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Pak. J. Bot., 42(5): 3387-3398, 2010.

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Water deficit stress in the reproductive stage of four indica rice (Oryza sativa L.) genotypes

Suriyan Cha-um¹*, Suravoot Yooyongwech² and Kanyaratt Supaibulwatana³

Abstract: Relative water content (RWC) in the leaf of different rice cultivars dropped significantly in relation to reduced soil water content (SWC), especially in PT1 and IR20. In contrast, the proline content in the leaf-blade and leaf-sheath increased when plants were subjected to 7% SWC. The RWC was positively related to chlorophyll degradation. Chlorophyll a, chlorophyll b, total chlorophyll, total carotenoids, maximum quantum yield of PSII, stomatal conductance and water use efficiency in rice grown under water-deficit conditions declined significantly in comparison to the control group, leading to a reduction in net-photosynthetic rate. In addition, when exposed to water-deficit, panicle length and fertile grains in KDML105 and NSG19 were stabilized, leading to greater productivity than in PT1 and IR20. These data were utilized as effective criteria for the classification of water-deficit tolerance. From the results, KDML105 and NSG19 were identified as water deficit-tolerant, and PT1 and IR20 as water deficit-susceptible.

¹National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand

²Department of Agricultural Science, Faculty of Science and Technology, Mahidol University (Kanchanaburi campus), Kanchanaburi 71150, Thailand

³Department of Biotechnology, Faculty of Science, Mahidol University, Payathai, Bangkok 10400, Thailand