Se-enrichment of cucumber (Cucumis sativus L.), lettuce (Lactuca sativa L.) and tomato (Solanum lycopersicum L. Karst) through fortification in pre-transplanting

We propose a new method for the fortification of crop plants with Se, based on the use of Se-enriched peat during the pre-transplanting stage. The method is as follows: (i) enrich in Se an appropriate amount of peat; (ii) sow the seeds of the selected crop species in Se-enriched peat until seedlings have the appropriate size for transplanting; (iii) transfer these Se-enriched transplants in the field. Concentrations ranging from 10 to 20 mg Se per kilogram of dry peat induced a Se-enrichment in transplants without negative effects on plant growth, while higher concentrations induced a severe reduction of plant growth. Those fortified transplants showed Se concentrations from 2 to 78 times higher than those observed in the untreated control. After transplanting in the field, the edible organs of Se-enriched plants at the end of cropping cycle showed Se concentrations from 1.6 (tomato) to 8.5 (lettuce) times higher with respect to the untreated controls. The final Se concentrations in Se-enriched edible organs (on a fresh weight basis) were 29.3-48.0 μg kg−1 for cucumber fruits, 22.7-53.4 μg kg−1 for lettuce leaves and 15.2-19.9 μg kg−1 for tomato fruits, depending on the experimental year. Plants fortified with the above technique did not show any negative effects in terms of yield level and quality with respect to controls. On the contrary, a slightly higher shelf-life (lettuce) and an increased level of vitamin A (tomato) were noted in some instances, with respect to non-enriched controls.