

Elucidation of the effects of different quantities of nitrogen (N) and water applied through drip and furrow irrigation on fruit yield and water use efficiency (WUE) in eggplant is essential for formulating proper management practices for sustainable production. The present investigation was undertaken to evaluate the independent and interactive effects of four levels of N and different quantities of water applied through drip as well as furrow irrigation on eggplant fruit yield, agronomic efficiency of N and WUE. In the present field investigation, ridge planting with each furrow and alternate furrow irrigation were compared with drip irrigation at three levels of water: 100%, 75% and 50% of each furrow irrigation (designated as D_1.0, D_0.75 and D_0.5). The four levels of N studied were 90, 120, 150 and 180 kg N ha⁻¹ (designated as N₉₀, N₁₂₀, N₁₅₀ and N₁₈₀). The eggplant hybrid BH-1 was transplanted on August 5, 2004 at the spacing of 60 cm × 45 cm.     

Assessment of genetic purity of tomato (Lycopersicon esculentum L.) hybrid using molecular markers

Three DNA molecular marker systems, RAPD, ISSR and SSR, were used to test seed genetic purity of two commercial hybrid tomato (Lycopersicon esculentum L.) cultivars ‘Hezuo 903’ and ‘Sufen No. 8’. Genomic DNA from the two F₁ hybrid cultivars and their corresponding parental lines was screened with 218 RAPD decamer primers, 54 ISSR primers and 49 SSR primers. Among the 321 primers, 4 primers for ‘Hezuo 903’ and 3 for ‘Sufen No. 8’, which could produce both female and male parent-specific markers, were selected for testing the genetic purity. A total of 210 hybrid individuals of each cultivar were analyzed using the identified primers. The combined results of the marker analysis showed that eight of the 210 F₁ plants in ‘Hezuo 903’ and 13 of 210 in ‘Sufen No. 8’ were false hybrids, and the overall genetic purity of the two F₁ hybrid seed lots was 96.2 and 93.8%, respectively. This study showed that RAPD and SSR markers could provide a practical and efficient tool in quality control of the tomato commercial hybrid seeds.     

A comparison of nitrogen use efficiency definitions in Citrus rootstocks

Nitrogen use efficiency (NUE) definitions, commonly used in literature, are evaluated in response to nitrate availability in four citrus rootstocks, Rough Lemon (Citrus jambhiri Lush) (RL), Sweet Orange (Citrus sinensis (L.) Osbeck) (SwO), Cleopatra Mandarin (Citrus reshni Hort ex Tan.) (CM) and Sour Orange (Citrus aurantium L.) (SO). The application of diverse definitions determine different characterizations in N-efficiency among rootstocks. Nitrogen utilization efficiency (NUtE) and nitrogen efficiency ratio (NER) determine equal level of nitrogen efficiency among all rootstocks. Total nitrogen accumulation (TNA), nitrogen uptake efficiency (NUpE), shoot dry weight (SDW) and total leaf area (TLA) response curves produce the same NUE characterization: SO and SwO were nitrate use efficient and inefficient rootstocks, respectively, while the RL and CM exhibit superior and inferior genetic potential, respectively.     

Effect of different fertilisation and irrigation practices on yield,nitrogen uptake and fertiliser use efficiency of white cabbage (Brassica oleracea var. capitata L.)

The effect of different fertilisation (i.e. broadcast application and fertigation) and irrigation practices (tank sprinkler and drip irrigation) on yield, yield quality (nitrate content), nitrogen uptake of white cabbage (Brassica oleracea var. capitata L.) and the potential for N losses was assessed on sandy-loam agricultural soil. ¹⁵N-labelled fertiliser was used as a tracer. It was found that different practices significantly affected yield, nitrate content in plants, N uptake, as well as fertiliser use efficiency. The highest yield (93 t ha⁻¹), plant N uptake (246 kg ha⁻¹), and fertiliser use efficiency (42%) were obtained under treatment with broadcast fertilisation with farmer's practice of irrigation (tank sprinkler). The N surplus after harvest was −41 kg N ha⁻¹, indicating the lowest potential for N losses. Treatment by fertigation and drip irrigation covering 100% of the crop's water requirements did not result in the highest yield as expected (72 t ha⁻¹), the N surplus after harvest was about +38 kg ha⁻¹. The lowest yield (58 t ha⁻¹), fertiliser use efficiency (30%) and hence the highest potential for N losses (N surplus after harvest +68 kg ha⁻¹) were found in treatment with broadcast fertilisation and drip irrigation covering 50% of the crop's water requirements.     

Translocation of heavy metals to tomato (Solanum lycopersicom L.) fruit irrigated with treated wastewater

A field experiment was conducted to investigate the extent of translocation of heavy metals to tomato (Solanum lycopersicom L. cvs. “GS₁₂” and “RS₅₈₉₉₅₆”) fruit produced in an open field near to Abu-Nusiar Wastewater Treatment Plant, Amman-Jordan. Seedlings were planted during the seasons of 1999 and 2000 and furrow irrigated with different mixtures of potable water to treated wastewater {100%:0% (1:0, control); 25%:75% (1:3); 50%:50% (1:1); 0%:100% (0:1)}. Tomato fruit, soil and water were examine for heavy metals concentrations, and changes in the pH and electrical conductivity (EC) of the soil were tested. The obtained results revealed an increase in the concentrations of Cu, Mn and Fe, in the soil correlated with high concentrations found in the wastewater. Additionally, an increase in the pH and EC in the soil was observed with increasing the proportions of wastewater. Results of tomato fruit analysis showed an increased concentration of Fe, Cu, Ni, Mn and Zn in the cultivar “RS₅₈₉₉₅₆”, whereas, an increased concentration of Mn and Zn were detected in the cultivar “GS₁₂”, but no accumulation of Cd and Pb in both cultivars. The accumulation of heavy metals in fruit was below the Jordanian standard limits, thus, the use of treated wastewater in irrigation might be feasible.     

ISSR variations in eggplant (Solanum melongena L.) and related Solanum species

Inter-simple sequence repeat (ISSR) analysis was performed in eight cultivars of eggplant (Solanum melongena) and 12 accessions in eight related Solanum species to evaluate the applicability of this analysis for assessing the phylogenetic relationships and identifying cultivars. A total of 552 polymorphic amplified bands were obtained from 34 of the 100 primers tested, and the percentage of polymorphisms was 99.1%. Cluster analysis based on the ISSR markers classified the Solanum species into seven groups: (i) S. melongena; (ii) S. aethiopicum and S. anguivi; (iii) S. incanum; (iv) S. violaceum and S. kurzii; (v) S. macrocarpon; (vi) S. virginianum and (vii) S. torvum. Combining the ISSR markers obtained by a few of the 34 primers was enough for distinguishing of the eight cultivars of eggplant. This ISSR analysis was demonstrated to be available for the phylogenetic study and the cultivar identification.     

Estimated nitrogen use efficiency,surplus, and partitioning in young apple trees grown in varied organic production systems

A certified organic apple (Malus × domestica Borkh.) orchard was established to study the interaction of ground cover management systems (GMS) and nutrient sources (NS) on nitrogen (N) use efficiency and N surplus in the Southern U.S. for three years. Trees treated with green compost (GC) and wood chips (WC), regardless of the NS, had greater N accumulation and leaf N use efficiency compared to the shredded paper or mow-and-blow treated trees. The WC-treated trees had comparably low N surplus relative to the GC trees that induced more [NO₃⁻] in soil or soil solution in the rooting zone in September in year 3. GC trees had the highest [NO₃⁻] mineralization in the soil during winter. GMS had greater overall effects on the tree response variables than did the NS.     

Effects of greenhouse cooling method on growth,fruit yield and quality of tomato (Solanum lycopersicum L.) in a tropical climate

A tomato (Solanum lycopersicum L.) crop was grown in four greenhouses during the dry season 2005/06 in Central Thailand. Sidewalls and roof vents of two greenhouses were covered with nets and these greenhouses were mechanically ventilated when air temperature exceeded 30 °C (NET). The other two greenhouses were covered with polyethylene film and equipped with a fan and pad cooling system (EVAP). Overall mean air temperature was significantly reduced by 2.6 and 3.2 °C (day) and 1.2 and 2.3 °C (night) in EVAP as compared to NET and outside air, respectively. Temperature maxima in EVAP averaged about 4 °C lower than in NET and outside. The relative humidity was around 20 and 30% (day) and 10 and 15% (night) higher in EVAP than in NET or outside, respectively. Vapour pressure deficit averaged 0.25 kPa in EVAP, 1.03 kPa in NET and 1.48 kPa outside. The crop water-consumption was significantly lower in EVAP (1.2) than in NET (1.8 L plant⁻¹ day⁻¹), which is ascribed to reduced transpiration in EVAP. Total fruit yield was similar in NET (6.4 kg plant⁻¹) and EVAP (6.3 kg plant⁻¹). The quantity of undersized (mostly parthenocarpic) and blossom-end rot (BER)-affected fruits was reduced in EVAP. However, the proportion of marketable yield was significantly higher in NET (4.5 kg plant⁻¹) than in EVAP (3.8 kg plant⁻¹), owing largely to an increased incidence of fruit cracking (FC) in EVAP. Higher FC but lower BER incidence coincided with higher fresh weight and Ca concentration in the fruits in EVAP. It is concluded that in regions with high atmospheric relative humidity evaporative cooling without technical modifications allowing dehumidification will not improve protected tomato production.     

The insertion of the Agrobacterium rhizogenes rolC gene in tomato (Solanum lycopersicum L.) affects plant architecture and endogenous auxin and abscisic acid levels

In the present paper we report on the effects of the insertion of the Agrobacterium rhizogenes rolC gene in the tomato (Solanum lycopersicum L., formerly Lycopersicon esculentum Mill.) cultivar Tondino. Several transgenic lines were successfully obtained, between which two clones, rolC1 and rolC3, were chosen for the analysis of morpho-productive traits as well as of the endogenous levels of auxin and abscisic acid. Consistent with the known phenotypic effect of this gene, the transformed tomato plants were significantly shorter than the corresponding controls. On the other hand, even if yield was not affected by the transformation in terms of average number of fruits produced, fruit weight was significantly lower in the transgenics with respect to the controls. Therefore, insertion of the rolC gene does not lead to an improvement in plant productivity.     

Effect of partial rootzone drying on growth, gas exchange, and yield of tomato (Solanum lycopersicum L.)

Three levels of partial rootzone drying (PRD) were evaluated and compared with conventional irrigation, in terms of gas exchange, water relations, growth, yield, fruit quality, and water use efficiency in tomato (Solanum lycopersicum L.) saladette-type plants growing in pots with volcanic material and drip irrigation. There were four treatments, a control, in which available water (AW) in the whole root system was allowed to fall to 90%; PRD90-30, in which on one side of the divided root AW was allowed to fall to 90% and on the other side it was allowed to fall to 30%; PRD70-30, in which on one side of the divided root AW was allowed to fall to 70% and on the other side it was allowed to fall to 30%; PRD50-30, in which on one side of the divided root AW was allowed to fall to 50% and on the other side it was allowed to fall to 30%. When each treatment reached the desired AW level they were then irrigated. At the same time, when on one side AW reached values ≤30% irrigation was shifted to the other side. Results showed a significant decrease of leaf water potential up to 14% in PRD plants compared with control. Shoot dry weight and leaf area decreased in relation to substrate available water in PRD plants. Stomatal conductance and transpiration rate were lower, up to 31 and 18%, respectively, in plants with PRD compared with control. However, CO₂ assimilation rate was similar among treatments which along with the reduction of transpiration in PRD plants, increased instantaneous water use efficiency by 28, 25, and 33% in PRD90-30, PRD70-30, and PRD50-30 treatments, respectively, compared to control. Yield, number of fruits and fruit total soluble solids content were similar among treatments. An increase of 25% in fruit titratable acidity was reached in PRD50-30. Fruit firmness increased up to 31% in PRD treatments. PRD treatments allowed a water irrigation saving up to 46%.     

DNA and morphological diversity of selected Greek tomato (Solanum lycopersicum L.) landraces

Utilizing inter-simple sequence repeats (ISSRs), the genetic diversity of 33 Greek tomato (Solanum lycopersicum L.) landraces and three cultivars, three cherry tomato (S. lycopersicum var.cerasiforme) cultivars and two accessions of Solanum pimpinellifolium L. was studied. Furthermore, 12 ISSR primers were also used to identify 27 morphotypes derived from 7 landraces. Based on Jaccard's coefficient, an average genetic similarity of 0.797 (ranged from 0.56 to 0.95) was found among the accessions. Cluster analysis using the UPGMA method placed all tomato landraces and cultivars into a single group, while the cherry hybrids and the S. pimpinellifolium accessions were placed in a second group. The ISSR data distinguished all the 27 morphotypes from each other and grouped the morphotypes derived from the same landrace together. The ISSR technology proved useful in describing genetic diversity among Greek tomato landraces and was capable of distinguishing the closely related morphotypes.     

Chlorocholine chloride application effects on photosynthetic capacity and photoassimilates partitioning in potato (Solanum tuberosum L.)

Treatment of potato (Solanum tuberosum L.) with chlorocholine chloride (CCC) applied twice as a foliar spray 25 and 30 days after planting has shown to decrease shoot and stolon growth but increase tuber yield. However, the regulatory role of CCC on translocation of recently fixed photoassimilates into different parts of potato plants has not been fully illustrated. In this study, ¹⁴C-isotope labelling technique was used to estimate the photosynthetic capacity and photoassimilate partitioning among leaves, stems, roots + stolons, and tubers of potted potatoes treated with 1.5 g l⁻¹ CCC. CCC treatment significantly increased tuber dry mass but reduced leaf dry mass. CCC-treated leaves had significantly higher chlorophyll and carotenoid contents and assimilated 22.0% more ¹⁴CO₂ per leaf dry mass than the controls. Compared with the control, CCC treatment reduced the translocation of ¹⁴C-photoassimilates into leaves, stems and roots + stolons but increased that into tubers. CCC-treated leaves exported 14.6% more ¹⁴C-photoassimilates into other parts of the plants. In addition, CCC treatment reduced ¹⁴C-soluble sugar and ¹⁴C-starch accumulation in leaves and stems but enhanced them in tubers and roots + stolons. Collectively, the results indicate that CCC treatment significantly improves the photosynthetic capacity of potato leaves and promotes photoassimilates partitioning into tubers thereby enhancing tuber growth.     

Alleviation of salt-induced adverse effects in eggplant (Solanum melongena L.) by glycinebetaine and sugarbeet extracts

Two eggplant cultivars, Dilnasheen and Bemisal, were selected to assess whether pure GB and sugarbeet extract could effectively ameliorate the harmful effects of salt stress on eggplant (Solanum melongena L.), under saline conditions. Salt stress markedly suppressed the growth, yield, photosynthetic capacity, internal CO₂ level, transpiration, and stomatal conductance in both cultivars. Potassium (K⁺) and Ca²⁺ contents and K⁺/Na⁺ ratios of both root and leaf were also reduced, while GB and proline in leaves, and Na⁺ and Cl⁻ contents in roots and leaves were significantly enhanced. Exogenously applied glycinebetaine and sugarbeet extracts significantly counteracted the salt-induced adverse effects on growth, yield, various gas exchange characteristics, GB and leaf K⁺, Ca⁺, Cl⁻ and Na⁺. However, GB and sugarbeet extract showed differential effects on photosynthetic rate, stomatal conductance and transpiration, internal CO₂ level, C_i/C_a ratio, leaf K⁺, Ca²⁺, and Cl⁻ contents, and K⁺/Na⁺ ratio. Sugarbeet extract proved better than the GB in improving growth, photosynthetic rate, transpiration, stomatal conductance, yield and GB accumulation. Since, sugarbeet extract contains a substantial amount of GB along with a variety of other important nutrients so it was found as effective as pure GB in improving growth and some key physiological processes in eggplant under salt stress. Thus, it can be used as an alternative cheaper source of GB for its use as an ameliorative agent for protecting plants against the hazardous effects of salt stress.     

Assessment of genetic diversity and species relationships in eggplant (Solanum melongena L.) using STMS markers

Ninety six accessions including 92 of Solanum melongena and four related non-tuberous species (Solanum insanum, S. incanum, S. integrifolium and S. sysimbriifolium) were taken for the assessment of genetic diversity using 23 STMS primers. Eleven of the 23 primers tested showed polymorphism. The number of alleles per primer ranged from three to six with an average of 4.4. S. melongena had maximum average similarity with its closely related species, S. insanum (0.67) and minimum average similarity with the wild species, S. sysimbriifolium (0.50). The two weedy species S. incanum and S. integrifolium showed more average similarity value of 0.62 and 0.61, respectively with the cultivated S. melongena. S. insanum. S. incanum and S. integrifolium were relatively similar to each other with similarity index value of 0.61 (between S. insanum and S. incanum), 0.63 (between S. insanum and S. integrifolium) and 0.62 (between S. incanum and S. integrifolium). In contrast S. sysimbriifolium was most divergent with the similarity value of 0.49, 0.47 and 0.51 with S. insanum, S. incanum and S. integrifolium, respectively. The closely related species S. insanum and S. incanum, which clustered along with S. melongena accessions, being crossable with cultivated species, constitute important sources of genes that can be introgressed by backcross breeding. Molecular markers can be employed to identify the hybrids and also to monitor introgression of the useful genes.     

The effect of various nitrogen fertilization and foliar nutrition regimes on the concentrations of nitrates,ammonium ions,dry matter and N-total in carrot (Daucus carota L.) roots

Two field experiments (Experiment I in 2003–2005 and Experiment II in 2004–2005) with carrot c.v. ‘Kazan F₁’ were conducted at Trzciana village (50°06′N, 21°85′E). The experiments were arranged in a split-plot design with four replications. Two sub-blocks were identified in both experiments: I, without foliar nutrition; II, receiving plant foliar nutrition. The plants were sprayed three times alternately with: 2% urea solution, 1% solution of multi-component ‘Supervit R’ fertilizer (produced by Intermag, Poland) and again with 2% urea solution. Combinations with diversified nitrogen fertilization were distinguished within both sub-blocks. Experiment I comprised of: (1) Control, (2) Ca(NO₃)₂ 70, (3) Ca(NO₃)₂ 70 + 70, (4) (NH₄)₂SO₄ 70 and (5) (NH₄)₂SO₄ 70 + 70. Experiment II included: (1) Control, (2) ENTEC-26 35 + 35, (3) ENTEC-26 70 + 70, (4) ENTEC 26 105 + 105, (5) NH₄NO₃ 35 + 35, (6) NH₄NO₃ 70 + 70, (7) NH₄NO₃ 105 + 105. Where 70 kg N ha⁻¹ was used before sowing, whereas 35 + 35, 70 + 70 and 105 + 105 kg N ha⁻¹ were applied before sowing and as top dressing. Solid nitrogen fertilizer was added to the soil (produced by): Ca(NO₃)₂, Yara International ASA (Hydro); (NH₄)₂SO₄, Zak?ady Azotowe in Tarnów, Poland; NH₄NO₃, Zak?ady Azotowe in Pu?awy, Poland; and ENTEC-26, COMPO GmbH & Co. KG, Germany. The research aimed at determining the effect of diversified nitrogen fertilization and foliar nutrition on NO₃⁻, NH₄⁺, N-total and dry matter (d.m.) concentrations in carrot, and N uptake by storage roots. In Experiment I, nitrogen fertilization did not affect NO₃⁻ concentration, whereas in Experiment II, the applied N treatment increased NO₃⁻ concentration in carrot in relation to the control, except for the storage roots of plants fertilized with ENTEC-26 35 + 35. Nitrogen fertilization applied in both experiments caused a significant increase in N-total concentration in carrot and N uptake by storage roots in comparison with the control plants. In both experiments, nitrogen fertilization had a different effect on the concentrations of NH₄⁺ and d.m. in carrot. What is more, foliar nutrition treatments in both experiments had a different effect on the concentrations on NO₃⁻, N-total, d.m. in carrot and N uptake by carrot storage roots.     

Effectiveness of water pillow irrigation method on yield and water use efficiency on hot pepper (Capsicum annuum L.)

A study was conducted to elucidate the effect of water pillow (WP) irrigation method, a new alternative method to furrow irrigation, on the yield and water use efficiency (WUE) of hot pepper in a semi-arid climatic condition. In this research, treatments used were: (i) WP method and its 7-day irrigation interval (WP₇), (ii) WP method and its 9-day irrigation interval (WP₉), (iii) WP method and its 11-day irrigation interval (WP₁₁) and (iv) furrow irrigation (FI) method and its 5-day irrigation interval (control) were employed. Although the plants were grown under different irrigation methods and interval conditions, there were no statistical differences in yield and biomass of hot pepper plants between FI and WP treatments (P < 0.05). Water use efficiency (WUE) and irrigation water use efficiency (IWUE) values significantly increased with the application of WP irrigation method (P < 0.05). The highest WUE and IWUE values obtained from WP₁₁ treatment in both years. As a result, we conclude that WP method is a way to save water and increase the yield in semi-arid areas where climatic conditions require repeated irrigation in the hot pepper production area.     

Effect of nitrogen and sulfur interaction on growth and pungency of different pseudostem types of Chinese spring onion (Allium fistulosum L.)

Effects of N and S supply on the growth and pungency (estimated as pyruvic acid levels) of Chinese spring onion (Allium fistulosum L. var. giganteum Makino) were investigated in two pot experiments using soilless growing media. In the first experiment the effects of S supply (0.01 and 4.00 mmol L⁻¹ SO₄²⁻) on the growth and pungency of Chinese spring onion were investigated among four cultivars with fleshy root type or long pseudostem type. In the second experiment the effects of different S (0.01 and 4.00 mmol L⁻¹ SO₄²⁻) and N (1.5, 3.0, 6.0, 12.0 and 24.0 mmol L⁻¹ N) supply levels on the growth and pungency of Chinese spring onion were studied. Fleshy root spring onion had stronger pungency and larger pseudostem diameter than long pseudostem spring onion, and the pungency of fleshy root spring onion was regulated to a greater extent by N and S supply compared with long pseudostem spring onion. Increasing S supply level significantly increased the biomass, N and S uptake and pungency of all cultivars tested. The biomass of Chinese spring onion of fleshy root type (cv Longyao) and long root type (cv Zhangqiu) was more influenced by N supply than it was by cultivar or S supply. Low S supply decreased the pungency of the two cultivars with increasing N supply. No significant differences in N or S uptake or pungency were observed in the two cultivars with different S supply at the N supply level of 1.5 mmol L⁻¹ N, however, cultivar differences in N and S uptake and pungency were investigated at high N supply (12.0 mmol L⁻¹ N) and S supply (4.0 mmol L⁻¹ SO₄²⁻). Excessive N supply (24.0 mmol L⁻¹) significantly inhibited plant growth, retarded S assimilation, and decreased pungency. It is therefore essential to apply the optimum recommended rate of N fertilizer in Chinese spring onion production.