First, second, and fifth authors: National Agricultural Research Center for Tohoku Region, Iwate 020-0198, Japan; third author: National Agricultural Research Center for Kyushu Okinawa Region, Kumamoto 861-1192, Japan; fourth author: College of Agriculture and Life Science, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju 500-757, South Korea; and sixth author: The University of Tokyo, Tokyo 116-8657, Japan
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Accepted for publication 5 December 2005.
The effect of elevated atmospheric CO2 concentration on rice blast and sheath blight disease severity was studied in the field in northern Japan for 3 years. With free-air CO2 enrichment (FACE), rice plants were grown in ambient and elevated (≈200 to 280 μmol mol-1 above ambient) CO2 concentrations, and were artificially inoculated with consist of Magnaporthe oryzae. Rice plants grown in an elevated CO2 concentration were more susceptible to leaf blast than those in ambient CO2 as indicated by the increased number of leaf blast lesions. Plants grown under elevated CO2 concentration had lower leaf silicon content, which may have contributed to the increased susceptibility to leaf blast under elevated CO2 concentrations. In contrast to leaf blast, panicle blast severity was unchanged by the CO2 enrichment under artificial inoculation, whereas it was slightly but significantly higher under elevated CO2 concentrations in a spontaneous rice blast epidemic. For naturally occurring epidemics of the sheath blight development in rice plants, the percentage of diseased plants was higher under elevated as opposed to ambient CO2 concentrations. However, the average height of lesions above the soil surface was similar between the treatments. One hypothesis is that the higher number of tillers observed under elevated CO2 concentrations may have increased the chance for fungal sclerotia to adhere to the leaf sheath at the water surface. Consequently, the potential risks for infection of leaf blast and epidemics of sheath blight would increase in rice grown under elevated CO2 concentration.
© 2006 The American Phytopathological Society