• Question: Can somatic hybridation by men be possible? And is there a difference with hybridation made with sexual reproduction process concerning the "improvement" of the hybrid plant.

    Asked by ines et noemie to Zarah, Kon, Kirsten, Jena, Freddie on 16 Nov 2016.
    • Photo: Jennifer Bates

      Jennifer Bates answered on 16 Nov 2016:

      Cool question, thanks. 🙂

      So, the genetic modification of two distinct plant species to make a new hybrid plant (somatic hybridisation) with characteristics from both original species has been carried out by humans. Triticale, a hybrid of wheat and rye, was first made in the 19th century with the aim of getting the high yields from wheat and environmental tolerances of rye. However, there are often problems of low fertility, so the second generation of Triticale (Triticale crossed with another Triticale) is the one that people buy and grow.

      There are key differences between somatic hybridisation and sexual reproduction. Sexual reproduction obviously requires members of same species or closely related wild species. Somatic hybridisation can allow for the creation of novel plants that overcome the species boundaries, with the aim of reducing the weaknesses inherent to the original species, as identified by humans (e.g.: the environmental intolerances of wheat and the low yields of rye). Even if, as humans, we are trying to create a new hybrid from something of two related species that are close enough to reproduce sexually, somatic hybridisation allows material from both parents to be included, while sexual reproduction favours the maternal parent.
      Other benefits of somatic hybridisation could include the targeting of specific traits, such as abiotic stress through the fusion of protoplasts of plant bearing a particular character to the other plant which may be susceptible to diseases, because these traits are often cytoplasmically encoded and can be easily transferred, and the creation of plants from sexually sterile plants (haploid, triploid, aneuploid plants) by fusing them to fertile plants (diploids and polyploids). The plant can also be in its juvenile stage for somatic hybridisation, so less time and effort in growing is involved at this point.

      However, there are limits, as with all things!
      It’s obviously not easy or straight forwards to do! And once you have a hybrid they can often be infertile, or face unforeseen problems, and worse, the trait you wanted might not even express itself (all that effort for nothing!). A new form, called an amphidiploid, can be made from two diploids, which is not great. It’s all extremely difficult to introduce wild species genetic material to cultivated crops (not impossible, but difficult).

      So, as with all things in science the questions you have to ask are: why are we doing this and what do we want to achieve?

      With Triticale, I think it was probably a good thing, in the long run. It has a higher protein content than wheat but it does have a lower glutenin content (the thing that makes bread dough stretchy) so we’d need to change the way we make flour and bread slightly. On the plus side again, it is higher in lysine, which is essential for humans and we have to get it from out diet, we can make it in our bodies. And the starch content is easy to digest so it makes a great animal feed, and is already widely used as one.

      With other crops though it will need to be thought about on a crop-to-crop basis. It might sound cool to mix a tomato with tobacco (as in the Simpsons), but there are all kinds of questions as to why you might want to do this, and what problems we might face down the line in terms of plant sterility or unforeseen consequences.

      In the meantime, maybe check out this project on rice and photosynthesis: https://c4rice.com/ They are trying to improve the photosynthesis in rice plants by changing it to a C4 pathway (from C3) and thus increase the grain yield. Pretty amazing.