Cytoplasm of a wild species, Allium galanthum Kar. et Kir., is useful for developing the male sterile line of A. fistulosum L

摘要

To develop a male sterile line of Allium fistulosum, cytoplasmic substitution by continuous backcrossing was performed using A. galanthum as a cytoplasm donor. Pollen and seed fertility in F1 hybrid and the backcross progenies were examined. In backcrossing, progenies were selected in the direction of high seed fertility from the BC1 generation and in the directions of low and high pollen fertility from BC2 generation. The pollen fertility in F1 hybrids was 65%; that in BC1 and BC2 generations ranged from 10 to 77% and 0 to 98%, respectively. Almost all plants in BC3, BC4, and BC5 generations selected in the direction of low pollen fertility were pollen sterile. The decrease of pollen fertility in F1 hybrids is attributed to the hybridity of nuclei. However, it is difficult to relate pollen sterility observed in the backcross progenies to the hybridity of nuclei because the nuclei of those plants are mostly composed of genomes of A. fistulosum. Therefore, it is concluded that the pollen sterilityobserved in the backcross progenies is attributed to incompatibility between the cytoplasm from A. galanthum and the nucleus from A. fistulosum. In each of BC3, BC4 and BC5 generations selected in the direction of high pollen fertility, pollen fertile and pollen sterile plants segregated at a ratio of approximately 1:1. This finding strongly indicates that the pollen fertile plants had a single dominant fertility restoring gene which originated from the nuclear genome of A. galanthum and that the pollen sterile plants did not possess this gene. Although seed fertility varied somewhat among progenies at each backcross generation, it could be improved with frequency of backcrossing, and some plants had higher seed fertility than A. fistulosum. Analysesof chloroplast and mitochondrial DNAs proved that all the backcross progenies examined inherited the cytoplasm from A. galanthum. From these results, it is concluded that the cytoplasm of A. galanthum is useful for developing male sterile lines of A. fistulosum.