| Maize (Zea mays1.) is the main food crops in the world,and is important forage and industrial raw materials.Drought is a major cause of yield loss in maize production all over the world, which is expected to increase with climatic changes predicted in the future as temperatures rise and rainfall distribution changes in many maize production areas. The alternative approach to solve this problem has been directed towards developing high yielding maize varieties under drought conditions.The objective of this study included three aspects.(1) In order to evaluate drought resistance criteria,10main maize varieties in Hunan and Southwest of China were tested under the irrigation and no irrigation regimes.(2) To understand the genetic causes underlying drought resistance and identify relevant quantitative trait locus (QTL), a F23mapping populations with160families derived from crosses of Lin1(drought resistance) and Xiang97-7(drought sensitive) were phenotyped under the well watered (WW) and water stressed (WS) treatments in two environments including Gaoqiao and Mapoling of Chang sha in2011. For the four target traits of anthesis to silking interval (ASI), plant height,1000kernel weight and grain yield were measured and the drought resistance coefficient (DRC) for each trait was considered as measurements for drought resistance.(3) Based on identification of drought resistance criteria, selection of drought inbred lines and hybrids are suitable for special ecological conditions in Hunan. The main results obtained in this paper were as follows:1. Drought had a significant influence on yield and main agronomic characters of maize. According to the correlation analysis of yield and its drought resistant coefficient,5parameters of yield, ASI, root depth, plant height and1000kernal weight were selected to be used as drought resistance criteria of maize. In this study,5parameters'average value of membership as comprehensive membership grade was used to evaluate the drought resistance of mazie varieties. The results indicated that the varieties with higher drought resistance is Fuyou9, Luoyul, Lin'aol, Keyu2, Nongdal08; the varieties with medium drought resistance is Yudan7, Lianhe3and the varieties with lower drought resistance is Dongdan57, Keyul, Dongdanl6. The results of comprehensive membership grade were consistent with many years of the drought resistance field performance of maize varieties.2. The phenotypic frequency of ASI, plant height,1000kernel weight and grain yield in F2:3mapping populations with160families revealed a quantitative variability and fitted a fairly normal distribution in both the well watered and water stressed treatments, which indicated these traits should be quantitative traits. ASI and grain yield was a significant negative correlation, but among plant height,1000kernel weight and grain yield were a significant positive correlation in both water regimes conditions.3. A linkage map was constructed based on110polymorphic simple sequence repeat (SSR), resulting in a length of1246.1cM across maize genome, with an average inter-marker distance of11.33cM, which resulted in coverage of85bin among the100bin across all maize genome. The arraying order and bin map of markers in the linkage map was in good agreement with IBM2008Neighbors Frame reference map.4. A total of43QTL were identified, with a minimum of8and a maximum of14for drought related traits. Phenotypic variation associated with each QTL ranges from6.27% to18.27%. Very few QTL were detected in two water treatments, indicating the different mechanisms may indeed coexist that together contribute to adaptation to drought stress. The QTL for drought related traits appeared to be dispersed across10different chromosomes, except chromosomes2and10. Most QTL for drought related traits in this study tended to cluster in some areas of the chromosome1and3, and mainly in bin1.02-03,1.06-07and3.04-05. Two QTL clusters on chromosome1flanked by the markers umc2224and bnlgl76for plant height,1000kernel weight and grain yield, and bnlgl556and umcl128for ASI and grain yield were identified. A cluster of QTL flanked by the markers umc1773and umc1311for plant height,1000kernel weight and grain yield were identified on chromosome3. These novel QTL clusters generated in this study may be used to enhance maize drought resistance by marker assisted selection (MAS) in water limited environments5. Xiangkangyu2was breeded, and was registered by Hunan Evaluation Committee of Crop Variety in2011(Xiangshenyu2011002). Xiangkangyu2is a high quality, high yield and drought resistant maize hybrids,The average yield and daily output were7851.8kg/hm2and71.25kg/hm2on regional test of Hunan province during2009and2010. Compared with the control Lin'aol, the average yield and daily output of Xiangkangyu2increased by9.60% and9.95%, respectively. Xiangkangyu2showed a significant yield increase than Lin'aol in all regional test sites. Compared with the control Dongdan16(drought sensitive) in the drought resistance contrast test, the DRC for major drought resistance parameters including grain yield, ASI, root depth, plant height and1000kernal weight were higher in Xiangkangyu2.
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