Polyembryony

Polyembryony is the occurrence of more than one embryo arising from a single fertilization event or from the same fertilization process. It can lead to two or more embryos developing within a seed, egg, or similar structure, and may result in multiple offspring that are genetically related to the same parent.

There are several forms of polyembryony. Zygotic polyembryony refers to multiple embryos that originate from a single zygote, typically through cleavage events during early development. Nucellar polyembryony occurs when embryos form from nucellus tissue without fertilization, producing clonal seedlings that are genetically identical to the mother plant. Adventitious or somatic embryony describes embryos arising from somatic tissues outside the reproductive line, often also yielding clones.

In plants, polyembryony is observed across diverse groups, including some gymnosperms and angiosperms. It has particular agricultural relevance in Citrus, where nucellar embryony can produce clonal seedlings and influence seed formation. Mango and avocado species also display forms of polyembryony, sometimes contributing to the mix of zygotic and nucellar embryos within fruits or seeds. In conifers and other seed plants, polyembryony has been documented in certain species and may affect seed development and germination.

In animals, polyembryony has been documented in several taxa. Notably, some parasitoid wasps produce many embryos from a single egg, a form known as embryonic polyembryony. The nine-banded armadillo is a well-known example of monozygotic polyembryony, where a single zygote can split to form multiple genetically identical offspring.

Polyembryony is of interest for understanding developmental biology, reproductive strategies, and agricultural propagation, as it can influence genetic diversity and propagation outcomes.