| Yield still was the main target of corn breeding in China. Using density tolerance varietiesand relying on population production to improve yields was the most economical and effectiveway to complete higher yield. It was the inevitable trend and development direction of cornbreeding and industrialization in future. In this study, a four-way cross population was built withfour inbred lines (Zheng58, PH6WC,Yu87-1, Zi330).The genetic linkage map was constructed bySSR markers. The density tolerance and related traits QTL was detected in both high and lowdensity in two test point. The major results were as follows:1. The density tolerance of15inbred lines was indentified in the high and low density withdensity tolerant coefficient (DTC).The results showed the DTC of the15inbred lines have alarge amplitude value. The top5inbred lines with high density tolerant ranked as: PH6WC>Zheng58> K12> Ye478> Shen137，these inbred lines have strong density tolerance. The last5inbred lines with high density tolerant ranked as: Zi330<87-<Zong3<1<Xu178Dan9046，these inbred lines sensitive to the density. Correlation analysis of the F2:3families in Guang zhouand San ya two test points showed that DTC has a significant positive correlation (0.342**) in thetwo environment. It indicated that the DTC calculated based on the individual production as ameasure of corn density tolerance is feasible and reliable. In the high density of the two test points,PH (0.131*,0.156*)，SD (0.1488*,0.152*) and LO (0.141*,0.132*) had a significant positiverelated between DTC; EL (0.245**,0.161*)，KRE (0.243**,0.237**) and HGW (0.224**,0.168*) had a significant or very significant positive related between DTC;there was a significantnegative correlation between BTL and DTC. Therefore, these traits can be used as an importantsubindicators for evaluating the density tolerance.2. A genetic linkage map containing231SSR markers was constructed based on an four-waycross F1population with228individuals. The map spanned a total of1387.2cM with an averageinterval of6.19cM, the average interval from4.05to9.29on the10chromosome. For the study of231markers, there are225markers in accordance with the rate of1:1or1:1:1:1or1:2:1in thesegregation population. A linkage groups were established, covering the whole10chromosomes.The map can meet the preliminary requirements for the QTL mapping.3. The DTC from the population of the four-way cross F2:3families were evaluated for QTL analysis, with the method of interval mapping,9QTL were indentified for DTC on chromosome3,4,7,8, and the phenotypic variance explained by each QTL ranged from5.2%to28.9%. A majorQTL was found on chromosome7fall on the same marker interval, located in bin7.02-bin7.03site, were detected in both Guang zhou and San ya environment stability. Two QTL detected onchromosome3in the two environment, qDTC-E1-1and qDTC-E2-2near the markerumc1399,these position in the linkage map is very close, located in bin3.07-3.09andbin3.05-bin3.07site of the linkage map, respectively.4. Hundred and eighty-four QTL for14traits related to the density tolerance were detectedin the two density and two test points. There were screened mainly distributed in4,6,7and8chromosome. The phenotypic variance explained by each QTL ranged from3.32%to28.9%.Planttype QTL were mainly located on chromosome1,4,7,9. Lodging resistance QTL were mainlydetected on chromosome1,3,8. Ear traits QTL were mainly distributed in4,6,7,8chromosome.Part of QTL clusters on the part of the region on partial region on chromosome.Twenty-six QTL were detected in at least two environment, in which7were detected underdifferent density,19stable QTL were detected under different test points,22major QTL hasphenotypic contribution rate greater than10%simultaneously detected in two or moreenvironment. Three environmental insensitive QTL were detected in4environments. Oneenvironmental insensitive QTL qLO-E1-1was found on chromosome1located bin1.02site,controlling the leaf orientation; environmental insensitive QTL qTBN-E1-3was detected onchromosome5located bin5.00-bin5.01site; environmental insensitive QTL qSDC-E1-3wasdetected on chromosome3located bin3.01-bin3.02site.The result of this study may provideuseful information for compact breeding and marker-assisted selection for maize．... |
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