The characteristics of gametogenesis may contribute to the partial female-fertility in aneuploid Lilium

Unlike most aneuploid plants which are usually seedless, aneuploid lilies (Lilium), have partial female-fertility regardless of their male sterility. However, the underlying mechanisms remain unclear. ‘Chen Xi’, as an example of aneuploid lilies, was investigated for its gamete formation and fertility using modern cytogenetic methods. It had 44 chromosomes, consisting of 35 A-chromosomes and 9 L-chromosomes. Many irregular meiotic characters, such as trivalents, univalents, lagging chromosomes and micronuclei, were commonly observed. It produced functional eggs with variable chromosomes ranging from 19 to 48 among the analyzed nine progenies, indicating that it had partial female-fertility regardless of male sterility. However, the chromosome numbers in the secondary nuclei of embryo sacs produced by ‘Chen Xi’ were invariable twice those of its somatic cells. This was the first time to confirm the derived principle – Each aneuploid Lilium produces variable chromosomal eggs and invariable chromosomal secondary nuclei in its embryo sacs. The principle would be associated with the partial female-fertility regardless of male sterility of aneuploid lilies. Fluorescence in situ hybridization first confirmed the derived principle - Each aneuploid lily produces variably chromosomal eggs and invariably chromosomal secondary nuclei in its embryo sacs.