It is widely accepted that a healthy diet is an important factor in preventing chronic diseases, and in improving energy balance and weight management. Studies have shown strong inverse correlations between tomato consumption and the risk of certain types of cancer, cardiovascular diseases and age-related macular degeneration. Because tomato is the second-most important vegetable in the world after potato, this horticultural crop constitutes an excellent source of health-promoting compounds due to the balanced mixture of minerals and antioxidants including vitamins C and E, lycopene, b-carotene, lutein and flavonoids such as quercetin. Improvement in phytonutrients in tomatoes can be achieved by cultivar selection, environmental factors, agronomic practices, stage of ripeness at harvest, and appropriate handling and conditioning all the way from the field to the consumer. The purpose of this paper is to review the recent literature of the main factors that can improve the nutritional quality of tomato and consequently their beneficial role in human diet. The importance of genotype selection and the optimization of environmental conditions (light, temperature, humidity, atmospheric CO 2 and air pollutants) for high nutritional value is outlined first, followed by the optimization of agricultural practices (soil properties, water quality, mineral nutrition, salinity, grafting, pruning, growing systems, growth promoters, maturity, and mechanical and pest injuries). The review concludes by identifying several prospects for future research such as modelling and genetic engineering of the nutritional value of tomato.

Recirculating nutrient systems offer a good method to control nutrient leaching from greenhouses into the environment. However, the potential for the rapid spread of root diseases is the main hindrance to adoption of recirculating nutrient systems by the greenhouse industry. This review discusses and compares five broadly different methods of disease control in these systems, namely heat, filtration, chemical, radiation and biological control. Each has strengths and weaknesses, but all have been found to be effective in terms of pathogen control. Sterilization (heat, oxidizing chemicals, UV radiation) and membrane filtration methods are generally very effective, but may adversely affect beneficial microorganisms in the recirculated solution. Slow filtration and microbial inoculation methods are less disruptive of the microflora, but effectiveness may vary with the pathogen. Microbial inoculation holds the promise of very targeted disease suppression, but few products are commercially available. recirculation / disinfestation / hydroponics / disinfection / root diseaseRésumé -Désinfestation des solutions nutritives recyclées en horticulture sous serre. L'utilisation de systèmes de recirculation des nutriments est une bonne façon de contrôler le lessivage des nutriments des serres dans l'environnement. Toutefois, le risque de propagation rapide de maladies des racines est le principal obstacle à l'adoption de tels systèmes par l'industrie serricole. La présente étude examine et compare cinq façons distinctes de contrer les maladies dans ces systèmes, à savoir le traitement thermique, la filtration, le traitement chimique, le rayonnement et la lutte biologique. Chacune de ces méthodes a ses points forts et ses points faibles, mais toutes se sont révélées efficaces pour combattre les pathogènes. La stérilisation (par la chaleur, l'utilisation d'agents oxydants ou le rayonnement ultraviolet) et la filtration sur membrane sont habituellement très efficaces, mais peuvent nuire aux microorganismes utiles dans la solution recirculée. La filtration lente et l'inoculation microbienne sont moins nuisibles à la microflore, mais leur efficacité peut varier selon le pathogène. L'inoculation microbienne permet une élimination très sélective des maladies, mais peu d'inoculants microbiens sont disponibles dans le commerce. recirculation / désinfestation / culture hydroponique / désinfection / maladie des racinesAgronomie 21 (2001) 323-339 323

No abstract

Arbuscular mycorrhizal (AM) fungi can affect many different micronutrients and macronutrients in plants and also influence host volatile compound synthesis. Their effect on the edible portions of plants is less clear. Two separate studies were performed to investigate whether inoculation by AM fungi (Rhizophagus irregularis, Funneliformis mosseae, or both) can affect the food quality of tomato fruits, in particular common minerals, antioxidants, carotenoids, a suite of vitamins, and flavor compounds (sugars, titratable acids, volatile compounds). It was found that AM fungal inoculation increased the nutrient quality of tomato fruits for most nutrients except vitamins. Fruit mineral concentration increased with inoculation (particularly N, P, and Cu). Similarly, inoculated plants had fruit with higher antioxidant capacity and more carotenoids. Furthermore, five volatile compounds were significantly higher in AM plants compared with non-AM controls. Taken together, these results show that AM fungi represent a promising resource for improving both sustainable food production and human nutritional needs.

Abstract. The mobility and deposition of silicon (Si) in cucumber plants grown in hydroponic culture were studied using scanning electron microscopy and energy dispersive X‐ray analysis under conditions of powdery mildew fungus infection. Following transfer to Si containing media, plants grown in the absence of Si showed rapid silicification of leafy tissue, primarily in the trichome bases. These plants also exhibited increased disease resistance to Sphaerotheca fuliginea (Schlecht.:Fr.) Poll, and concentration of Si in the leaf epidermis surrounding the invading pathogen. Plants grown in Si‐supplemented media and transferred into Si‐deficient media contained residual Si in the leaf trichome bases, but failed to display disease resistance or silicification of host tissue surrounding the invading pathogen.