Abnormal transition from meiosis I to meiosis II induces male sterility in a seedless artificial hybrid of citrus.

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Male sterility is an important trait for breeding and for the seedless fruit production in citrus. We identified one seedling which exhibiting male sterility and seedlessness (named hereafter), from a cross between two fertile parents, with sour orange () as seed parent and Ponkan mandarin () as pollen parent. Analysis using pollen viability staining, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that the mature pollen of the was aborted, displaying collapse and deformity. Further cytological analysis identified the abnormal formation of monad, dyad, and tetrad instead of the normal tetrad formation, leading to meiotic failure in the seedless hybrid. By comparative transcript profiling of meiotic anther of fertile and sterile hybrids, we observed significant downregulation of () and genes in the hybrid, which known to control the transition from meiosis I to meiosis II in plants. These results indicated abnormal meiosis led to the male sterility of the seedless hybrid and that the decreased activities of kinases and cyclins may associated with the failure of the transition of meiosis I to meiosis II during anthers development.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11032-024-01521-5.