Apomixis in Agriculture
Definition: Asexual seed production without fertilization.
Agricultural Value:
- Maintains hybrid vigor (heterosis) across generations — seeds saved from hybrid crops can replant successfully
- No need for repeated parental crossing each season (reduces cost)
- Produces genetically uniform offspring (clones)
Mechanism: Embryo forms from diploid nucellar cells or unreduced egg cells — no meiosis, no fertilization
Example: Citrus (nucellar embryony produces polyembryonic seeds — multiple embryos per seed, each genetically identical to the parent)
Parthenocarpy in Agriculture
Definition: Fruit development without fertilization → seedless fruits
Agricultural Value:
- Commercially important seedless fruits: banana, seedless grapes, seedless watermelon
- Better consumer preference (no seeds = easier consumption)
- Induced artificially by gibberellins or auxins
Key Distinction: Parthenocarpy ≠ Apomixis
- Parthenocarpy = NO seeds (no fertilization, ovary grows without seed formation)
- Apomixis = Seeds WITHOUT fertilization (seeds exist, but no sexual fusion)
Polyembryony
Definition: More than one embryo per seed
Types:
- Nucellar polyembryony (adventive) — nucellus cells develop into additional embryos (e.g., Citrus)
- Cleavage polyembryony — zygote splits
- Multiple fertilizations
Agricultural Significance: Citrus seeds are polyembryonic — multiple seedlings from one seed; nucellar seedlings are disease-free clones