Groundbreaking discovery could remake California’s avocado breeding

Even as a fixture in California cuisine and a sizable industry for the state’s farmers, avocados have presented an ongoing mystery for scientists: How do they easily flip sexes?

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In a new study published in the journal Proceedings of the National Academy of Sciences, California researchers have finally answered that question by tracing the process in avocado trees back to a single gene.

“Even for a plant that is so familiar to us, there’s been this great mystery for so long,” Jeffrey Groh, a postdoctoral researcher at UC Berkeley and first author of the study, told SFGATE. “It’s super exciting to lift the hood on this remarkable example of the diversity of sexual reproduction strategies in plants.”

In California, where avocados are the and the industry value is about $500 million, the find will be an immediate advantage for breeders trying to create the best varieties.

The flowers of avocados trees, which are hermaphrodites, act either as male by releasing pollen or as female by receiving it. About half of the trees, so-called A-types, open female flowers in the morning and male in the afternoon. B-types do the opposite. The phenomenon naturally prevents the trees from self-pollinating and inbreeding. And on farms, growers carefully plant a mixture of A-types and B-types in their fields, since they easily pollinate each other.

The problem has been for breeders, who are trying to bring together desirable qualities like taste, size, number of fruits and resilience to weather. It can take over a decade before an avocado plant produces its first flowers, meaning breeders had to wait years before they knew which were type-A and which were type-B.

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“This gives us a shortcut we’ve never had before,” Eric Focht, a staff research associate from UC Riverside and co-author of the study, said in a statement. “Instead of waiting years for a tree to flower, we can identify its flower type almost immediately using its DNA. That allows us to make much smarter breeding decisions.”

The researchers analyzed the genomes and flowering behavior of hundreds of trees to discover the single gene, SDMYB, was responsible for the trees’ flower schedule.

Graham Coop, an evolution and ecology professor at UC Davis who co-authored the paper, told SFGATE that the findings could help to make the industry more resilient.

“In today’s climate, plants are getting scrambled signals, and they’re flowering early in the year because they’re getting like the heat signals earlier,” Coop said. “Having a better understanding of the flowering of avocados will help people understand how climate change will impact the growing season of these plants and how to breed for a better growing season.”