A Dissertation Presented To The Academic Degree Committee Of Sichuan Agricultural University In Fulfillment Of The Requirement For The Degree Of Doctor Of Philosophy

Drought is the most important abiotic factors limiting maize production. The effective approach to solve this problem is breeding and popularizing variety for drought tolerance. However, conventional selection for drought tolerance is inefficient because that drought tolerance is a complicated quantitative trait and required special environment to identify. With the development and application of molecular markers, MAS(molecular assistant selection) supply a useful tool to the breeding for drought tolerance. In order to investigate the molecular genetic basis of drought tolerance and find useful information for genetic improvement to drought tolerance further, molecular marker linkage map was construct with F2 population derived from N87-l(drought tolerance) 9526 (drought sensitive ) by 103 SSR markers; then 183 F2:3 family lines were identified for drought tolerance under two water regimes(normal control and water stressed); in the end, quantitative trait locus(QTL) associated traits related to drought tolerance were identified and analyzed in this study. The major results are as follows.1. The major traits(grain yield , male flowering, female flowering, anthesis-silking interval, plant height, ear height, ear leaf length, ear leaf width, root number, root weight, tassel branch number, tassel main axis length ) related to drought tolerance of 183 F2:3 family lines were surveyed and analysed under two water regimes. Under two water regimes , the average values of all traits are significant difference among family lines,which may be used for QTL mapping; most of these traits are significant positive correlation with yield ,but ASI has significant negative correlation with yield, under water stressed condition, yield and ASI, root weight and tassel main axis length may be used for important second drought tolerance indexes.2. A genetic linkage map containing 103 SSR markers was constructed, which spanned a total of 1512.9 cM with an average interval of 16.9 cM. Compared with other published maize linkage maps in chromosome bin locus, the linkage map established in this study was consistent with them. The SSR linkage can be used for QTL mapping.3.By composite interval mapping(LOD 2.0),82 QTL were detected for 12 traits under two water regime and 7 QTL were detected for DTI. Under water stress environment,39 QTLwere detected; and under normal environment 43 QTL were detected. Each traits have been identified 1~7 QTL which were responsible for interpreting 4.68-34.1% of the phenotypic variance individually, and showed partial dominant effect and over dominant .QTLs of grain yield and anthesis-silking interval, ear height, ear leaf length, ear leaf width and root weight are relatively consistence across two environments4. This result also show that some QTLs trend to cluster the same chromosome region. The key chromosome regions for drought tolerance mostly lie on following chromosome: chromosome 1, bnlg2086(binl.04) and bnlgl347(binl.lO);chromosome4, umc 1117~nc005(bin4.04~bin4.05) and bnlg2126~umcl573(bin4.08~4.09);chromosome5, bnlgl 006~umcl416(bin5.0);chromosome6,umcl296(bin6.06~bin6.07);chromosome7,phi034~bnlg 1792(bin7.02)and bnlgl805~umc1015 (bin7.03) .5. Compared the results with other researchers' reports, the chromosome 4 of N87-1 genomic have higher frequency of QTLs associated drought tolerance.