Production of gynogenic plants from hybrids of Allium cepa L. and A. roylei Stearn

Allium roylei is a non-bulbing wild relative of common onion (Allium cepa) with several desirable traits, including resistance to Botrytis leaf blight (BLB) and downy mildew. We obtained gynogenic plants by culturing flower buds from two A. cepa lines and several generations of plants derived from crosses of A. cepa and A. roylei. The donor plants used showed substantial differences in response to induction of gynogenesis. We obtained 59 plantlets from responsive A. roylei-derived plants. Backcross generations of A. roylei-derived plants (BC1F1 and BC1F2) provided the majority of the gynogenic plantlets; plants from earlier generations (F-1 and F-2) showed either very low or no gynogenic response. About half of the gynogenic plantlets continued to grow into plants. Flow cytometry revealed that most gynogenic A. cepa plants (86%) were haploids, while 9% were spontaneous diploids. In contrast, 77% of the gynogenic plants from A. roylei-derived plants were spontaneous diploids. Two gynogenic plants obtained from a BC1F1 and one from a BC1F2 plant produced small or medium size bulbs that dried down like A. cepa material; the remaining gynogenic plants produced non-dormant bulb-like structures. The possible contributions of doubled haploid A. roylei-derived plants to onion breeding are discussed. (C) 2003 Elsevier Ireland Ltd. All rights reserved.