Following multi-year evaluations, University of California researchers recently showcased their findings on four mandarin orange cultivars with growers at a field day at the Lindcove Field Station.

Tracy Kahn, curator of the experimental tree collections at the station, said the mandarins demonstrate potential for release. They are among the most interesting, she said, since the Gold Nugget, released in 1999.

Called TDEs because of their parentage of Temple, Dancy, and Encore varieties, they have desired large size, seedlessness, and reddish-orange rinds. Other desired traits include ease of peeling, good flavor, and little tendency to alternate-bear.

The triploid crosses were developed by Mikael Roose at UC, Riverside as part of the citrus variety improvement program there. The original crosses themselves were made by Susan Cameron, another UC citrus breeder now retired.

TDE2 and TDE3 may be released from the program this year or next, pending decisions on UC proposed international and domestic licensing procedures for new citrus varieties. The California Citrus Research Board held meetings in April and May to collect industry comments.

At its July 19 meeting in Ventura, the board is to consider the recommendations, developed from written and verbal comments, of its New Varieties Licensing Committee.

Industry comment

Ted Batkin, president of the board at Visalia, in soliciting industry comment, said, “There are major elements in the proposals which if adopted will represent a significant departure from the past, both in practice and in philosophy. It is very likely that they would be precedent-setting, and those precedents would impact other commodities.”

Under consideration is a plan for the UC Office of Technical Technology Transfer to license a grower-based, non-profit organization to distribute the tree and develop a program to promote the TDE cultivars under a trademarked name.

It could include both a tree royalty, now the standard, and a portion of f.o.b. fruit sales, or production royalty, collected annually. Both fees would be split by the university and the non-profit entity. The proceeds would be used for promotion campaign and cultural practices research.

“At this time,” Kahn said, “there's great excitement in the industry for mandarin oranges. We would like them to have several traits but from evaluations we know there is no perfect mandarin. Some may have several but not all the characteristics.”

Licensing proposal

She said the consideration of a licensing proposal is a groundbreaking event. “One of the problems when a variety like Gold Nugget is released from the university, there is no one in charge of marketing it.”

Kahn, whose evaluations are independent of Roose's breeding work, went on to say that with the many mandarin varieties available, it would be good for some entity to take ownership of new varieties so the California industry can benefit from them. Possibly new varieties could be licensed elsewhere in the U.S. and in foreign countries.

Kahn's evaluations were made from fruit produced by trees at Lindcove, Riverside, Irvine, and Thermal. She emphasized that a single variety will have different qualities according to where it is grown. “And that's why it is important to evaluate them in several locations.”

Kahn has also been evaluating late navel cultivars with the help of cooperating growers at nine sites from Madera to Fillmore. From the first four years of data from the six-year program, Summer Gold stands out in higher average solids-acid ratios but is not as late as others in the group including Autumn Gold, Chislett, Powell, Late Lane, and Barnfield.

Summer Gold, however, tends to have softer rind than the others, and also ranked first in peelability.

She continues to evaluate early navel selections, including Early Beck, Fisher, Fukumoto, Sweet Martin, and Washington. Fisher and Early Beck tend to be earlier maturing, while Fukumoto and Sweet Martin develop bright rind color earlier.

The Australian origins of early navels, she noted, underscores the need for them to be tested in various locations in California.

Kahn is also curator of the Citrus Variety Collection at UC, Riverside, established in 1917 with citrus and related plants from Ribidoux, the original site of the citrus experiment station.

The CVC collection includes 28 of 33 citrus and citrus-related genera, making it one of the most extensive of its kind in the world. Studies there have also been significant in breakthroughs ranging from rootstocks tolerant to citrus tristeza disease to mapping the citrus genome.

e-mail: dan_bryant@intertec.com