Variation in carbon isotope discrimination and its relation to yield of irrigated rice
1998
Laza, M.R.C. | Shaobing Peng (International Rice Research Inst., P.O. Box 933, 1099 Manila (Philippines))
Carbon isotope discrimination [Cid], a measure of the molar ratio of 13 C to 12 C, is a highly heritable character with considerable genotypic variation. It has been reported in wheat that carbon isotope discrimination was correlated with yield. Thus, it could be a useful tool for selecting genotypes with improved yield potential. A study was conducted to determine the variation in Cid among rice genotypes grown in diverse environments. Field experiments were conducted between 1992 and 1995 wet and dry seasons in different sites at IRRI, PhilRice and Yunnan Province in China. Rice genotypes were grown under irrigated conditions at different nitrogen levels ranging from 0-295 kg N/ha. Grains were collected at physiological maturity and flag leaves were sampled at flowering. Isotopic composition was analyzed by mass spectrophotometrically at the Research School of Biological Sciences, Australian National University, Canberra, Australia. Grain yield expressed at 14 percent moisture content was determined from a 5 sq m plot. Within each experiment, Cid was similar among genotypes although their grain yields were significantly different in some cases. Variation in Cid across locations and years existed, but this variation was not associated with yield. Fertilizer nitrogen (N) had no effect on Cid, although there were large differences on grain yield across N treatments. These results suggest that in rice, Cid is not a good criterion for selecting genotypes with high yield potential
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