Dissertation > Agricultural Sciences > Crop > Economic crops > Oil crops > Rapeseed ( Brassica )

Genetic Analysis and QTL Mapping of Early Flowering Season in Brassica Napus L.

Author LouYanZhi
Tutor MaChaoZhi
School Huazhong Agricultural University
Course Crop Genetics and Breeding
Keywords B. napus L. Flowering time Amplified Consensus Genetic Marker Genetic linkage map Quantitative trait loci (QTL) mapping
CLC S565.4
Type Master's thesis
Year 2008
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Oilseed rapa is an important oilcrop planted extensively in the world. Flowering early or late, or days to flowering (DTF) will produce important impacts on the maturity, harvesting time and yield of seed. To our best knowledge, DTF is one quantitative trait with a complex genetic basis and regulated by endogenous flowering genes, hormone level, physiological and biochemical processes and environmental factors (mainly including photoperiod and temperature) together. Flowering time is controlled in a multiple gene form with locus variation between different varieties and affected by environment factors. Studies on flowering time may help breed varieties suitable to crop rotation and manipulate pollination control systems in hybrid breeding and production.In this study, we employed an F2 population resulting from crossing "06-6-7003×06-6-657", Field experiments were designed in two environments. Molecular markers were used to analyze the genetic model associated with flowering time performance. The major results are as follows:1. A total of 29 ACGM primer pairs were designed according to the different genes in flowering time of Arabidopsis. Of these, each of the majority (24) amplified a clear and strong band from the total genomic DNA of two parents when detected by 6% PAGE analysis, a total of 7 ESTs (Expression Sequence Tags) or genes from B. napus, B. rapa and B. oleracea showed polymorphisms between the parents of the mapping population, providing total 8 marker loci in the mapping population. These markers, respectively, located in the linkage groups N6, N12 and N13 of B. napus.2. 119 simple sequence repeat (SSR) markers, 131 amplified fragment length polymorphism (AFLP), 35 sequence-related amplified polymorphism (SRAP) markers and 8 ACGM markers were used to construct a genetic linkage map of B. napus. Under the condition of LOD≥3.0, a total of 214 markers were assigned to 23 linkage groups (LGs). This map covered 1865.00 cM with average marker interval of 8.45 cM. The public information of microsatellites (SSR markers), contributed to establish the links between the map of Parkin et. al (1995) and ours.3. In the F2 population, 29 markers (13.6%) by Chi-square test. There are 13 markers of SSR, 13 markers of AFLP, 2 markers of SRAP and 1marker of ACGM that skewed from the expected genotypic segregation and there are 13 markers (37.9%) of them skewed towards the female parent.4. Flowering time demonstrated the normal distribution in both environments. There existed significant difference in genotype of flowering time interval the F2:3 family line. There existed significant difference of flowering time in both environments. Environmental variance is more than genotypic variance greatly observed for floweringtime. Broad sense heritability of flowering time is 43.8%. There is significant positivecorrelation of flowering time in two environments.5. The entire genome was searched for QTL conferring significant effects on floweringtime by composite interval mapping in two populations. 7 QTL were detected offlowering time in He Zheng and 7 QTL were detected of flowering time in Wu Han.There were 2 QTL repeatedly detected.

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