Mineral Concentration of Broccoli Florets in Relation to Year of Cultivar Release

It has been proposed that crop improvement through directed plant breeding has resulted in decreases in nutrient concentrations of harvested components over time. A few field studies wherein cultivars released over a period of years are evaluated for nutrient content provide the best evidence for nutrient changes over time; however, no such studies have been conducted with vegetable crops. To accomplish this with broccoli (Brassica oleracea L.), we grew 14 cultivars released over 50 yr in two field trials, and harvested florets were assayed for mineral concentration by inductively coupled plasma–optical emission spectroscopy. Results indicated significant cultivar differences in floret concentrations of Ca, Cu, Fe, Mg, Na, P, and Zn, but not of K, Mn, Mo, or S. With most minerals, there was no clear relationship between concentration and release year. Although the oldest cultivar exhibited some of the higher mineral concentrations, from 1975 to the present no significant changes appear to have occurred. Head mass was negatively correlated with concentrations of most minerals, but head mass was not correlated with year of release. We propose it most relevant to examine mineral nutrient changes for cultivars grown since 1975 when broccoli phenotypes changed dramatically and the vegetable grew in prominence as a component in the U.S. diet. Results provide a guide for mineral levels in broccoli that should be maintained as other characteristics are manipulated in the future.