University of California researchers build a better avocado tree

A new kind of avocado — created by UC Riverside researchers — may be appearing in grocery stores in coming years.

The Luna UCR avocado will soon be marketed to growers worldwide, though it will be a little longer before you can buy it at the supermarket.

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The result of decades of research, the Luna tastes similar to the popular Hass avocado, which dominates the U.S. market. But important differences — including its compact tree shape and flower type that can pollinate other avocado trees — may set it apart for growers and others in the industry.

UCR’s avocado-breeding program, which has been operating about 70 years, partnered in 2020 with Eurosemillas, a Spain-based agricultural commercialization group that has worked with the University of California since 1989, according to its website.

Eurosemillas has joined with growers in 14 other countries to grow the Luna, a UCR news release from July states.

It’s not unusual for UCR or other public institutions to create new plant varieties for the industry or general public, Eric Focht, a UC Riverside staff research associate in the Botany and Plant Sciences Department, said in Wednesday, Aug. 16 email.

Other plants created by UCR, including avocados, citrus and asparagus, are examples.

But, he said, there has been a decline in publicly funded breeding efforts in recent decades, perhaps because of the short-term cost.

It takes about two decades to release a new plant variety that was initially planted from seed, and “that’s not a fast turnaround,” Focht said.

The Luna avocado was a long time in the making.

Berthold “Bob” Orphie Bergh, who was described as UCR’s “first real long-term avocado breeder” by Mary Lu Arpaia in a UCR news release, began avocado research in the 1950s.

Arpaia is a UC Cooperative Extension professor in subtropical horticulture, and one of the researchers on the Luna UCR patent, alongside Focht, Bergh and others.

“A really important point is that when you have a breeding program, especially for tree crops, you build upon the success of your predecessors,” Arpaia said Wednesday, Aug. 9.

Bergh initially sought an alternative to the Fuerte avocado, the country’s most popular type at the time, which Arpaia said had production problems such as erratic fruit-bearing and a sprawling tree shape. There was already an alternative, the Hass, but it was unpopular with consumers because the skin turns black when it’s ripe, the UCR release states.

By 1983, Bergh had created the Gwen avocado, which stays green — but by then, consumers had grown accustomed to the Hass avocado, with the help of marketing and technology that allowed for more uniform ripening.

In search of future varieties, in the mid-1980s, Bergh planted up to 70,000 avocado seeds from Gwen mother trees, according to UCR.

Several new varieties emerged from that batch of seeds. Luna will be the last of them to be released, Arpaia said.

The Hass avocado is named after its creator, Rudolph Hass, and the Gwen avocado takes its name from Bergh’s wife. The Luna is named after Arpaia’s dog.

“We were having trouble coming up with a name,” she said.

One day, while brushing Luna, “a lightbulb went off.”

To consumers, the Luna avocado will seem similar to the Hass variety.

Hass avocados currently account for 95% of the avocados in the global market, Focht said.

While their shapes differ slightly, the Hass and Luna avocado have green skins that turn black when ripe, and Focht said the Luna’s taste is “very Hass-like.”

Apple varieties are a good analogy for the way different avocados taste, Arpaia said.

“You go to the store and you see all these varieties of apples, and they all taste like apples, but they’re subtly different,” she said.

The difference between avocado varieties is a little more subtle, she said, though they “vary quite a bit in texture.”

The Hass is creamy, she said, the Luna UCR is very smooth and the Gem is meatier.

The avocado fruit is one consideration for researchers. The tree is another.

In a sunny avocado field near UCR, Focht pointed out the different shapes that make trees more or less desirable to growers.

“We’ve traditionally been looking at something like a narrow cylinder or column as sort of the ideal tree shape,” Focht said.

More upright, compact trees, like the Luna, take up less space, meaning that more can be planted in a given field.

Carl Stucky, a California Avocado Society board member and an agricultural consultant, said Tuesday, Aug. 29, that the tree’s shape has benefits for “higher-density planting.” 

There are other considerations as the industry explores new directions, such as using trellises, Focht said. While researchers don’t know yet how the Luna would behave in that situation, Focht said that “we suspect it should do well,” and trials are planned.

“There’s lots of different situations that a field can present, and so it probably is the case that not one single variety is gonna fit all of those,” Focht said, but the Luna is “the perfect fit for what we’ve been focusing on for some 50 to 60 years.”

Another potential benefit of the Luna is its flowers.

Avocado trees have one of two flower types, and will cross-pollinate with trees with the opposite flower type, Focht said.

The fruit of the avocado tree variants being planted today to cross-pollinate Hass avocado trees don’t have much market value, Focht said. That means that the 10% to 11% of a field that is taken up by those variants often goes to waste, because it could cost more to pick the fruit than a grower would make by selling it.