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Ubon Ratchathani, Thailand

Fischer K.S.,University of Queensland | Fukai S.,University of Queensland | Kumar A.,International Rice Research Institute | Leung H.,International Rice Research Institute | Jongdee B.,Ubon Rice Research Center
Frontiers in Physiology

This paper is a section of the book "Drought phenotyping in crops: from theory to practice" (Monneveux Philippe and Ribaut Jean-Marcel eds, published by CGIAR Generation Challenge Programme. Texcoco, Mexico). The section describes recent experience in drought phenotyping in rice which is one of the most drought-susceptible crops. The section contains genetic and genomic resources for drought adaptation and methods for selection of drought-resistant varieties in rice. In appendix, there is experience from Thailand on integration of direct selection for grain yield and physiological traits to confer drought resistance. © 2012 Fischer, Fukai, Kumar, Leung and Jongdee. Source

Iseki K.,Kyoto University | Homma K.,Kyoto University | Shiraiwa T.,Kyoto University | Jongdee B.,Ubon Rice Research Center | Mekwatanakarn P.,Ubon Rice Research Center
Field Crops Research

Oxidative damage occurring in plant cells under drought stress is a known cause of reduced plant primary production. Decreasing oxidative damage through oxidative stress tolerance is expected to confer drought stress tolerance. In this study, we estimated cross-tolerance to oxidative stress and drought stress for breeding populations and analyzed the effects of the cross-tolerance on dry matter production in field experiments. For a total of 91 rice genotypes, including 72 backcross lines (BCLs), cross-tolerance was estimated from the first principal component score (PCS1) derived from a principal component analysis using a data set with a parameter of chlorophyll fluorescence and cell membrane stability index in both the oxidative and the drought stress treatments as the factors. The higher cross-tolerance was represented by the higher PCS1, and generally the values of PCS1 were segregated in the BCLs, suggesting that cross-tolerance is a heritable trait that can be improved by crossbreeding. The effects of positive and negative PCS1 on dry matter production under flooded and aerobic conditions were tested in field experiments. The decrease in dry matter production under aerobic conditions was smaller for the positive PCS1 genotypes. However, these genotypes also showed a lower stomatal conductance and smaller shoot biomass, especially under flooded conditions. We concluded that cross-tolerance is a useful trait for improving dry matter production, especially under severe drought stress. In view of the trade-offs between cross-tolerance and dry matter production, it is important to develop rice varieties with an optimal level of cross-tolerance for a target environment characterized by drought stress. © 2014 Elsevier B.V. Source

Iseki K.,Kyoto University | Homma K.,Kyoto University | Shiraiwa T.,Kyoto University | Jongdee B.,Ubon Rice Research Center | Mekwatanakarn P.,Ubon Rice Research Center
Field Crops Research

Mild intermittent drought is one of the major factors of yield reduction in rainfed rice. To minimize the yield reduction, the mechanisms that maintain photosynthetic activity play a crucial role for sufficient plant growth. The photoinhibition of photosystem II (PSII) depends on the balance between the rate of energy absorption and the rate of energy dissipation, including the energy flux for photosynthesis. Photoinhibition decreases the photosynthetic rate and restricts the primary production of the plant. In contrast, PSII photoinhibition can be regarded as a redox control mechanism that alleviates the excess light energy. In this study, the genotypic variation of photoinhibition in rice was examined in relation to the adaptability of photosynthesis to the fluctuating soil water conditions. 20 rice genotypes were grown under flooded and aerobic conditions, and the midday photoinhibition was evaluated by measuring the maximum quantum yield of PSII (Fv/Fm, a parameter of chlorophyll fluorescence). The larger decrease in Fv/Fm under aerobic condition than flooded condition was thought to be caused by the photosynthetic depletion derived from stomatal closure. The decrease of Fv/Fm occurred concomitantly with the increase of non-photochemical quenching (NPQ). Enhanced photoinhibition and NPQ might oxidize the redox state of the plastoquinone (PQ) pool under the aerobic condition to the same level as that under the flooded condition. The genotypic variation of the Fv/Fm and energy partitioning were affected little by the mild soil water deficiency of the aerobic condition. The genotypic variation of the midday Fv/Fm was dependent on the decreasing rate of Fv/Fm against an increase in midday light intensity. Some genotypes that showed more severe midday photoinhibition tended to have a lower rate of reduction of the shoot dry weight under the aerobic condition. These findings suggest that photoinhibition is a preferable trait for energy control in PSII and for photosynthesis under mild soil water deficiency. © 2012 Elsevier B.V. Source

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