Analysis And QTL Mapping Of Seed-Setting Related Traits In Brassica Napus L.

Rapeseed is one of the major oil crops in China. It is the primary objective to increase oil production per unit through the improvement of yield and oil content of rapeseed in the current rapeseed breeding. This study was focused on analysis of seed numbers and weight in the lower and upper parts of the main inflorescence of Brassica napus. A genetic map was constructed with a doubled haploid (DH) population to map seed yield per plant and other related traits as well as three quality traits including protein content, oil content, and the total glucosinolate content. The main results are as follows:1. A genetic linkage map of Brassica napus with SSR markers mainly was constructed. The map includes 488 markers, and contains 19 linkage groups with the total length of 2956.3cM, average marker distance of 6.06cM. The constructed map is in good agreement with published maps.2. The following traits were examined: plant height, first branch number, branch height, length of main raceme, pod length (upper and lower section on main raceme, expressed as Upper and Lower thereafter), grain number per pod (Upper and Lower), seed weight on the main raceme (Upper and Lower), grain yield per plant, grain weight. All the traits showed a normal distribution and the phenotypic differences among genotypes reached a significant level. The heretabjilities of the traits vary in a range of 42.34%-81.64%. Except the total number of pods per plant, the correlations of the same trait at different locations as well as the correlations between different traits in the same location are significant. The heritability of upper pod length is higher than lower pod length while the lower grain number and grain weight have higher heretabilities than the upper parts. Yield per plant and plant height, first branch number, grain number (upper and lower), weight (upper and lower), the main inflorescence length of main raceme was significantly correlated with a high degree of branching and pod length (the upper and lower) were not significantly correlated;3. Analysis between the upper and lower parts of protein content, oil content and total glucosinolate content showed that upper and lower parts of the characters were significantly different in two years. For a same trait, two parents showed large difference in different years, but no significant difference between F1 performances. Oil content was more affected by the environment than the protein content and total glucosinolate content;4. Using composite interval mapping and LOD=2.5 as the critical value QTL for the upper and lower parts of pod length, seed numbers and seed weight and other related trais were investigated positioning 2008 and 2009. In total,92 QTLs were detected for above studied traits. The mapped QTL contributed to trait variation ranging 3.93%-25.09% with the LOD value range of 2.51-15.61. Total 30 QTLs were detected for quality traits, contributing to the variation of 3.93%-25.09% range with LOD values range of 2.54-14.44. Total 26 QTLs were detected for flowering date and related traits, contributing to the variation of 3.54%-17.77% with the LOD value range of 2.59-10.75. Over all 148 QTLs are located in different linkage groups and some of the QTLs can be repeatedly detected in two years.