Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2003
Publication Date: 1/10/2004
Citation: Farnham, M.W., Stephenson, K.K., Fahey, J.W. 2004. Glucoraphanin level in broccoli seed is largely determined by genotype. HortScience. 40:50-53.
Interpretive Summary: Broccoli has received increasing attention in recent years because it contains relatively high levels of the compounds glucoraphanin and sulforaphane that when consumed may provide protection against certain cancers in humans. The discovery that broccoli sprouts have 10 to 100 times more glucoraphanin than the mature vegetable head has stimulated commercial interest in broccoli seed and sprouts as new food products. As a consequence, seed suppliers have experienced unprecedented demand for broccoli seed. We previously evaluated and identified varieties of broccoli developed by the ARS cole crop breeding program that can serve as better sources of relatively cheap and uniform broccoli seed to replace existing lower quality sources presently available to sprouters. In this current study, we present results showing that several of the previously characterized, high-yielding broccoli varieties have added value in that they produce seed with high glucoraphanin concentration. These varieties have strong commercial potential for producing seed that can be used to produce seedling sprouts that may ultimately offer a health promoting effect when eaten by consumers. Commercial seed companies and the sprout industry that they supply seed to are very interested in this work and the broccoli varieties resulting from it, and they are engaged with us in cooperative efforts to move this technology into the marketplace.
Technical Abstract: Broccoli (Brassica oleracea L., Italica Group) seedling sprouts are known to contain approximately ten-fold higher levels of glucoraphanin than broccoli heads. This finding is significant in light of the fact that glucoraphanin is hydrolyzed to sulforaphane, a constituent that may provide chemoprotection against certain carcinogens. High levels of glucoraphanin in sprouts occur as a result of high levels in mature broccoli seed, and this has stimulated interest in broccoli seed production. In the current study, our objective was to evaluate the relative importance of genotype versus environment as a determinant of glucoraphanin and glucoiberin concentration in broccoli seed. Previously described broccoli seed lots harvested off eleven broccoli inbreds grown in two greenhouse and two screen cage environments were assayed for glucoraphanin and glucoiberin content. Seed glucoraphanin level ranged from 5 to 100 umole/g seed, and glucoiberin ranged from 0 to about 40 umole/g seed, regardless of production environment. Analysis of variance indicated that genotype was the most significant factor influencing levels of the two glucosinolates.Although significant environmental and genotype-by-environment effects were observed for glucoraphanin level and a significant genotype-by-environment effect was observed for glucoiberin, these effects were small compared to those for genotype. Results indicate that it is possible to identify broccoli inbreds that consistently produce relatively high yields of high glucoraphanin seed across different environments.