23 Oct 2020

What is Gynogenesis?

Anjali Singh, MS

As a content and community manager, I leverage my expertise in plant biotechnology, passion for tissue culture, and writing skills to create compelling articles, simplifying intricate scientific concepts, and address your inquiries. As a dedicated science communicator, I strive to spark curiosity and foster a love for science in my audience.

Table of Contents

Basics: Gynogenesis

The development of entire plants from unfertilized female gametes is termed, "gynogenesis." It serves as a valuable alternative to haploid production for species in which anther culture (Androgenesis) fails to give satisfactory results. It was first reported by a scientist named San Noeum in 1976 and, so far, it’s been studied in 19 species belonging to 10 different families.

In nature, gynogenesis occurs through parthenogenesis, and in labs, the embryo formation by female gametophyte occurs via two pathways: direct embryogenesis (formation of an embryo without callus) and indirect embryogenesis (formation of an embryo with intermediary callus formation).

In this article, you will get an understanding of the history and the factors affecting gynogenesis.

History of Gynogenesis

The research on haploid production by gynogenesis was initiated in 1965. However, the research didn’t get much attention because of the breakthrough made by Guha and Maheshwari (1964) in the production of androgenic haploids.

In 1971, significant research on gynogenesis was initiated. A report published by Uchimiya et al. showed the division of haploid cells forming callus when unpollinated ovaries of Zea mays and ovules of Solanum melongena were cultured.

Successful reports on gynogenic haploids were first published in 1976 and 1979 by San Noeum and it has now been studied in several economically important plants. These include wheat, rice, barley, maize, sunflower, etc.

The production of a haploid by gynogenesis is influenced by several key factors that are discussed in the section below.

Factors Affecting Gynogenesis

1. Explants (the part of the plant to start from)

Young flowers, ovary, ovule, and unfertilized parts of the embryo sac are considered suitable explants, depending on species and the application thereof. For example, only ovule culture has been successfully observed in Gerbera jamesonii. In rice and barley, culturing whole florets gives better results.

The stage of explant tissue required also differs significantly from case to case. When anthers are not mutated, the young flowers are used in most cases--except in the case of male-sterile plants.

2. Pre-treatments of the explant

Cold treatment, starvation, and heat shock of explants have been very useful in enhancing haploid production by gynogenesis. For example, treating sunflowers at 4℃ for 24-48 hours before culturing results in an increase of the overall embryo yield.

In rice, sugar beet, wheat, and Salvia sclarea, cold treatment at 8℃ for 14-16 days enhances the gynogenic response to multifold. In some species, like Picea sitchensis and cucumber spp., heat shock treatment (during the culture/induction phase) at 32-33℃ has been observed to promote the sporophytic development of the female gametophyte. However, in many other species like niger, Cucurbita pepo, and rice spp., any pretreatment causes detrimental effects.

3. Culture Medium

N6 and MS media with a high concentration of sucrose (different concentrations depending on the species) are the most suitable media to produce maternal haploids. In gramineous species, the production of haploid can be induced in a media containing hormone or growth regulators (like 2,4-D, NAA, and BAP). However, in some species like sunflower, the presence of hormones suppresses the embryo development from a female gametophyte.

It should also be noted that the process of gynogenesis is a multistep process. So, each step has different requirements for nutrients, light exposure, and hormone regulators.

4. Genotype

The haploid production also depends on the donor plants and the response varies from species to species. For example, in Allium cepa, the open-pollinated cultivars show low response to gynogenesis than inbred lines and F 1 hybrids.

In some species of plants (like sugar beet), the florets grown on the lateral branches have better embryogenic response compared to the florets grown on the main branch.

Application of Haploid Production by Gynogenesis

Very few species have had their gynogenic response studied because it's less efficient, more tedious, and restricted in comparison to haploid production by androgenesis. However, this method has been observed as one of the best alternatives to haploid production in cases where androgenesis cannot be performed. Some examples are explained below.

1. Gynogenesis has been useful for haploid production in plants like sugar beet, onion, and melon.
2. It’s been an essential technique for haploid production in male-sterile plants. Some successful cases have been observed in unfertilized ovary culture.
3. The technique has been used to produce green haploids where albinism was a problem. For example, in rice, 83% of green plants were observed in gynogenic cultures compared to 1% in androgenic plants.
4. In some species of plants (like rice), it has been found that gynogenic cultures are more efficient and yield more haploids than androgenic cultures.

References

1. Haploid production. (1996). Studies in Plant Science, 167–213. DOI:10.1016/s0928-3420(96)80009-7
2. Asif, M. (2013). Gynogenesis: An Important Tool for Plant Breeders. SpringerBriefs in Plant Science, 45–51. DOI:10.1007/978-3-319-00732-8_3
3. Sita, G. L. (1997). Gynogenic haploids in vitro. Current Plant Science and Biotechnology in Agriculture, 175–193. DOI:10.1007/978-94-017-1856-1_10