Research to improve human health expected to benefit growers
Broccoli originated in the Italian province of Calabria, and Americans started growing Calabrese broccoli about 200 years ago. Today there are many varieties, but not all broccoli varieties are created equal. Amounts of anticarcinogenic compounds vary by type.
In 1996, a Ph.D. student in molecular genetics at the University of Illinois began exploring broccoli. Today, Dr. Allan Brown leads research at the Plants for Human Health Institute, a private/public venture connected with the Department of Horticultural Science at North Carolina State University in Kannapolis.
According to Brown, levels of luteins, alpha-tocopherol (vitamin E) and glucosinolates are higher in broccoli than in other cruciferous vegetables. Broccoli also contains sulforaphane, a glucosinolate that is not found in other cruciferous veggies. Sulforaphane prevents the induction and progression of tumors. Brown’s research has shown a tenfold difference between the highest and lowest levels of these glucosinolates among commercial broccoli material.
Environment and growing conditions do affect the plant’s ability to produce these health-promoting compounds. Still, Brown says there appear to be differences in the genetic composition of the broccoli lines that produce higher levels of glucosinolates, especially sulforaphane.
Using classical breeding techniques, Brown and his team are crossing Broccoletti Neri e Cespuglio, a landrace strain of broccoli from the Roman countryside, with cultivated broccoli material commonly grown in the U.S. The intention is to produce broccoli with higher levels of sulforaphane and other health-promoting compounds.
“At this point, we are seeing material that has much higher levels than what we’re seeing on the market. We are still doing a number of crosses back to this material in order to bring back all the horticultural characteristics that you associate with broccoli,” he reports.
Brown explains that the wild material contains undesirable characteristics, such as a single small head. “It’s an attractive-looking plant, but to be competitive on the horticultural traits, we need to make a couple more backcrosses to try to restore some of the horticultural characteristics.”
Thanks to the molecular markers associated with the genes that produce these compounds, the researchers are not at risk of losing any of the characteristics they so carefully bred for in the first place. Brown and his team follow these molecular markers as they go from one generation to the next.
Currently at the sixth generation, Brown’s high-sulforaphane broccoli is almost ready to be released as inbred. However, the researcher intends to spend a couple more years refining the cultivar before releasing it to the public.
Although competition is already on the market, Brown is not concerned. Earlier this year, Apio and partner Monsanto released patented Beneforté broccoli (a trademark of Seminis Vegetable Seeds), with high levels of the phytonutrient glucoraphinin, which breaks down into sulforaphane when eaten and naturally boosts the body’s enzyme levels. Apio claims Beneforté has two to three times as much glucoraphinin as broccoli varieties commonly found in the U.S. This is the first broccoli to be released as a high glucosinolate level broccoli. Brown believes his broccoli will have higher levels of the phytonutrient than Beneforté, but he hasn’t yet grown them side by side to prove his theory.
With the initial cross, Brown and his team created a population of 165 plants. Among the 165 plants, differences exist in the phytonutrients and compounds mentioned above. Differences also exist in several other traits, including maturity, head size, leaf shape and the amount of wax on the leaves. Each of these characteristic variations may have a commercial impact. For example, waxiness may be involved in drought tolerance. Brown hasn’t yet reached the point where he can associate the phytonutrients involved in flavor attributes, but he anticipates that researchers will soon be able to connect phytonutrient compounds with flavor attributes.
With time, Brown could create a super strain of broccoli. However, at the moment, he’s concentrating on increasing the health benefits. “We are selecting among these 165 families [and] using the 165 families in studies to determine the effects of individual compounds in broccoli on heart disease, cancer and other chronic diseases. Each family of broccoli has a different combination of genes that impact these diseases. We can look at the relative importance of glucosinolates, lutein, tocopherols, beta-carotene, etc., and we can look at interactions between these compounds. Do two or more do a better job at inhibiting cancer than only one?” he asks. Brown hopes to combine all of these health-promoting compounds into one broccoli material.
What will this more nutritious variety of broccoli cost growers to produce? Brown sees no difference in the cost of production between current varieties on the market and the one he is developing. “It will be more of a value-added feature,” he asserts.
Once it’s released in 2013 or 2014, Brown may move on to create value-added cultivars of other brassicas by making crosses between broccoli and other cruciferous vegetables. If he has his way, the brassicas of the future will all have higher levels of sulforaphane.
The author is a freelance writer based in Massachusetts and a monthly contributor to Growing.