Hundreds of avocado genomes and hour-by-hour observations of thousands of flowers led researchers to SDMYB, a single gene whose activity controls whether trees follow A- or B-type flowering schedules.
Two SDMYB variants explain the split: A-type trees carry one of each allele, while B-type trees carry two recessive copies, solving a pollination puzzle that had stumped botanists for more than a century.
10 to 15 years is how long breeders previously had to wait for trees to flower before identifying type; the new genetic markers let them sort seedlings much earlier and cut time, labor and orchard space.
California orchards often plant about 10% B-type pollinizers to boost nearby A-type trees, even though B-type fruit is less commercially desirable than Hass, making early identification immediately useful.