Table 4.
Theoretical outcome of interspecific-interploidy crosses following paternal and maternal excess.
| Parental ploidy | Ploidy (m/p) | ||||
|---|---|---|---|---|---|
| Maternal (m) | Paternal (p) | Predicted endosperm ploidy (m/p) | Hybrid ploidy obtained (m/p) | ||
| Paternal excess (p) | 2x | 4x | 4x (2m:2p) | NH 1 | |
| Maternal excess (m) | 4x | 2x | Normal (reduced) embryo sac | ||
| 5x (4m:1p) | NH 2 | ||||
| Unreduced embryo sac 3 | |||||
| 9x (8m:1p) | 5x (4m:1p) | ||||
| Normal (reduced) embryo sac followed by zygote/embryo chromosome doubling 4 | |||||
| 5x (4m:1p) | 6x (4m:2p) | ||||
| Both endosperm and zygote/embryo chromosome doubling 5 | |||||
| 10x (8m:2p) | 6x (4m:2p) | ||||
2x: H. undatus, 4x: H. megalanthus.
1
NH - No hybrids were obtained from the H. undatus × H. megalanthus cross, even when we used an embryo rescue technique.
2
NH- No H. megalanthus × H. undatus allotriploids were obtained.
3
Assuming that all the embryo sac cells (including the egg cell) result from unreduced gamete formation, since megasporogenesis occurs before megagametogenesis.
4
Ploidy in the embryo sac cells was assumed to be reduced, while the allohexaploids are a result of chromosome doubling.
5
Chromosome doubling occurs in the endosperm and zygote/embryo, resulting in 10x and 6x, respectively.