New asparagus varieties show promise for yield, quality

University of California plant breeders are already working with promising experimental asparagus varieties that perform better in trials than their new variety that was released just three years ago.

A number of the experimental varieties have yielded more in trials than DePaoli, which was a 2005 UC release. These varieties are particularly promising in their yields of the highest quality asparagus spears that command a premium in some export markets.

But it will take years to travel the long road from these promising preliminary trials to the release of new asparagus varieties.

"It will be at least three years before any of these experimental varieties is released because we want to see it in larger scale grower trials as well," said Neil Stone, UC Riverside asparagus breeder.

Stone said he has seen the results of five years of harvest of the promising varieties in Riverside. But trials of the experimental varieties have only been in the ground in San Joaquin County long enough for one harvest.

It takes years to sort out the meaning of dozens of trials and come to sound conclusions about which new varieties are most worth advancing, he said.

When Stone began working at UC Riverside in asparagus breeding in 1991, DePaoli was already in trials. But this latest new variety was not released until 2005.

"We're now at the point where we have substantial amounts of DePaoli seed," Stone said.

There has been generally good news in the reports from growers who were the first to plant the new DePaoli variety.

Four growers with a 267 acres of DePaoli have already responded to the survey sent out by the California Asparagus Commission.

The incidence of fusarium or phytophthora in fields with DePaoli have ranged from less than 5 percent to no higher than 15 percent in any of these fields.

"This has been encouraging news," Stone said.

But even after all these years the results in trials comparing DePaoli with the previous standard are mixed.

"In most trials DePaoli has beaten UC 157 but not at the latest trial on McDonald Island," said Brenna Aegerter, UC Cooperative Extension farm advisor in San Joaquin County.

While growers are just beginning to try DePaoli, trials are already under way on the next advance in asparagus.

The best five-year yields in the trial planted at Riverside in 2002 have come from the numbered hybrid with MCE4 as the male parent and F132 as the female parent.

In that trial, this numbered variety has yielded even more asparagus than DePaoli. The yield bonus has been even greater when these varieties are harvested daily, rather than three times a week.

The experimental variety has also produced an extraordinary yield of spears that meet the important export quality standard.

"This particular variety in Riverside has given more than half its yield in export quality spears," Stone said.

One key standard in asparagus trials is the amount of the harvest that is of export quality—spears that are between seven-sixteenths and ten-sixteenths of an inch in diameter, green, tight, with tapered heads and no defects.

Export quality essentially refers to that demanded by the Japanese, who have very high and strict standards for their asparagus and are willing to pay a premium for product that meets them.

In another trial planted at Riverside in 2003, the highest four-year yields have come from the numbered hybrid with MCE4 as the male parent and F582 as the female parent.

This experimental variety has maintained a very slight yield edge over DePaoli in this trial. But the bonus in export quality spears has been greater. And both DePaoli and the experimental variety have yielded substantially better than UC 157, which was the previous industry standard.

These results are very promising.

But an experimental variety has a long road to travel between preliminary trials in one location to release for commercial use by growers throughout the state.

While trials of future varieties that could produce good yields of the highest quality spears continue, work has already begun on the next generation of asparagus.

Preliminary research is under way on future varieties that will allow California growers to meet the low cost competition by harvesting asparagus mechanically.

"One of our long-range goals is to develop an asparagus variety that is easier to harvest mechanically," Stone said.

This work will focus of developing varieties with a plant architecture suited to machine harvesting, and with spear regrowth patterns that would be suitable for repeat mechanical harvests.

(Bob Johnson is a reporter in Magalia. He may be contacted at bjohn11135@aol.com.)