A survey of nitrate NO À 3 and oxalate ((COO À ) 2 ) content in fresh vegetables was conducted in Bari (Italy) over 15 months (from March 1994 to May 1995. A total of 327 samples (edible portions and related sub-samples) were taken from 26 different vegetable types on the wholesale fruit and vegetable market. The data revealed that leaf vegetables (namely rocket, celery, parsley and spinach) contained higher levels of nitrate than bulb, root, shoot, in¯orescence and tuber vegetables. Higher oxalate levels were found in spinach and Swiss chard. Based on consumption data for the whole population provided by the National Institute of Nutrition, daily nitrate intake from vegetables was calculated to be 71 mg. Over 30% of nitrate intake was derived from the consumption of lettuce and Swiss chard.

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With the aim of defining the best management of nutrient solution (NS) in a soilless system for obtaining high quality baby-leaf rocket, the present study focuses on two wild rocket genotypes (“Nature” and “Naturelle”), grown in a greenhouse under two Southern Italy growing conditions—autumn-winter (AW) and winter-spring (WS)—using two soilless cultivation systems (SCS)—at two electrical conductivity values (EC) of NS. The SCSs used were the Floating System (FS) and Ebb and Flow System (EFS) and the EC values were 2.5 and 3.5 dS m−1 (EC2.5; EC3.5) for the AW cycle and 3.5 and 4.5 dS m−1 (EC3.5; EC4.5) for the WS cycle. The yield, bio-physical, physiological and nutritional characteristics were evaluated. Higher fresh (FY) (2.25 vs. 1.50 kg m−2) and dry (DY) (230.6 vs. 106.1 g m−2) weight yield, leaf firmness (dry matter, 104.3 vs. 83.2 g kg−1 FW; specific leaf area, 34.8 vs. 24.2 g cm−2) and antioxidant compounds (vitamin C, 239.0 vs. 152.7 mg kg−1 FW; total phenols, 997 vs. 450 mg GAE mg kg−1 FW; total glucosinulates-GLSs, 1,078.8 vs. 405.7 mg kg−1 DW; total antioxidant capacity-TAC, 11,534 vs. 8,637 μmol eq trolox kg−1 FW) and lower nitrates (1,470 vs. 3,460 mg kg−1 FW) were obtained under WS conditions. The seasonal differences were evident on the GLS profile: some aliphatic GLSs (gluconapoleiferin, glucobrassicanapin) and indolic 4-OH-glucobrassicin were only expressed in WS conditions, while indolic glucobrassicin was only detected in the AW period. Compared with EFS, FS improved leaf firmness, visual quality, antioxidant content (TAC, +11.6%) and reduced nitrate leaf accumulation (−37%). “Naturelle” performed better than “Nature” in terms of yield, visual quality and nutritional profile, with differences more evident under less favorable climatic conditions and when the cultivars were grown in FS. Compared to EC2.5, the EC3.5 treatment did not affect DY while enhancing firmness, visual quality, and antioxidant compounds (TAC, +8%), and reducing the nitrate content (−47%). The EC4.5 treatment reduced FY and DY and the antioxidant content. Despite seasonal climatic condition variability, FS and the moderate salinity level of NS (3.5 dS m−1) can be suggested as optimum.

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The biodiversity in vegetable crops is composed by the genetic diversity, as species diversity (interspecific diversity) and as diversity of genes within a species (intraspecific diversity) referring to the vegetable grown varieties, and by the diversity of agro-ecosystems (agrobiodiversity). Intraspecific diversity is very ample in vegetable crops and is not reflected, at least not to the same extent, in other groups of crops. The labour operated by farmers over centuries of selection has led to the creation of a plurality of local varieties, following domestication of cultivated forms, and wide agro-biodiversity, a precious heritage both from a genetic and a cultural-historical point of view. The Italian National Statistical Institute (ISTAT) takes into account in its annual survey about forty vegetable crops. Intraspecific diversity in vegetables can also be analyzed by examining the information contained in the common catalogue of varieties of vegetable species. The 27 EU Countries as a whole had entered 19,576 varieties of vegetables in the common catalogue as of August 2011. The Netherlands, which represents 8% of total vegetable production in the EU, has registered 7826 varieties. Italy and Spain, which predominate in Europe for the production of vegetables, have registered only 8% (1513) and 9% (1672) of the total varieties, respectively. As a whole 54% of the European varieties entered in the catalogue are hybrids. Puglia, which contributes with about 22% to the Italian vegetable growing area, is among the leading regions for the productions of broccoli raab, celery, parsley, processing tomato, artichoke, endive and escarole, cabbage, fennel, lettuce, cucumber, cauliflower and broccoli, early potato, and asparagus (all with more than 20% of the national area). The region is particularly rich in local vegetable varieties, obtained by farmers themselves after repeated simple selection procedures generation after generation. The local varieties for which there is a strong link with the Puglia traditions and which are described in this review are: carota di Polignano (Polignano carrot) and carota di sant'Ippazio (Saint Ippazio carrot) (Apiaceae), cipolla di Acquaviva delle Fonti (Acquaviva delle Fonti onion) and cipolla bianca di Margherita (Margherita white onion) (Liliaceae), cima di rapa (broccoli raab) (Brassicaceae), unripe melon -carosello, barattiere, meloncella, etc. (Cucurbitaceae), catalogna chicory -cicoria di Molfetta e cicoria di Galatina (Molfetta's chicory and Galatina's chicory) (Asteraceae).

In a growth chamber, endive (Cichorium endivia L. var. crispum Hegi) plants were grown using a solution culture method to evaluate the influence of four ammonium : nitrate (NH4-N : NO3-N) percentage ratios (100:0, 70:30, 30:70, and 0:100) on growth (leaf area, dry mass, crop growth rate, relative growth rate, and net assimilation rate), yield characteristics (head and root fresh mass and root length), quality (dry matter, nitrogen, and nitrate), and inorganic ion content. No symptoms of NH4+ toxicity were detected in endive plants 8 weeks after beginning nutrient treatments. Moreover, by feeding N in mixed form, the growth indices increased compared to indices from feeding with any of the two N forms alone. Ammonium-fed plants produced nitrate-free heads with a fresh mass (171 g) similar to nitrate-fed plants. Compared to the other treatments, the heads of NH4+-fed plants were darker green and more succulent. Mixed N improved yield but caused a remarkable accumulation of nitrate in heads. Following an increase in NO3-N from 30% to 70% in the nutrient solution, head fresh mass rose from 196 to 231 g and NO3- concentration more than doubled (from 2.4 to 6.1 g·kg-1 fresh mass). With 100% of NO3-N, NO3- concentration was 5.5 g·kg-1 fresh mass. With higher NO3-N percentages in the nutrient solution, the difference in the concentration of inorganic cations and anions increased, but K+ concentration was also high in ammonium-fed plants (on average 77 g·kg-1 dry mass). Head total N accumulation was increased by the presence of NH4+ in the nutrient solution and decreased with 100% NO3-N. From the commercial viewpoint, the produce obtained from 100% NH4-N was good, with the value-added factor of the absence of nitrate. This may be an extremely remarkable factor because of the commercial limits on the allowable nitrate content in leafy vegetables already enforced by many European countries and those the European Union is going to adopt in a directive.