QTL Mapping And Analysis For Leaves Water Use Efficiency And Its Related Traits In Maize

Maize (Zea mays L.) is an important cereal crop to both human and animal consumption. The maize yield is very important for solving the food security problem of our country and even the world. However, due to the growing shortage of global water, drought has severely limited the stability and increase of corn yield. Therefore, improving drought-resistance and water-saving of maize is imperative. With the gradual and further scientific research and production practice, it is particularly important by selecting and breeding the maize varieties with the high water use efficiency, to improve their capacity of drought-resistance.In recent years, the high-density genetic mapping of maize continued to be improved, the statistical methods of molecular biology is continuously updated and combined with molecular markers, thus, a large number of the quantitative trait loci (QTL) in maize was located, and these are solid foundations to molecular genetic research and molecular marker assisted breeding in the maize high water use efficiency.There were 23 maize inbred lines in this experiment. Two inbred lines, 444 and Mol17, were selected by measuring and analysis of their leaf water use efficiency (LWUE), and were used as parents to construct genetic population. A genetic linkage framework map with SSR and ISSR markers was constructed with DNA samples from F2 individuals derived from the cross 444 and Mo17. The field evaluation was conducted on the corresponding F2: 3 family under normal-irrigation (W) and moderate water-stress (WS). The QTL of LWUE was detected, the QTL mapping was performed by interval mapping method of software Map QTL 4.0. Furthermore, 26 indicators (morphology, physiology and biochemistry and production factors) were measured, and selected the property indexes closer relationship with LWUE by correlation analysis, and mapping and analysis the QTL of these indicators. The major results are as follows:1. Screening two inbred lines with larger difference of the LWUE. Inbred lines 444 was one of parents with high LWUE, inbred lines Mo17 was another with low LWUE. 190 F2 individuals, derived from the cross 444 and Mo17, was used to construct a genetic linkage framework map. 190F2: 3 family was used to locate QTL.2. Screening 14 indicators were significant or highly significant correlation with the maize LWUE: 4 physiological indexes, Pn,Tr,Gs and Ci;3 Chlorophyll a Fluorescence Parameters, Fo,Fv/Fm and Fv/Fo; 3agronomic characters, EH,TBN and ASI;4 yield component factors, EKW,ERN,EKN and BTL. Respectively.3. The framework linkage map was consisted of 181 markers (144 SSR markers and 37 ISSR markers); it spanned a total of 1442.0cM with an average interval of 8.0cM; the largest average genetic distance between markers was 32.0cM and less than 1cM.4. 60 QTLs were detected under two water treatment, and distributed in the10 chromosomes. 9 QTLs on chromosome 1, 6 QTLs on chromosome 2, 8 QTLs on chromosome 3, 7 QTLs on chromosome 4, 6 QTLs on chromosome 5, 4 QTLs on chromosome 6, 3 QTLs on chromosome 7, 8 QTLs on chromosome 8, 3 QTLs on chromosome 9 and 6 QTLs on chromosome10. Range of LOD values was from 2.8-5.65; individual QTL could account for 6.9—34.2%.5. Under normal irrigation conditions, 2QTLs for LWUE on the chromsomes1and 4; 3QTLs for Pn on the chromsomes1and 4(2); 3QTLs for Tr on the chromsomes1,4and7; 3QTLs for Gs on the chromsomes1,2and4; 2QTLs for Ci on the chromsomes5and9; 1QTLs for Fo on the chromsomes5; 1QTLs for Fv/Fm on the chromsomes6; 1QTLs for Fv/Fo on the chromsomes8; 3QTLs for EH on the chromsomes1,4and10;3QTLs for TBN on the chromsomes2,5and7; 2 QTLs for ASI on the chromsomes8and10; 3 QTLs for EKW on the chromsomes5,7and8; 1 QTLs for ERN on the chromsomes6; 3 QTLs for EKN on the chromsomes1,2and10; and 2QTLs for BTL on the chromsomes2and8.6. Under water-stressed condition, 3QTLs for LWUE on the chromsomes2,3and4; 2QTLs for Pn on the chromsomes6and8; 1QTLs for Tr on the chromsomes1; 1QTLs for Gs on the chromsomes10; 1QTLs for Ci on the chromsomes10; 2QTLs for Fo on the chromsomes3and8; 2QTLs for Fv/Fm on the chromsomes1and3; 2QTLs for Fv/Fo on the chromsomes1and3; 1QTLs for EH on the chromsomes8; 2QTLs for TBN on the chromsomes5and10; 3 QTLs for ASI on the chromsomes8and2,3and9;2 QTLs for EKW on the chromsomes3and5; 1 QTLs for ERN on the chromsomes6; 2 QTLs for EKN on the chromsomes3and9;and 2QTLs for BTL on the chromsomes3and8.