Identification Of Quantitative Trait Loci For Seedling Root Traits Of Maize Under Drought Stresses

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 maker linkage map was construct with DH population derived from "Nong xi110 × Nong xi531" by 146 SSR markers;then 82 DH lines were identified for drought tolerance under two water regimes(normal control and water stressed);in the end quantitative trait loci (QTL) associated traits related root were identified and analyzed in this study.The major results are as follows:1. The major traits ( root fresh weight, root dry weight, ratio of fresh root to shoot, ratio of dry root to shoot, maximum root length, semina root numbe and adventitious root number ) related to drought tolerance of 82 DH lines were surveyed and analysed under two water regimes. Under two water regimes,the average values of all traits are significant difference among lines;which may be used for QTL mapping. Under water stressed condition,the variance coefficient of root traits have increased than well-watered conditions but ratio of fresh root to shoot.2. A genetic linkage map containing 146 SSR markers was constructed,which spanned a total of 2055.9 cM with an average interval of 14.08 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. All the marker loci were tested for genetic segregation, and two segregation distortion regions were found on the chromosomes3,7.4. 17 QTL were detected for 7 root traits under two water regime. Under water stress condition, 11 QTL were detected;and under well-watered condition 6 QTL were detected.Each traits have been identified 1-2 QTL which were responsible for interpreting 2.00-42.31% of the phenotypic variance individually,but adventitious root number have been not detected any QTL;and showed additive effect and additive- additive epistatic.5. Compared the results with other researchers reports,the chromosome 1 and 9 have higher frequency of QTL associated root traits.