Asexual reproduction through seeds: the complex case of diplosporous apomixis

Abstract

Apomixis is considered a potentially revolutionary tool to generate high-quality food at a lower cost and shorter developmental time due to clonal seed production through apomeiosis and parthenogenesis. In the diplosporous type of apomixis, meiotic recombination and reduction are circumvented either by avoiding or failing meiosis or by a mitotic-like division. Here, we review the literature on diplospory, from early cytological studies dating back to the late 19th century to recent genetic findings. We discuss diplosporous developmental mechanisms, including their inheritance. Furthermore, we compare the strategies adopted to isolate the genes controlling diplospory with those to produce mutants forming unreduced gametes. Nowadays, the dramatically improved technologies of long-read sequencing and targeted CRISPR/Cas mutagenesis justify the expectation that natural diplospory genes will soon be identified. Their identification will answer questions such as how the apomictic phenotype can be superimposed upon the sexual pathway and how diplospory genes have evolved. This knowledge will contribute to the application of apomixis in agriculture.

Keywords: Apomixis; breeding; clonal progeny; diplospory; flowering plants; gametophyte; meiosis; reproduction; sporogenesis; unreduced gametes.