The study of the diversity within and between major Solanaceae crops (pepper, tomato, eggplant) is of interest for the selection and development of balanced diets. We have measured thirty-six major fruit composition traits, encompassing sugars, organic acids, antioxidants and minerals, in a set of 10 accessions per crop for pepper, tomato and eggplant, grown under the same cultivation conditions. The aim was to evaluate the diversity within species and to provide an accurate comparison of fruit composition among species by reducing to a minimum the environmental effect. Pepper, tomato and eggplant had a clearly distinct composition profile. Pepper showed the highest average content in total sugars and organic acids. Fructose and glucose were the major sugar compounds in the three species, although in pepper and tomato sucrose was present only in trace amounts. Citric acid was the major organic acid in pepper and tomato, while in eggplant it was malic acid. Pepper and eggplant had the highest total antioxidant activity. Vitamin C content was much higher in pepper than in tomato and eggplant, while eggplant accumulated high concentrations of chlorogenic acid. Furthermore, eggplant was the species with higher content in most minerals, particularly for K, Mg and Cu, while pepper was the richest in Fe. Due to their complementary nutritional profiles, a combined regular consumption of the three vegetables would supply more than 20% of the Dietary Reference Intake of several of the analysed phytochemicals. The large diversity within each species is of interest for selecting varieties with better nutritional and organoleptic profiles, as well as for breeding new cultivars.

The ‘de penjar’ tomato (Solanum lycopersicum L.) is a group of local varieties from the Spanish Mediterranean region carrying the alc mutation, which provides long shelf-life. Their evolution under low-input management practices has led to the selection of resilient genotypes to adverse conditions. Here we present the first evaluation on nutritional fruit composition of a collection of 44 varieties of ‘de penjar’ tomato under two N fertilization levels, provided by doses of manure equivalent to 162 kg N ha^–1 in the high N treatment and 49 kg N ha^–1 in the low N treatment. Twenty-seven fruit composition and quality traits, as well as plant yield and SPAD value, were evaluated. A large variation was observed, with lycopene being the composition trait with the highest relative range of variation (over 4-fold) under both N treatments, and significant differences among varieties were detected for all traits. While yield and most quality traits were not affected by the reduction in N fertilization, fruits from the low N treatment had, on average, higher values for hue (5.9%) and lower for fructose (−11.5%), glucose (−15.8%), and total sweetness index (−12.9%). In addition, lycopene and β-carotene presented a strongly significant genotype × N input interaction. Local varieties had higher values than commercial varieties for traits related to the ratio of sweetness to acidity and for vitamin C, which reinforces the appreciation for their organoleptic and nutritional quality. Highest-yielding varieties under both conditions displayed wide variation in the composition and quality profiles, which may allow the selection of specific ideotypes with high quality under low N conditions. These results revealed the potential of ‘de penjar’ varieties as a genetic resource in breeding for low N inputs and improving the organoleptic and nutritional tomato fruit quality.

Selection and breeding of eggplant (Solanum melongena) materials with good performance under low nitrogen (N) fertilization inputs is a major breeding objective to reduce environmental degradation, risks for human health, and production costs. Solanum elaeagnifolium, an eggplant wild relative, is a potential source of variation for introgression breeding in eggplant. We evaluated 24 plant, fruit, and composition traits in a set of genotyped advanced backcrosses (BC2 and BC3) of eggplant with S. elaeagnifolium introgressions under low N conditions. Significant differences were found between the two parents for most traits, and a wide phenotypic diversity was observed in the advanced backcrosses, with some individuals with a much higher yield, nitrogen use efficiency (NUE), and phenolics content than the S. melongena parent. In general, the lower the proportion of S. elaeagnifolium genome introgressed in the advanced backcrosses, the higher was the general phenotypic resemblance to S. melongena. Putative QTLs were detected for stem diameter (pd4), presence of prickles in stem (ps6), leaf (pl6) and fruit calyx (pc6), fruit width (fw7), chlorogenic acid content (cg5), total phenolic acid peaks area (ph6), chlorogenic acid peak area (ca1), and phenolic acids pattern (cp1). Our results reveal that introgression breeding of eggplant with S. elaeagnifolium has a great interest for eggplant breeding, particularly for adaptation to low N conditions. These materials can potentially contribute to the development of improved eggplant varieties for a more sustainable agriculture.

The wild species Solanum incanum has been used as a donor parent for the development of a set of eggplant introgression lines (ILs), which are of interest for breeding for stress tolerances and relevant morpho-agronomic traits but could also be useful for breeding for fruit quality, due to the generally higher content in health-promoting compounds of S. incanum. The use of eggplant ILs with introgressions from S. incanum requires ensuring that glycoalkaloids levels are below safety limits. We evaluated 25 fruit composition traits, including proximate composition, sugars, acids, phenolics, glycoalkaloids, and minerals in a set of 16 eggplant ILs with S. incanum, both parents and the F₁, grown under two environments (open field and screenhouse). The results demonstrated that the parents were significantly different regarding most fruit composition traits. Large variation was found among the 16 ILs for all traits analyzed and a strong influence of the environment accounted for the variation of 17 out of the 25 traits evaluated. Although the S. incanum parent produced fruits with high levels of glycoalkaloids, the 16 ILs showed mean values of total glycoalkaloids below the currently accepted safety limit for human consumption (200 mg kg⁻¹ fresh weight). Overall, the ILs produced fruits that are safe for consumption, with nutritional and functional quality similar to the recipient parent. Furthermore, six putative QTLs were detected spread over chromosomes 3 for crude protein, 5 for malic and total acids, and 7 for chlorogenic acid and solamargine, and potential candidate genes were spotted for most of them, which provide new relevant information for eggplant breeding.