Avid readers of the Botany One blog will no doubt be aware of The Story of Soy. Written by Christine du Bois it makes the compelling case for the global importance of that crop plant. But, as productive and globally important as soy (Glycine max) is, it can always be improved. And that’s what Abraham Akpertey et al. have achieved.
Whenever crop improvement is mentioned these days one might be forgiven for assuming it must be down to genetic engineering or gene-editing. However, in this instance it’s good old-fashioned, ‘traditional’ pant breeding that we have to thank. Even then it wasn’t straightforward. The team made crosses between G. max (commercial soya), which has a chromosome complement of 2n = 40, and a wild relative, Glycine tomentella (rusty glycine) (2n = 78). As you might imagine, the offspring of this union had a strange number of chromosomes – ‘2n = 59’, and was sterile – which is not a lot of use for developing a new generation of higher yielding plants.
However, with use of colchicine, a plant-derived ‘chromosome-doubling’ compound, a fertile ‘amphidiploid’ with 2n = 118 was created. Using this plant and lots of ‘back-crossing‘ to soya, Akpertey et al. were able to create new soya plants with 2n = 40, which were self-fertile and genetically stable. Containing approx. 1% of G. tomentella genetic heritage, these G. max offspring were considerably higher-yielding than the existing ‘genetically pure’ G. max. So, soy, not so max after all?* Unless, it gets help from a relative!
This story is an important reminder that so-called ‘conventional’ or ‘traditional’ plant breeding can still contribute to improving crop plants, and is an additional methodology to genetic engineering and gene-editing.** It also demonstrates the potential to consider wild relatives of our crop species – so-called crop wild relatives (CWRs) – as sources of useful genetic characteristics as we seek all – and any – methods of crop improvement to provide future food security.*** Another boost to more targeted soya improvement is likely to come from the publication of the genome of soy cultivar Zhonghuang 13, which has capacity for high yield and high stress tolerance.****
* Maybe it should be re-named Glycine sub-maxima..?
** Although use of colchicine to manipulate chromosome number must surely be considered a sort of genetic modification because it modifies the number of chromosomes that contain the genes…
*** This story also demonstrates the part played by serendipity in scientific discovery. Apparently, the original investigation concerned the desire to breed resistance against soybean rust into G. max from G. tomentella, which they achieved. The yield increase was a rather nice – and most welcome – bonus (and one that’s presumably not related to the disease-resistance…).
**** Somewhat bizarrely, extracts of Glycine tomentella have proved effective as a “stress-tolerance enhancing agent in the aquaculture industry”]…
Akpertey, A., Singh, R. J., Diers, B. W., Graef, G. L., Mian, M. A. R., Shannon, J. G., … Nelson, R. L. (2018). Genetic Introgression from to Soybean to Increase Seed Yield. Crop Science, 58(3), 1277. https://doi.org/10.2135/cropsci2017.07.0445
Hajjar, R., & Hodgkin, T. (2007). The use of wild relatives in crop improvement: a survey of developments over the last 20 years. Euphytica, 156(1-2), 1–13. https://doi.org/10.1007/s10681-007-9363-0
Dempewolf, H., Baute, G., Anderson, J., Kilian, B., Smith, C., & Guarino, L. (2017). Past and Future Use of Wild Relatives in Crop Breeding. Crop Science, 57(3), 1070. https://doi.org/10.2135/cropsci2016.10.0885
Shen, Y., Liu, J., Geng, H., Zhang, J., Liu, Y., Zhang, H., … Tian, Z. (2018). De novo assembly of a Chinese soybean genome. Science China Life Sciences, 61(8), 871–884. https://doi.org/10.1007/s11427-018-9360-0
Chuang, W.-L., & Sun Pan, B. (2011). Anti-Stress Effects ofGlycine tomentellaHayata in Tilapia: Inhibiting COX-2 Expression and Enhancing EPA Synthesis in Erythrocyte Membrane and Fish Growth. Journal of Agricultural and Food Chemistry, 59(17), 9532–9541. https://doi.org/10.1021/jf2017308