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Xangsayasane P.,National Agriculture and Forestry Research Institute | Xangsayasane P.,Khon Kaen University | Jongdee B.,Bureau of Rice Research and Development BRRD | Pantuwan G.,Bureau of Rice Research and Development BRRD | And 4 more authors.
Field Crops Research | Year: 2014

Drought is a major constraint to rice production in the rainfed lowlands of South East Asia. The timing and severity of water stress is highly variable from year to year and the current drought screening method for rainfed lowland rice utilizes a late planting to impose a prolonged terminal drought in the wet season. In this paper, an alternative drought screening method was investigated for areas where photoperiod insensitive genotypes are commonly grown with the aim of identifying promising genotypes exposed to short-duration intermittent drought, a condition that is more frequently experienced in the rainfed lowlands in the wet season. To assess the usefulness of intermittent drought screening the performance of genotypes was compared with that tested under traditional flooded and terminal drought treatments in wet and dry seasons for two years. Mean yield reduction in intermittent and terminal drought was 13 and 35% respectively in the wet season and 34 and 59% respectively in the dry season, indicating that the proposed intermittent drought screening in the dry season and the current terminal drought screening in wet season would provide the magnitude of drought severity that would be appropriate for screening. Genotypes shown to be drought tolerant, based on their drought response index (DRI), were consistent in intermittent and terminal drought screening. There was no significant relationship between potential grain yield obtained under well watered treatments and DRI, indicating that some drought tolerant genotypes can achieve high yield, thus adaptation to a wide range of rainfed lowland conditions is expected. Due to genotypic variation in flowering in relation to rainfall or irrigation events in the terminal and intermittent drought treatments respectively, delay in flowering was not consistent across experiments and thus, is not expected to be a useful trait for selection particularly when using intermittent screening methods. It is therefore concluded that intermittent drought with appropriate level of drought stress could be used with DRI as a criterion for selection of well adapted genotypes suitable for the rainfed lowlands. © 2013 Elsevier B.V.


Monkham T.,Khon Kaen University | Jongdee B.,Khon Kaen University | Pantuwan G.,Bureau of Rice Research and Development BRRD | Sanitchon J.,Khon Kaen University | And 2 more authors.
Field Crops Research | Year: 2015

Rainfed lowland rice in the Mekong region is mostly grown in drought-prone areas, and drought resistant varieties could be selected using either terminal drought (severe water stress after flowering) or intermittent drought (frequent mild stress) screening. Delay in flowering is considered as a putative trait for selection of drought resistant genotypes, and its effectiveness as an indirect selection trait and its association with genotype's flowering duration, i.e. the time taken from the first to last flower in a plot, was evaluated under the two drought screening methods. These screening methods together with flood control were used at two locations, Chum Phae and Ubon in north-east Thailand using a total of 70 genotypes with different growing duration. Delay in flowering was estimated for the two drought screening methods and flowering of individual panicles within a plot was recorded to determine flowering duration of each genotype in the flood and terminal drought conditions.Mean reduction in grain yield was 52-55% under the terminal drought screening while it was 10-19% for the whole population and 23-33% for early flowering genotypes in the intermittent drought. Delay in flowering under intermittent drought condition at both locations was associated with yield reduction; genotypes that exhibited shorter delay in flowering had smaller yield reduction percentage and larger number of panicles. At Chum Phae, where grain yield reduction was associated with flowering time, genotypes with longer flowering duration under terminal drought had smaller yield reduction, and this was found even among genotypes that flowered about the same time under flood condition. However, there was no association between delay in flowering and flowering duration. It is concluded that delay in flowering appears promising as a selection criterion under intermittent drought conditions, provided a higher yield reduction can be achieved for example by using an increased irrigation interval. © 2015 Elsevier B.V.

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