Paper Reviewed
Mitterbauer, E., Enders, M., Bender, J., Erbs, M., Habekuß, A., Kilian, B., Ordon, F. and Weigel, H.-J. 2017. Growth response of 98 barley (Hordeum vulgare L.) genotypes to elevated CO2 and identification of related quantitative trait loci using genome-wide association studies. Plant Breeding 136: 483-497.

Feeding the growing population of the planet that is projected to reach nine billion persons just three decades from now has become a growing concern among scientists and policy makers. The latest group to investigate this important topic is the eight-member research team of Mitterbauer et al. (2017).

Writing as background for their work, Mitterbauer et al. say that "as rising CO2 represents a major resource for plant growth, targeted exploitation of this resource by plant breeding to optimize yields can be considered as an option to contribute to future food security," citing the works of Aspinwall et al. (2015) and Ziska et al. (2012). Yet to accomplish this objective, scientists must first identify which genotypes of a given plant species are most responsive to atmospheric CO2 enrichment. Thereafter, genetic markers can be identified as "a tool for breeders to select for biomass enhancement under future CO2 conditions ... as a vital component to breed for better crop yields in [the] future."

Against this backdrop, Mitterbauer et al. set out to examine the responsiveness of 98 barley (Hordeum vulgare) genotypes to elevated CO2. Barley was selected because it is an important global food crop, with a production total of 144.3 million tons in 2014. The plants were grown over a two year period in open-top chambers at an experimental field station in Braunschweig, Germany. Elevated CO2 was provided during daylight hours to a target concentration of 700 ppm (300 ppm above ambient). Soil water content was kept above 60% field capacity and applications of fertilizer, herbicides and pesticides were applied in accordance to local farming practices.

In discussing their findings, Mitterbauer et al. note that, when averaged across all genotypes, there was no difference in developmental time span in reaching the various stages of growth under ambient or elevated CO2 conditions. However, elevated CO2 stimulated the aboveground biomass of the barley plants by 15 percent when averaged across all years and genotypes. Of greater importance is the fact that a number of genotypes experienced aboveground biomass enhancements of over 50 percent in response to elevated CO2, with the two highest responses reaching nearly 100 percent!

Clearly, much more research needs to be done to identify which genotypes of the important food crops produce the greatest yield responses per incremental rise in atmospheric CO2. Thereafter, scientists can identify the mechanisms responsible for such responses, breeders can exploit them, and farmers can grow the best varieties to produce the highest possible yields. It is a beautiful blueprint to ensure future global food security.

References
Aspinwall, M.J., Loik, M.E., Resco De Dios, V., Tjoelker, M.G., Payton, P.R. and Tissue, D.T. 2015. Utilizing intraspecific variation in phentotypic plasticity to bolster agricultural and forest productivity under climate change. Plant Cell & Environment 38: 1752-1764.

Ziska, L.H., Bunce, J.A., Shimono, H., Gealy, D.R., Baker, J.T., Newton, P.C.D., Reynolds, M.P., Jagadish, K.S.V., Zhu, C., Howden, M. and Wilson, L.T. 2012. Food security and climate change: On the potential to adapt global crop production by active selection to rising atmospheric carbon dioxide. Proceedings of the Royal Society B: Biological Sciences 279: 4097-4105.