Aborted anthers, which are the most severe form of male-sterility in Citrus, were presumed to be due to gene-cytoplasmic interaction. However, owing to the absence of detailed crosses, this has not been confirmed. In this study, we confirm that aborted anthers are caused by gene-cytoplasmic interaction.
Cross breeding between heterozygous for male fertility cultivars was conducted. When ‘Kuchinotsu No. 20’ (‘Kiyomi’ tangor x ‘Trovita’ orange) was crossed with ‘Otani iyokan’, 8 out of 26 seedlings had aborted anthers. This segregation of male sterility/fertility fitted the expected 1:3 ratio (χ2 = 0.462). However, no seedlings had aborted anthers in the reciprocal cross ‘Otani iyokan’ x ‘Kuchinotsu No.20’, or a ‘Miyauchi iyokan’ x ‘Page’ cross. These results indicate that aborted anthers in Citrus are controlled by the interaction between nuclear and cytoplasmic genes (gene-cytoplasmic male sterility), and that ‘Kuchinotsu No. 20’ has sterile cytoplasm. A genetic basis for the inheritance pattern is discussed.