Possibility of developing a male sterile line of shallot (Allium cepa L. Aggregatum group) with cytoplasm from A-galanthum Kar. et Kir.

In an effort to develop a male sterile line of shallot (Allium cepa L. Aggregatum group), a continuous backcrossing was carried out using A. galanthum Kar. et Kir. as a cytoplasm donor and the shallot as a nucleus donor. Meiosis and fertility in the F-1 hybrids, B-1, B-2, and B-3 progenies were examined. The F-1 hybrids had low pollen fertility, whereas the B-1 plants were pollen sterile or nearly so; the B-2 and B-3 plants were completely pollen sterile. Pollen sterility observed in the backcross progenies was attributed to nuclear-cytoplasmic incompatibility because the pollen mother cells in most of these plants underwent normal meiosis. Although the seed fertility varied considerably among the progenies at each backcross generation, it could be improved with the advancement of backcrossing. PCR- RFLP analysis of chloroplast DNA proved that all the backcross progenies had the cytoplasm from A. galanthum. These results demonstrate that there is a realizable possibility of developing a male sterile line of shallot using this genetic approach.