Rice Production in China
Peng, S., Tang, Q. and Zou, Y. 2009. Current status and challenges of rice production in China. Plant Production Science 12: 3-8.
Further complicating the picture are several unfavorable trends, among which Peng et al. include a decline in arable land, increasing water scarcity and climate change, to which they add the problems of "overuse of fertilizers and pesticides, breakdown of irrigation infrastructure, oversimplified crop management, and a weak extension system."
So what might be done to rectify the situation and prevent what would appear to be a massive disaster-in-waiting? The three researchers highlight five plant characteristics they feel could be improved by innovative breeding techniques: yield potential, drought tolerance, heat tolerance, disease resistance, and insect resistance. However, they fail to discuss them within the context of the ongoing rise in the air's CO2 content, which is a most important oversight.
Consider, for example, the case of yield potential. Working at the National Institute for Agro-Environmental Sciences in Tsukuba, Japan, Lou et al. (2008) grew four different rice cultivars within growth chambers maintained at atmospheric CO2 concentrations of 370 and 570 ppm, finding that the extra 200 ppm of CO2 actually reduced the ultimate grain yield of one of the varieties (but by only 0.7%), while it increased the final grain yield of the other three varieties by 8.0%, 13.4% and 17.7%. Likewise, working at the FACE facility at Yangzhou City, Jiangsu Province, China, Yang et al. (2009) studied a single two-line inter-subspecific hybrid rice variety that was produced as part of a mega project to develop "super" hybrid cultivars that would "further break the yield ceiling." And in their three-year study, which employed the same CO2 levels as that of Lou et al., they found a much greater CO2-induced grain yield stimulation: 28.4% at low nitrogen fertility and 31.7% at high nitrogen fertility. Hence, they concluded "there is a pressing need to identify genotypes which could optimize harvestable yield as atmospheric CO2 increases." The same situation exists with respect to drought and heat tolerance, and with respect to disease and insect resistance. Atmospheric CO2 enrichment generally tends to enhance all four of these important plant functions.
Just as there are species and variety differences in crop yield response to elevated CO2 concentrations, so are there species and varietal differences in the responses of crop drought and heat tolerance and crop disease and insect resistance to elevated levels of CO2. Therefore, breeding for optimum performance of these important plant functions in a high-CO2 world of the future should also be a prime objective in meeting the challenge of adequately feeding the planet's future population. And the fact that the need for this "do or die" effort is not all that far distant, only makes the work required to achieve it all that more urgent. Are we up to the task?
Lou, Y., Inubushi, K., Mizuno, T., Hasegawa, T., Lin, Y., Sakai, H., Cheng, W. and Kobayashi, K. 2008. CH4 emission with differences in atmospheric CO2 enrichment and rice cultivars in a Japanese paddy soil. Global Change Biology 14: 2678-2687.
Yang, L., Liu, H., Wang, Y., Zhu, J., Huang, J., Liu, G., Dong, G. and Wang, Y. 2009. Yield formation of CO2-enriched inter-subspecific hybrid rice cultivar Liangyoupeijiu under fully open-air condition in a warm sub-tropical climate. Agriculture, Ecosystems and Environment 129: 193-200.