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Root growth response of rainfed lowland rice to aerobic conditions in northeastern Thailand

Kato, Yoichiro, Tajima, Ryosuke, Homma, Koki, Toriumi, Akiko, Yamagishi, Junko, Shiraiwa, Tatsuhiko, Mekwatanakarn, Poonsak, Jongdee, Boonrat
Plant and soil 2013 v.368 no.1-2 pp. 557-567
aerobic conditions, branching, lowlands, paddies, rice, root growth, rooting, roots, soil water, topsoil, water stress, Thailand
Background and aims: Rice plants alternately experience anaerobic and aerobic conditions during their life cycle in rainfed lowlands. Each condition affects root growth differently. Our objective was to clarify the specific rice root response to aerobic conditions in rainfed lowlands. Methods: At the Ubon Ratchathani Rice Research Center in northeastern Thailand, we obtained root samples from 17 'Surin1' (Thai variety) BC3-derived lines and 7 CT9993-5-10-1-M × IR62266-42-6-2 doubled-haploid lines from flooded and non-flooded paddy fields at the reproductive stage in 2010 and 2011. Results: In the non-flooded trial, rice was grown aerobically by draining the perched water; soil moisture at a depth of 20 cm fluctuated between -10 and -30 kPa. Deep rooting was likely promoted under aerobic conditions, but slightly drier soils under longer dry spells seemed to restrict root penetration, as the topsoil rapidly hardened during dry spells of only a few days. Fine-root development in the topsoil was inhibited under aerobic conditions. Conclusions: Even without drought stress, rice roots respond significantly to the disappearance of standing water in rainfed lowlands via deep rooting and root branching. We identified one promising 'Surin1' BC3-derived line showing an adaptive response of deep rooting under aerobic conditions, which can be used as a breeding material for rainfed lowland rice in Thailand. © 2012 Springer Science+Business Media Dordrecht.