Abstract
Breeding rice with high water use efficiency (WUE) can ameliorate water shortage through water-saving irrigation. However, WUE is a complex quantitative trait and very few studies have been conducted to measure WUE directly. In this study, a recombined inbred line population derived from a cross between an indica lowland rice and upland japonica rice was used to dissect the genetic control of WUE by fine-monitored water supply experiments. Quantitative trait loci (QTL) were scanned for 10 traits including heading date (HD), water-consumption per day (water/d), shoot weight gain per day (shootw/d), root weight gain per day (rootw/d), kernel weight gain per day (kernelw/d), average WUE at whole plant level (WUEwhole/d), average WUE for up-ground biomass (WUEup/d), average WUE for grain yield (WUEyield/d), average economic index (econindex/d), and average root/shoot ratio per day (ratio/d). The results show that most of the traits were significantly correlated to each other. Twenty-four QTL (LOD ⩾ 2.0) were detected for econindex, econindex/d, WUEyield, WUEyield/d, WUEup, WUEup/d, WUEwhole, WUEwhole/d, kernelw, kernelw/d, rootw, and water/d by composite interval mapping. These QTLs are located on chromosomes 1, 2, 4, 6, 7, 8, and 12. Individual QTLs accounted for 4.97%–10.78% of the phenotypic variation explained. Some of these QTLs overlapped with previously reported drought resistance QTLs detected in this population. These results provide useful information for further dissection of the genetic basis and marker-assisted selection of WUE in rice.
Highlights
Breeding rice with high water use efficiency (WUE) can ameliorate water shortage through water-saving irrigation
The results show that strong correlations existed between all per-day traits and heading date (HD), suggesting that the per-day traits are suitable to evaluate WUE
To accurately monitor the water consumption, the water supply of each plant of the parents and recombined inbred line (RIL) were recorded daily and the pots were covered with thin plastic film to reduce variation in the evaporation of water from the soil surface
Summary
Breeding rice with high water use efficiency (WUE) can ameliorate water shortage through water-saving irrigation. Direct measurement of WUE at the plant level has the merits of directly recording water consumption over the whole growth cycle and relevant indicators such as biomass (even including roots if necessary) and yield, and it is considered the most accurate and trustworthy method for evaluating WUE of different varieties [7,8,10,19]. Yoichiro et al [13] conducted quantitative trait locus (QTL) mapping of WUE using 106 backcross inbred lines (BILs) derived from a cross between Akihikari (lowland rice) and IRAT109 (upland rice) at the seedling stage (30 d from germination) under non-stressed and PEG 6000-stressed conditions. Xu et al [8] detected seven QTLs for leaf WUE in a population of 98 BILs derived from a cross between temperate japonica and aus rice at the seedling stage (3–4 weeks from germination) with carbon isotope discrimination as the criterion. Mian et al [20] conducted QTL mapping on the WUE of beans with 120 F4 lines from the cross Young × PI416937 and detected four QTLs accounting for 38% of phenotypic variation
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