Research on asparagus, much of which has been done at Rutgers, has uncovered the following components with potential health effects: flavonoids, saponins, oligosaccharides, carotenoids and amino acids. Two phytochemicals that Rutgers researchers are looking at are protodioscin and rutin. Much research still remains before scientists have conclusive evidence, but these compounds show promise in inhibiting a number of cancers cells (most notable colon cancer and leukemia), lowering cholesterol and providing numerous other health benefits. Protodioscin is an aphrodisiac present in asparagus that has been linked to improvement of sexual performance.
Asparagus is also one of the most nutritionally balanced vegetables: low in calories and sodium, no fat or cholesterol, a good source of potassium, fiber and vitamins A, C, E, B6, folate, and thiamin. It also contains glutathione, another potent antioxidant with anticarcinogenic activity.
Asparagus is dioecious (having separate sexes) with female and male plants. For production, there are a number of advantages of male plants over females.
- Male plants do not produce fruits that divert resources from the crowns and roots, so they out-yield female plants over time.
- The yield advantage of an all-male field becomes increasingly apparent after the second or third year of production.
- Male plants emerge earlier in spring than female.
- Female plants have a tendency to lodge in heavy rain and strong wind as their fruits increase the weight of the plant. Male plants are less likely to lodge under the same conditions.
- Male plants have no seeds that can produce unwanted volunteer seedlings. Generally, volunteer seedlings are inferior to elite F1 hybrids and compete with F1 hybrid plants for nutrients.
Health benefit elements
Another goal of the breeding program is to increase the chemicals with health benefits of the hybrids. Asparagus is a rich source of protodioscin. It has been discovered that protodioscin is a potent inhibitor of a number cancer cell lines. It has also been reported that the steroid core of protodioscin, diosgenin, is quite effective in reducing cholesterol level in laboratory animals. Asparagus is also a rich source of rutin, a strong antioxidant. Certain hybrids with higher protodioscin have been developed.
Chemicals associated with disease resistance
Rutgers researchers found that protodioscin isolated from asparagus was an effective inhibitor of a number of pathogens. As there are variations among breeding lines in resistance to Fusarium diseases, scientists are investigating whether the variation in resistance can be correlated with specific chemicals in asparagus. Disease resistance and tolerance in perennial asparagus requires multiple generations of screening and trialing.
They have also found that the composition of fatty acids of plants can affect disease resistance. Plants with elevated palmitoleic acid (16:1) display enhanced resistance to a number of fungal diseases including tomato powdery mildew caused by Erysiphe polygoni, tomato Phytophthora blight caused by Phytophthora, and eggplant Verticillium wilt caused by Verticillium dahliae. Scientists are now examining the fatty acid profiles of asparagus lines with different levels of disease resistance against a few of the more serious diseases.