| Maize is not only one of the most important cereal crop over the world, but also is a leading cereal crop in China. High-oil maize is one of specialty maize, oil concentration of which is over 6% versus 4% around in normal maize. High concentration of oil and protein in maize kernel is desirable when maize is fed to livestock. Maize also produces a higher quality vegetable oil for high levels of unsaturated fatty acids. High-oil silages have consistent nutritional advantages over normal maize. Thus, the development of high-oil maize has been paid much more attention at present.With the advent of molecular marker technology, great efforts have been made in QTL mapping for concentration of oil, protein, starch and fatty acids, and for grain yields. All the materials used in previous study had the genetic background of IHO, however, the practical value of IHO has declined for many disadvantages. At the beginning of 1980's, Song began to develop the new high-oil maize germplasm with recurrent selection in China. A number of high-oil maize populations have been developed, whereas the molecular genetic basis of kernel chemical compositions is poorly understood.The objectives of the present study were to construct high-density genetic map by SSR markers, identify oil concentration QTL, as well as grain traits, with a large scale F2 populations derived from By804XB73 using composite interval mapping, evaluate these QTL effects, analyze their relationship among oil, protein, starch, and grain traits. These works will do great help to fine mapping for QTL associated kernel oil content, map-based cloning of these genes, and marker-assisted selection in high-oil maize breeding.The major results in this study are as follows:1. Totally, 439 SSR primers were employed to screen polymorphism between two parents, By804 and B73. Only 153 markers (34.85%) were co-dominant segregation. Ultimately, 151 SSR markers were assigned to 12 linkage groups using Mapmaker3.0. A total length of the linkage map equals to 1759.1 cM, with an average interval of 11.65 cM, which is consistent with the maps previously reported. A total of 37 markers showed a distorted segregation from the expected ratio (1:2:1).2. In F2 populations, 27 QTL were significantly associated with kernel oil concentration by composite interval mapping. The phenotypic variation explained by a single QTL ranged from 1.74% to 17.51%. 18 QTL were detected in F2 seeds and 21 QTL were in F3 seeds. 12 of 27 QTL (44.44%) were detected in the same or similar confidence intervals in both F2 seeds and Fa seeds.3. In F2 seeds, of 18 QTL associated with oil concentration, five QTL(27%)showedadditive effects, seven QTL (39%) showed partially dominant effects, one QTL (6%) showed dominant effects, and 5 QTL (28%) showed over-dominant effects. In F3 seeds, three QTL (14%) showed additive effects, 13 QTL (62%) showed partially dominant effects, two QTL (10%) showed dominant effects, and three QTL ( 14%) showed over-dominant effects. Effect of partial dominance as well as additive appears to play an important role in controlling kernel oil concentration.4. One of oil QTL, oilcl-2, located on chromosome 1 and linked to flanking markers, umc1122 and bnlg2086, had the great LOD value of 18.53/21.63, also explained 15.87%/17.51% of phenotypic variation. It seems to be an important major effect oil QTL.5. In p2:3 lines, with composite interval mapping, a total of 73 QTL were detected for different grain traits, nine QTL for kernel length, 12 QTL for kernel width, eight QTL for the ratio of kernel length to kernel width, 11 QTL for 100-kemel weight, for ear diameter, eight QTL for ear length, and five QTL for row number. Several QTL for oil concentration, kernel chemical compositions and grain yields clustered in common regions which were mainly on chromosome 1, 2, 3, 4, 7.6. Of 27 QTL for oil in this study, eight QTL had the same or similar confidence intervals as /to those QTL for oil concentration in experimental materials with different genetic backgroun...
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