Doubled haploid production in onion (Allium cepa L.): from gynogenesis to chromosome doubling

Abstract

Bulb onion ( Allium cepa L.) is an allogamous diploid (2n = 16) important for its culinary uses, nutritional value, and medicinal benefits. Despite its economic importance, onion yields and bulb quality are declining, emphasizing the need for new and improved strategies for maintaining and enhancing overall crop quality. Development of inbred lines in onion through traditional breeding is often difficult due to its biennial life cycle, inbreeding depression, and comparatively high heterozygosities. Moreover, genetic research in onion has been hampered by large nuclear genome size. In this regard, gynogenic doubled haploids promise several advantages over inbred lines in support of onion breeding programs and genetic studies. These include complete homozygosity in doubled haploid lines, reduced DNA methylation, elimination of deleterious alleles, and amenability to genetic analysis. This review focuses on the application of in vitro gynogenesis for producing doubled haploids in onion. Factors influencing haploid induction, methods for inducing chromosome doubling and ploidy assessment, evaluation of haploid progenies and doubled haploid lines, and features of doubled haploids potentially useful in crop improvement and genetic studies, are discussed. We identify four major limitations to the success and efficiency of in vitro gynogenesis in onion and discuss strategies for mitigating the negative impacts they pose. This review may be useful to research programs producing doubled haploids in onion or other Allium species using in vitro gynogenesis.

Original Research Production of Haploids and Doubled Haploids from Unfertilized Ovule Culture of Various Wild Species of Gentians (Gentiana spp.)

“…Our results have been consistent with those reported by Doi et al (2011), who examined the gynogenetic responses of six developmental stages of flowers and found that the later stages (just before anthesis or flower anthesis) were more responsive than bud stages in cultivated gentians. These results for gentians are also observed for other crops, of which the explants from just before anthesis or at anthesis (embryo sac is mature) show the highest gynogenic response (Chen et al 2011, Dong et al 2016, Khan et al 2020, Mukhambetzhanov 1997).…”

Haploid Induction in Tomato (Solanum lycopersicum L.) via Gynogenesis

“…In the case of self-pollinated species, in vitro culture of unfertilized female gametes is achieved by culturing flower buds prior to anthesis, while in male-sterile or selfincompatible plants it is performed at any stage of ovule development, since they show a favorable response to gynogenic induction [24]. This technique is successfully employed in species of the genus Allium, where it is the main technique to derive DHs [44]. For example, Panahandeh et al [45] achieved a gynogenic induction range of 5 to 12% by culturing unpollinated flower buds of Allium hirtifolium Boiss., which allowed callus formation with a success rate of 20%, of which the efficiency of obtaining haploid plants was 70 to 77%.…”

The Inheritable Characteristics of Monoecy and Parthenogenesis Provide A Means for Establishing A Doubled Haploid Population in the Economically Important Brown Alga Undariapinnatifida (Laminariales, Alariaceae)

“…Establishment of DH lines has accelerated the breeding progress and enhanced the breeding efficiency in many species of land crops (Weber 2014, Ferrie and Caswell 2016, Khan et al. 2020). They can either be used directly for selection of elite lines or serve as the parents of crosses for selection of superior hybrid lines.…”