NOVELTY - A crop having ability to accumulate selenium (Se) or Se-methylselenocysteine in its edible portion is cultivated in a growth environment containing selenite for accumulating Se or Se-methylselenocysteine in the edible portions, and harvesting the edible portion of the plant which comprises accumulated Se.    USE - For producing edible plants, useful as nutritional supplement and also in production of chemopreventive agents (all claimed). The supplement reduces risks due to cancer and cardiovascular diseases, improves immunity and increases resistance to viral infections, in both humans and animals.    ADVANTAGE - The production of edible plants with a significant concentration of selenium (Se) or Se-methylselenocysteine effectively increases availability of selenite in plants. The method enables uniform and reproducible accumulation of controllable amount of metals in edible plants. It effectively increases their bio-availability, and utilizes a hydroponic growth environment which is easily controlled. The method does not involve addition of undesirable contaminants into the edible plant. The uptake of Se in plant tissue effectively enhances gene expression, thereby increasing production of non-toxic Se metabolites within the plant. The edible portion of the plant containing nutritionally valuable metals can be directly consumed or effectively formulated into capsules, tablets, powders, gels or liquids. The method minimizes or eliminates safety hazards.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (i) An isolated edible plant which has been genetically engineered to accumulate more Se in its edible portions.    (ii) A nutritional supplement comprising the edible portions of the plant hyperaccumulated with Se. The supplement is incorporated in processed food, capsule, tablet, powder, gel and/or liquid.    (iii) Production of chemopreventive agents, which involves harvesting at least some edible portions of the plant with accumulated Se, and incorporating the harvested portions into nutritional supplements in the form of processed food, chemotherapeutic agent, capsule, tablet, powder, gel or liquid.    (iv) Production of genetically engineered plant capable of accumulating Se, which involves identifying the enzymes in the plant capable of accumulating Se, cloning the genes encoding the enzymes capable of accumulating Se, and transforming the genes encoding the enzymes into an edible plant.    (v) Preparation of a nutritional supplement which involves incorporating the plant containing Se-methylselenocysteine or Se in its edible portions into a nutritional supplement.