Abstract
Relationship between weight of seeds and ploidy level of the seed-derived plantlets obtained from reciprocal crosses between diploid ‘Banpeiyu’ pummelo and two tetraploid varieties were examined to efficiently select triploid progenies for further breeding of the pummelo. Percentages of fully developed seeds obtained from the cross of ‘Banpeiyu’ pummelo with 4X Yuzu or 4X Natsudaidai were decreased by 48.0% and 8.4% as compared with the control, respectively. Seedlings obtained from these two crosses included triploids, tetraploids and hexaploid. ‘Banpeiyu’ pummelo as seed parent yielded a high percentage of triploids (88.0%) when crossed with 4X Yuzu, but low percentage (30.2%) when crossed with 4X Natsudaidai. In both crosses, the average weight of triploid seeds was significantly lighter than that of tetraploid seeds. Furthermore, all seedlings derived from undeveloped seeds were triploids.
Percentages of fully developed seeds obtained from 4X Yuzu or 4X Natsudaidai × ‘Banpeiyu’ pummelo were not different from those of seeds from open pollinated fruits, but weights of these seeds were extremely decreased compared to seeds from open pollinated fruits. Approximately 50% of in vitro cultured seedlings obtained from both crosses were triploid, while the others were tetraploids, which might be derived from nucellar embryos of seed parents. There was no difference in the average weights of seeds between have seeds yielding triploid seedlings and those yielding tetraploids that might have originated from nucellar tissue.
