Evaluating the resistance of six rice cultivars to drought: restriction of deep rooting and the use of raised beds |
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Authors: | Yoichiro Kato Akihiko Kamoshita Junko Yamagishi |
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Institution: | (1) Field Production Science Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Midori-cho 1-1-1, Nishitokyo, Tokyo 188-0002, Japan;(2) Asian Natural Environmental Science Center, The University of Tokyo, Midori-cho 1-1-1, Nishitokyo, Tokyo 188-0002, Japan |
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Abstract: | Soil water deficits reduce rice (Oryza sativa L.) productivity under upland field conditions. In this study, we constructed screening facilities to evaluate the performance
of rice cultivars under drought conditions and to assess the roles of deep roots. Two experiments were conducted with six
rice cultivars, including drought-tolerant and drought-susceptible cultivars, grown in two root environments: a root-restricted
treatment that restricted rooting depth with water-permeable sheets, and a raised bed that reduced water availability in the
surface soil by inserting a gravel layer between the topsoil and subsoil layers to interrupt capillary transport of water.
In the root-restricted treatment, in which root growth was restricted to the surface 25-cm layer, leaf water potential decreased
faster in cultivars with a large canopy during drought stress, and there was little difference in panicle weight among cultivars.
With a normal (unrestricted) root environment, the deepest-rooting cultivar (‘IRAT109’) maintained higher leaf water potential
during drought, although panicle weight under drought stress was affected by yield potential as well as by deep rooting. Under
the intermittent drought stress in the raised bed, deep-rooting cultivars accumulated more nitrogen and produced more biomass,
and the difference in panicle weight between deep-rooting drought-tolerant and shallow-rooting drought-susceptible cultivars
was magnified by the raised bed compared with the yield differences under drought in a normal root environment. These results
demonstrate that the drought screening facilities we developed can help to identify superior cultivars under upland field
conditions without time-consuming measurement of deep root systems. |
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Keywords: | Aerobic rice Deep roots Drought screening Genotypic variation Upland rice Water-saving agriculture |
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