ZAHRADNÍKOVÁ HELENA, PETŘÍKOVÁ KRISTÍNA: Nematocid eff ects of watercress (Nasturtium offi cinale R. Br.). Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 1, pp. 233-236 The watercress (Nasturtium offi cinale R. Br.) is o en grown as a forced leaf vegetable rich in vitamins and minerals. Its specifi c taste and curative eff ects result from the presence of mustard glycosides (glucosinolates) that may also show nematocidic eff ects. The aim of this study was to evaluate the eff ect of watercress eluate and juice on tomato plants inoculated with the northern root-knot nematode (NRKN) Meloidogyne hapla. It was found out that a er the treatment of plants with solutions derived from watercress the yield of fruit was highly signifi cantly increased. The highest yield increase (by 96 % to 165 %) was observed in the variant with the highest concentration of watercress extracts (macerate + 200 ml of juice). Although at lower concentrations of watercress solution the increase in yields was also reduced (by 57-118 %), the diff erence was still statistically highly signifi cant. The eff ect of this treatment on the content of vitamin C was similar and the increase was also highly signifi cant and ranged from 24 to 67 %. When evaluating the occurrence of nematodes on roots of tomato plants, the presence of pathogens was equal to zero percent in all treated variants. The treatment with this phytosolution corroborated not only a nematocidic eff ect of watercress but also its positive infl uence on the yield and level of vitamin C in dependence on increasing concentrations of the eff ective agent. It can be therefore concluded that the watercress solution showed a promoting eff ect on tomato plants.watercress, nematocidic eff ects, tomato, yield, vitamin C The watercress Nasturtium offi cinale R. Br. is a member of Brassicaceae family and is cultivated as a perennial, nutritionally valuable and tasty forced vegetable that is popular in a number of countries. It is rich in chemoprotective substances.