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Optimizing Crop Yield Responses to Atmospheric CO2 Enrichment
Volume 11, Number 42: 15 October 2008

In an important new paper authored by 32 researchers from 12 different countries (Ainsworth et al., 2008), the case is made for (1) breeding varieties of the major crops upon which the world depends for food to best take advantage of the ongoing rise in the air's CO2 content, which latter phenomenon is sure to continue for decades to come, and (2) employing Free-Air CO2-Enrichment or FACE technology to accomplish it.

The international consortium of scientists begins by reminding us that "the growing world population, increasing demands for grains for animal feeds, land loss to urban expansion and demand for bioenergy production are exerting more and more pressure on global agricultural productivity." Therefore, as they continue, "a major challenge for plant biologists, agronomists and breeders will be to provide germplasm and seed material that maximize future crop production," particularly within the context of rising atmospheric CO2 concentrations that provide, in their words, "a unique opportunity to increase the productivity of C3 crops." However, they report that "only a fraction of available germplasm of crops has been tested for CO2 responsiveness," and that "further research is needed to elucidate the mechanisms of yield response to CO2, to assess the genetic diversity available for improving responsiveness and to devise efficient schemes for selection for adaptation to rising ambient CO2, whether based on conventional plant breeding or systems biology approaches for selecting and engineering improved genetics."

The first step in meeting these objectives, according to the researchers, "is to create facilities for field screening the yield response to elevated CO2 across a wide range of germplasm," while doing it under "conditions and management that reflect dominant agronomic practices and provide as natural an environment as possible." Hence, they all agree that FACE experimentation is the way to proceed, since it meets these criteria and represents the least obtrusive interaction with the natural environment of any current or envisioned technology.

Although FACE systems are often considered expensive to construct and operate, Ainsworth et al. note that "the net cost is compensated for by economies of scale, and the cost per unit ground area is considerably less than alternative systems." This fact is very important, because, as they explain it, "the new research requires investigating large numbers of genotypes," the validity of which assessment is born out by their assertion that "to investigate the association of CO2 responsiveness with a single quantitative trait locus mapping population, approximately 150 inbred lines would need to be investigated."

In concluding their treatise, the world-renowned group of scientists states that "because it may take 10-15 years to move from discovery of new advantaged genetics to commercial cultivars of annual grain crops, developing a robust strategy and supporting the planned work with the best possible facilities should be an urgent priority." We could not agree more. This work must be done, and as rapidly as possible, if we are to prevent massive food shortages and the taking of unconscionable amounts of land and water from what we could call "wild nature" but a few short decades from now.

Sherwood, Keith and Craig Idso

Ainsworth, E.A., Beier, C., Calfapietra, C., Ceulemans, R., Durand-Tardif, M., Farquhar, G.D., Godbold, D.L., Hendrey, G.R., Hickler, T., Kaduk, J., Karnosky, D.F., Kimball, B.A., Korner, C., Koornneef, M., LaFarge, T., Leakey, A.D.B., Lewin, K.F., Long, S.P., Manderscheid, R., McNeil, D.L., Mies, T.A., Miglietta, F., Morgan, J.A., Nagy, J., Norby, R.J., Norton, R.M., Percy, K.E., Rogers, A., Soussana, J.-F., Stitt, M., Weigel, H.-J. and White, J.W. 2008. Next generation of elevated [CO2] experiments with crops: a critical investment for feeding the future world. Plant, Cell and Environment 31: 1317-1324.