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

To develop the male sterile line of Allium fistulosum L., cytoplasmic Subst itution by continuous backcrossing was performed using A. galanthum Kar. et Kir. as a cytoplasm donor-Pollen and seed fertility in F-1 hybrid and the backcross progenies were examined. In backcrossing, progenies were selected in the direction of high seed fertility from BI generation and in the dire ctions of low and high pollen fertility from B-2 generation. The pollen fertility in F-1 hybrid was 65 %; that in B-1 and B-2 generation s varied from 10 to 77 %, 0 to 98 %, respectively. Almost all plants in B-3 , B-4,and B-5 generations selected in the direction of low pollen fertility were pollen sterile. The decrease of pollen fertility in F-1 hybrid is att ributed to the hybridity of nuclei. However, it is difficult to relate poll en sterility observed in the backcross progenies to the hybridity of nuclei because the nuclei of those plants are mostly composed of genomes of A. fi stulosum. Therefore, it is concluded that the pollen sterility observed in the backcross progenies is attributed to incompatibility between the cytopl asm from A. galanthum and the nucleus from A. fistulosum. In each of B-3, B -4, and B-5 generations selected in the direction of high pollen fertility, pollen fertile and pollen sterile plants segregated at a ratio of approxim ately 1 to 1. This finding strongly indicates that the pollen fertile plant s had a single dominant fertility restoring gene which originated from the nuclear genome of A. galanthum and that the pollen sterile plants had not t his gene. Although the seed fertility somewhat varied among the progenies a t each backcross generation, it could be improved with frequency of backcro ssing, and some plants had higher seed fertility than A. fistulosum. Analys es of chloroplast and mitochondrial DNAs proved that all the backcross prog enies examined inherited the cytoplasm from A. galanthum. From these result s, we conclude that the cytoplasm of A. galanthum is useful for developing the male sterile line of A. fistulosum.