Apomixis: Mechanism, Genetic Basis and its Significance in Horticultural Crops

Abstract

Apomixis, which allows seeds to form asexually without undergoing meiosis or fertilization, holds great promise for agricultural biotechnology by facilitating the generation of maternal clones that preserve favorable traits in crops. There are two primary types of apomixis: gametophytic and sporophytic, which are differentiated by whether the embryo originates from the embryo sac or directly from diploid somatic cells. In gametophytic apomixis, embryo sacs are formed via mitosis rather than meiosis (apomeiosis), followed by embryo development without fertilization (parthenogenesis). In contrast, sporophytic apomixis involves the formation of embryos from somatic cells, while still relying on the sexually derived embryo sac for endosperm development. The genetic regulation of apomixis is complex, involving several loci with restricted recombination, often linked to heterochromatic regions. Key aspects of apomixis, such as the avoidance of meiosis, parthenogenesis, and the development of endosperm without fertilization, are controlled by distinct genetic loci. Recent progress has highlighted crucial genetic areas like the Apospory-Specific Genomic Region (ASGR) in Pennisetum that are linked to apomictic processes. Synthetic apomixis, which involves the engineering of pathways for apomeiosis and independent embryo and endosperm development, emerges as a promising avenue for enhancing crop breeding efforts.