UC Riverside researchers release new variety of asparagus

DePaoli asparagus offers a higher yield of spears than other varieties of the vegetable

UC Riverside researchers have released a new variety of asparagus that offers a higher yield than previous varieties of the vegetable and boasts an excellent spear quality, marked by a high percentage of marketable spears. Higher yield of marketable spears reduces the impact of high land and labor costs, thereby making the asparagus more profitable without raising consumer prices.

Named “DePaoli” after William P. DePaoli, the first manager of the California Asparagus Commission who long supported the asparagus breeding program in the state, the superior hybrid marks the third time that UCR has released a new variety of the vegetable, the most recent being 1982.

“Particularly now, the asparagus industry in this country needs new varieties of the vegetable – varieties that can compete with those produced in other countries where labor cost is low, such as Peru and Mexico,” said Mikeal Roose, a professor of genetics in the Department of Botany and Plant Sciences and the leader of the asparagus breeding project. “Indeed, Neil Stone, a staff research associate at UCR, and I are working on other promising hybrids that are in trial at the moment, some of which may have even better yields than DePaoli.”

Currently, UCR is cultivating the DePaoli variety in a field near campus. The first test of the new variety, which involves evaluation of yield, spear quality, and other traits, was started in 1990. A full harvest of DePaoli was obtained three years after planting. To ensure that the new variety was not susceptible to disease, it was then harvested for a few additional years.

“DePaoli has gone through at least a dozen trials, but we need to keep the trials going for a while longer because it may be affected by weather or diseases that only occur occasionally,” Roose said. “It will take several years before significant amounts of this new variety appear in the market.”

Asparagus, a perennial vegetable, has both male and female plants. In the case of DePaoli, first a male parent and a female parent are selected for their good characteristics including spear size, spear quality, yield, and disease tolerance. Next, these plants are crossed and the resulting hybrids are evaluated for yield, spear quality and other essential traits. When two parents that produce good hybrid offspring have been identified, a large number of the male and female parent plants are produced by cloning using tissue culture methods. The male and female plants are then planted in an isolated field. Bees pollinate the females, leading to seed production. These seeds are then sold and planted by farmers who produce the spears consumers eventually will buy. “The first commercial harvest of seeds has only just been completed,” Roose said.

DePaoli asparagus is similar in taste to previous varieties of asparagus. Currently, the UCR research team is working on producing improved varieties of the vegetable by incorporating new approaches in their research.

“One path we may take is to identify ’supermale’ plants that produce only male offspring when hybridized with a female. Such male varieties are used in Europe and other parts of the US, but have not been successful in California,” Roose said. “Male plants produce more spears than female plants because the latter expend energy in order to produce seeds, resulting in lower yields. For male varieties to be successful, we must identify a supermale that produces hybrids with good quality spears. Another current activity for our research is to incorporate tools from molecular genetics to improve the efficiency of asparagus breeding.”

Asparagus, which is a Greek word meaning stalk or shoot, grows best in sandy, well-drained soils. The plant can be productive for 15 years or more. Asparagus spears grow from a crown – the root system of an asparagus plant that is grown from seed. The crown is planted about a foot deep in sandy soils. Spears grow from buds in the crown, and, if not harvested, branch out to form the “fern” which is the feathery green leaves and stems of the plant. Spears are not usually harvested until plants are two years old in order to allow the crown to become large and healthy. During spring and the early summer of the third year, the crown produces spears, which are harvested for about 6-9 weeks.

A nutrient-rich food, asparagus was cultivated first more than 2,000 years ago in the eastern Mediterranean region. It was first planted in California in the 1850s.