María D. Raigón

Effects of Organic and Conventional Cultivation Methods on Composition of Eggplant Fruits

Organic food is associated by the general public with improved nutritional properties, and this has led to increasing demand for organic vegetables. The effects of organic and conventional cultivation methods on dry matter, protein, minerals, and total phenolic content has been studied for two successive years in two landraces and one commercial hybrid of eggplant. In the first year, organically produced eggplants had higher mean contents (expressed on a fresh weight basis) of K (196 vs 171 mg 100 g(-1)), Ca (11.1 vs 8.7 mg 100 g(-1)), Mg (6.0 vs 4.6 mg 100 g(-1)), and total phenolics (49.8 vs 38.2 mg 100 g(-1)) than conventionally grown eggplants. In the second year, in which matched plots having a history of organic management were cultivated following organic or conventional fertilization practices, organically produced eggplants still had higher contents of K (272 vs 249 mg 100 g(-1)) and Mg (8.8 vs 7.6), as well as of Cu (0.079 vs 0.065 mg 100 g(-1)), than conventionally fertilized eggplants. Conventionally cultivated eggplants had a higher polyphenol oxidase activity than organically cultivated ones (3.19 vs 2.17 enzyme activity units), although no differences in browning were observed. Important differences in mineral concentrations between years were detected, which resulted in many correlations among mineral contents being significant. The first component of the principal component analysis separates the eggplants according to year, whereas the second component separates them according to the cultivation method (organic or conventional). Overall, the results show that organic management and fertilization have a positive effect on the accumulation of certain beneficial minerals and phenolic compounds in eggplant and that organically and conventionally produced eggplants might be distinguished according to their composition profiles.

Diversity for chemical composition in a collection of different varietal types of tree tomato (Solanum betaceum Cav.), an Andean exotic fruit

We evaluated 23 tree tomato (Solanum betaceum) accessions from five cultivar groups and one wild relative (Solanum cajanumense) for 26 composition traits. For all traits we found highly significant differences (P<0.001) among the materials studied. The high diversity found within S. betaceum for composition traits was matched by a high diversity within each of the cultivar groups. We found that sucrose and citric acid were the most important soluble sugar and organic acid, respectively, in tree tomato. Fruit in the anthocyanin pigmented (purple) group had a carotenoid content similar to that in the yellow-orange cultivar groups. Total phenolic content was significantly correlated (r=0.8607) with antioxidant activity. Analyses of mineral content showed that tree tomato is a good source of K, Mg, and Cu. Multivariate principal components analysis (PCA) confirmed that an important diversity exists within each cultivar group. The results we have obtained indicate that the high diversity found within the tree tomato could be exploited for selection and breeding for developing the tree tomato as a commercial crop.

Characterization of composition traits related to organoleptic and functional quality for the differentiation, selection and enhancement of local varieties of tomato from different cultivar groups.

Tomato (Solanum lycopersicum) local varieties are having an increasing demand. We characterized 69 local tomato accessions from eight cultivar groups for proximate composition traits, major sugars, acids and antioxidants. A large diversity was found, with differences among accessions of almost tenfold for lycopene. Significant differences were found among cultivar group means for most traits. The Cherry and Penjar groups generally presented higher dry matter, soluble solids content, titratable acidity, taste index, β-carotene, ascorbic acid, total phenolics, and antioxidant activity that the other groups. Wide ranges of variation were found within each cultivar group. Positive correlations were found between proximate traits related to taste and antioxidants. The multivariate principal components analysis confirms the distinct profile of the Cherry and Penjar groups and the large variation within groups. The results will be useful for the differentiation, enhancement and selection of local tomato varieties with improved organoleptic properties and functional quality.

Characterization of interspecific hybrids and first backcross generations from crosses between two cultivated eggplants (Solanum melongena and S. aethiopicum Kumba group) and implications for eggplant breeding

Common (Solanum melongena L.) and scarlet (S. aethiopicum L.) eggplants are cultivated for their fruits and form part of the same genepool. We have studied plant and fruit characteristics, pollen viability and seed set, phenolics content, and fruit flesh browning in accessions of S. melongena and S. aethiopicum Kumba group, as well as interspecific hybrids between these species and first backcross generations to each parental species. Respective genotypes were also characterized with seven polymorphic SSR markers. The results demonstrate that many differences exist for plant and fruit morphology among S. melongena, S. aethiopicum and the interspecific hybrids. The latter are very vigorous and generally intermediate between the two parents, except for fruit size which is smaller (and parthenocarpic due to a high pollen sterility) than those of any of the parents. Backcross progenies also exhibited morphological variation with moderate heritability values for the attributes evaluated. Variation for fruit size was present in the backcross generations but fruits were small resulting in little variation for fruit shape. Backcross plants with moderate fertility produced seeded fruits. Primary hybrids had fruit phenolics content similar to that of S. aethiopicum, the parent with lowest phenolics concentration, and were heterotic for fruit flesh browning. Backcross progenies were quite variable for both traits. SSR markers did not reveal segregation distortion in the backcross generations for these interspecific hybrids. The results demonstrate that generations derived from sexual interspecific hybridization can be a powerful tool for S. melongena and S. aethiopicum Kumba group breeding.

The role of traditional varieties of tomato as sources of functional compounds

BACKGROUND Traditional varieties of tomato, usually associated with excellent organoleptic quality, are increasingly appreciated in European quality markets. A collection of 126 populations of 16 traditional varieties from the east of Spain (a secondary diversity center for tomato) have been evaluated over 2 years in order to determine their potential value as sources of functional compounds, including ascorbic acid, lycopene, β-carotene and total phenolic content. RESULTS Population and population × year interaction significantly affected lycopene and ascorbic acid contents, while year effect was also significant for β-carotene. Despite finding some global trends in certain varieties concerning their functional value, high levels of variation have been found at the intra-varietal level. Populations with high levels of the compounds analysed have been found, as well as different levels of intra-population and inter-year variation. Maximum mean contents for both years have reached 308 mg kg(-1) ascorbic acid, 130 mg kg(-1) lycopene, 30 mg kg(-1) β-carotene and 89 mg caffeic acid 100 g(-1) total phenolic contents, though it is difficult to identify accessions with joint high values of the three compounds. CONCLUSION These results open the possibility to promote traditional materials as sources of functional compounds, thus strengthening their quality niches and consolidating their price premium. Additionally, these materials could also be used in breeding programs for quality.

The use of slow-release fertilizers in citrus

SummaryIn the last decades, an important change has taken place in agricultural practices to increase production and thus the economic yield of citrus. This increase has been supported mainly by new irrigable areas and the wider use of fertilizers, especially nitrogenous ones. The efficiency of nitrogenous fertilization is highly variable. A great part of the nitrogen applied to the soil is lost by leaching, causing problems in the environment due to water pollution by nitrates. Slow-release fertilizers can be alternatives to increase efficiency and can reduce the polluting action of the fertilizers, especially in intensive agricultural areas. In this work, all publications found up to date dealing with the utilization of slow-release fertilizers in citrus seedlings and in young and mature trees are reviewed. Attention is paid to the studied responses (growth of the tree, content of nutrients in leaves and soils and the production and quality of the crop), as a function of the type of fertilizer employed ...

Phenolics content, fruit flesh colour and browning in cultivated eggplant, wild relatives and interspecific hybrids and implications for fruit quality breeding

Increasing the content in bioactive phenolics in the eggplant (Solanum melongena) fruit is of interest, but may result in enhanced browning. We evaluated six varieties of S. melongena, 22 accessions of wild related species and 42 interspecific hybrids between cultivated eggplant and wild relatives for phenolics content, fruit flesh colour, polyphenol oxidase (PPO) activity, and fruit flesh browning. Wild relatives generally had a higher content in phenolics and a broader range of variation than cultivated eggplant. Chlorogenic acid was the predominant (>65.0%) phenolic acid in cultivated eggplant and its primary genepool wild ancestor S. insanum, while for the other wild species on average represented <50% of the chromatogram peak area. Fruit flesh colour was lighter in S. melongena than in the wild species, while PPO activity and browning was much higher in wild species of the secondary and tertiary genepools. Interspecific hybrids between S. melongena and S. insanum were intermediate in their characteristics, while those with secondary and tertiary genepool species were more similar to the wild species. No significant correlations were found between total phenolics or chlorogenic acid contents and fruit flesh browning, but PPO activity was correlated to both the degree of browning (r=0.404) and colour difference (r=0.458). The results indicate that wild species can contribute to improving the bioactive properties of eggplant without affecting negatively fruit flesh colour and browning.

Fruit composition diversity in land races and modern pepino (Solanum muricatum) varieties and wild related species

Pepino (Solanum muricatum) fruits from 15 accessions of cultivated pepino as well as six accessions from wild relatives were evaluated for contents in dry matter, protein, β-carotene, chlorophylls and seven minerals. Several-fold differences among accessions were found for most traits. Average values obtained were similar to those of melon and cucumber, but the phenolic contents were much higher. Wild species had significantly higher average contents for all traits vs. the cultivated pepino accessions. And, the comparisons among the cultivated pepino varieties showed that the modern varieties were more uniform in composition, and they possessed significantly lower concentrations of protein, P, K, and Zn than local land races. Most of the significant correlations among composition traits were positive. Our studies show that regular consumption of pepino fruits could make a significant contribution to the recommended daily intake of P, K, Fe and Cu as well as to the average daily intake of phenolics. Furthermore, the higher values for most nutrients measured in the wild species and in the local land races indicate that new pepino varieties with improved fruit contents in nutrient and bioactive compounds can be developed.

Available N in the root area for citrus orchards fertilized with sulphur-coated-urea and ammonium nitro-sulphate

The leaching of N fertilizers in citrus causes important N losses, thus exerting a direct influence on the economy of citrus production, and may have negative consequences on the environment. The use of controlled-release N fertilizers may reduce leaching and be a solution to this problem.The amounts of available N, expressed as g of N in a soil cylinder corresponding to the drip area of the tree and of 0–60 cm depth, were compared at different vegetative periods, in an orange orchard, for four treatments; two doses of a standard fertilizer (ammonium nitrate sulphate, ANS), applied in the quantities of 11.55 kg N/ha (ANS-350) and 49.50 kg N/ha (ANS-2×750) and two doses of a slow-release fertilizer (sulphur-coated urea, SCU), applied in the quantities of 11.55 kg N/ha (SCU-350) and 24.25 kg N/ha (SCU-750), in nine consecutive years. A treatment without N (no N) was included. Available total N throughout the whole of the vegetative cycle, and in partial critical periods, has been determined as another comparison term. In the same way, non-available N has been measured at the beginning and at the end of the experiment.SCU treatment applied in low doses and only in spring maintained high levels of available N in soil during the vegetative cycle, reducing N losses, compared with ANS treatments. In the whole annual cycle, the amounts of N with SCU-750 were 32% greater than those of ANS-(2×750) though the quantity of N applied with this treatment was double. SCU-350 provided 5% less N than ANS-(2×750), though the dose of N applied with this treatment was 4.3 times greater. In all critical periods, SCU-750 maintained quantities of N higher than those with ANS-(2×750). For SCU-350, the amounts of N were similar to those of ANS-(2×750), except in summer as a consequence of the second fertilization with ANS-(2×750). Non-available N increased during the experiment in all treatments providing N except in ANS-350. A good crop and quality of fruits were obtained with SCU treatments, which in conjuntion with the reduction in dosage and rates justified its application.

A simplified method for the extraction and analysis of available nitrogen, phosphorus, and potassium in soils

Abstract Sodium bicarbonate (NaHCO3) and calcium chloride (CaCl2) are proposed as simultaneous extractants of available nitrate‐nitrogen (NO3 ‐‐N), phosphorus (P), potassium (K) in soils. Flow Injection methods were used for the determination of NO3 ‐ and P, and atomic emission spectroscopy for K. Parameters, such as reproducibility, precision, and recovery of the different extraction processes were studied. The usefulness of the proposed extractants was tested by applying them to different samples from the Spanish Soil Collection. The results obtained were compared with those provided after using the extractants recommended by the official methods. Sodium bicarbonate turned out to be suitable for the simultaneous extraction of NO3 ‐, P, and K in alkaline soils, whereas CaCl2 was only advisable for NO3 ‐.