Protoplast Technology and Somatic Hybridisation in the Family Apiaceae

Abstract

Species of the family Apiaceae occupy a major market share but are hitherto dependent on open pollinated cultivars. This results in a lack of production uniformity and reduced quality that has fostered hybrid seed production. The difficulty in flower emasculation led breeders to use biotechnology approaches including somatic hybridization. We discuss the use of protoplast technology for the development of somatic hybrids, cybrids and in-vitro breeding of commercial traits such as CMS (cytoplasmic male sterility), GMS (genetic male sterility) and EGMS (environment-sensitive genic male sterility). The molecular mechanism(s) underlying CMS and its candidate genes are also discussed. Cybridization strategies based on enucleation (Gamma rays, X-rays and UV rays) and metabolically arresting protoplasts with chemicals such as iodoacetamide or iodoacetate are reviewed. Differential fluorescence staining of fused protoplast as routinely used can be replaced by new tagging approaches using non-toxic proteins. Here, we focused on the initial plant materials and tissue sources for protoplast isolation, the various digestion enzyme mixtures tested, and on the understanding of cell wall re-generation, all of which intervene in somatic hybrids regeneration. Although there are no alternatives to somatic hybridization, various approaches also discussed are emerging, viz., robotic platforms, artificial intelligence, in recent breeding programs for trait identification and selection.

Keywords: biotechnological breeding; carrot; celery; cybrids; male sterility; protoplast isolation and fusion.

Figure 1

Yield data of primary crops of the year 2020 from Food and Agriculture Organization of the United Nations (https://www.fao.org/faostat/en/#data/QCL) (accessed on 10 February 2022).

Figure 2

(A) Simple genetic model of Genic male sterility (GMS), (B) Maintenance of parent line and hybrid seed production for GMS, (C) Simple genetic model of Cytoplasmic Male Sterility (CMS), (D) Maintenance of parent line and hybrid seed production for CMS.

Figure 3

Symmetric and asymmetric protoplast fusion. Donor mitochondria (Green), acceptor mitochondria (Red).