Scientists Crack Avocado Mystery After Decades of Study

Scientists just solved a botanical riddle that's puzzled experts for decades: why avocado trees switch between male and female throughout the day.

Researchers at UC Berkeley and UC Riverside identified a single gene called SDMYB that controls the remarkable daily sex changes in avocado flowers. The trees act as hermaphrodites, with flowers releasing pollen (male) at certain times and receiving it (female) at others.

About half of avocado trees are "A-types" that open female flowers in the morning and male flowers in the afternoon. The other half are "B-types" that do the opposite. This clever natural system prevents trees from pollinating themselves and keeps the gene pool diverse.

The discovery, published in the Proceedings of the National Academy of Sciences, solves a practical headache that's cost California's $500 million avocado industry years of lost time. Breeders working to create better varieties by combining traits like taste, size, and weather resistance had to wait over a decade just to see a tree's first flowers and learn its type.

"This gives us a shortcut we've never had before," said Eric Focht, a staff research associate from UC Riverside who co-authored the study. Instead of waiting years, breeders can now identify a tree's flower type almost immediately using DNA testing.

The research team analyzed the genomes and flowering patterns of hundreds of trees to pinpoint the gene responsible. Jeffrey Groh, the study's first author and a postdoctoral researcher at UC Berkeley, called it "super exciting to lift the hood on this remarkable example of the diversity of sexual reproduction strategies in plants."

The Ripple Effect

The timing couldn't be better for California growers. Climate change is scrambling plant signals, causing avocados and other crops to flower earlier than normal as they respond to unseasonable heat. Understanding the genetic controls behind avocado flowering will help breeders develop varieties better suited to changing growing seasons.

Graham Coop, a UC Davis professor of evolution and ecology who co-authored the paper, explained that this knowledge will help the industry adapt. Breeders can now make smarter decisions about which trees to cross, speeding up the development of resilient varieties that can thrive despite unpredictable weather patterns.

For California farmers who carefully plant mixtures of A-type and B-type trees to ensure good pollination, the discovery means faster innovation and stronger orchards ready for whatever climate challenges lie ahead.