Researchers at the University of California, Davis, have discovered a genetic switch that controls the alternating daily pollination rhythm of avocado trees. Traced back 42 million years, this single-gene variation solves a century-old agricultural mystery and promises to drastically shorten the multi-year timeline required for breeding new varieties.
Avocado trees possess a unique biological system to prevent inbreeding. While every tree is a hermaphrodite, their flowers alternate between functioning as male and female at different times of the day. Roughly half of all avocado trees, known as A-type plants, open their female flowers in the morning and their male flowers in the afternoon. B-type plants follow the exact opposite schedule.
This partitioning creates a reliable system for cross-pollination. Historically, avocado farmers usually try to plant a mixture of A- and B-type trees in the same orchard so that bees and other pollinators have access to active pollen and receptive flowers throughout the entire day. Without this natural staggering, synchronised flowering across all trees would prevent successful pollination entirely.
Unlocking the SDMYB Gene and a 42-Million-Year-Old Rhythm
Until recently, the exact biological trigger behind this daily pollination choreography remained unknown. To pinpoint the mechanism, a research team analyzed the genomes of hundreds of avocado trees grown by collaborating scientists at University of California, Riverside. By comparing genetic variations against the recorded flowering behaviour of each tree, investigators isolated a single gene called SDMYB.
Evolutionary analysis indicates this specific genetic switch developed approximately 42 million years ago. Researchers note that the finding sheds light on ancient botanical adaptations.
The discovery moves plant science past simple observation of daily floral opening and closing. Through the power of genetics, we can detect traces of this rhythm far into the ancient past,
Groh added.
Cutting Years Off Avocado Breeding Cycles
Beyond its evolutionary significance, the identification of the SDMYB gene offers practical utility for commercial growers and agricultural researchers. Developing new commercial avocado varieties has long been hindered by a frustrating biological timeline.
Avocado plants typically take anywhere from 10 to 15 years to flower for the first time. Before this genetic breakthrough, breeders had no way of knowing whether a young seedling would mature into an A-type or B-type tree until the plant finally flowered years later.
“This has been a major impediment for avocado breeders. Previously, you could not tell whether a plant was an A- or a B- type until it flowered, and avocado plants may take up to 10 or 15 years to flower in the first place.”
Graham Coop, professor of evolution and ecology at UC Davis
The newly identified genetic markers allow researchers to bypass the lengthy waiting period entirely. By screening seedlings in a lab setting, growers can identify flower types at the earliest stages of development.
Immediate Application for Orchard Yields
The findings, published in the Proceedings of the National Academy of Sciences, provide a direct framework for sorting seedlings to maximize orchard productivity and tailor planting ratios. Because the markers operate at the DNA level, researchers emphasize that the tool requires no trial-and-wait phase.
Coop noted, pointing out that these genetic markers will greatly speed up avocado breeding and research.
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