Seedlessness is a most valuable trait in fruit crops for fresh consumption and processing. The mutations in essential meiosis genes are known to confer sterility and seed abortion in plants. However, defects in meiosis have rarely been reported in fruit crops. Here, we found meiosis defects caused sterility in a seedless citrus bud sport cultivar, with massive unpaired univalents during diakinesis, indicating a disruption in crossover formation. A non-functional CrMER3A