| Boron (B) is an essential mineral nutrient for plant growth and development. Brassica napus needs more boron for its growth, however the main production area of Brassica napus in China is deficient in soil available B, B deficiency can be alleviated by applying boron fertilizer. Based on the identification a lot of rapeseed cultivars with different genotype, we found that considerable genotypic variations in response to B deficiency exist among rapeseed varieties and the B efficiency was controlled by multiple genes. For QTL mapping and the genetic improvement for the trait tolerant to low B stress, this study was involved in constructing a double haploid population derived from a cross between B-effcient parent Qingyou 10 (QY10) and B-inefficient parent Westar by microspore culture, developing a genetic linkage map with SSR (Simple Sequence Repeat) and AFLP (Amplified Fragments Length Polymorphism) markers, analysing of QTLs based on the investigation of some traits related to B-efficiency at seedling stage with solution culture under low B levels. The main results were shown as follows:1. Constructing a B-efficeincy double haploid populationB-inefficient cultivar Westar, B-efficient cultivar Qingyou 10 and its F1 plants were selected as materials for microspore culture. The results showed that the ratio of embryo development was influenced by external environment, culture condition, colchicine treatment and so on. At last, a Brassica napus B-efficient double haploid population contained 81 lines, named QW DH population were constructed.2. Developping the genetic linkage mapA genetic linkage map was developped with the QW DH population by SSR and AFLP molecular marker using JionMap 4.0, which included 652 markers (478 SSR markers and 174 AFLP markers). The map had 20 linkage groups with an average length of 2.74 cM and covered a total of 1785.57 cM.3. Analysising some physiological traits related to B-efficiencyUnder low B level (0.25μM B), the B-inefficient parent's leaves got severely curve, the colour became deeper, and the root yellowed with black dot on root tips, but B-efficient parent grew normally. QY10 grew better than Westar in root length, dry weight, B accumulation etc. Under normal and low boron levels, evident differences among lines of the QW population were detected, and transgressive segregation was found.4. Mapping QTLs related to B-efficiencyBy QTL mapping software of WinQTLCart 2.5, a model based on the composite interval mapping,38 QTLs significantly related to 14 traits were identified on 13 linkage groups. LOD of the detected single QTL range from 3.17 to 11.66; the contribution of single QTL in explaining the phenotypic variation in the population ranged from 8.17% to 41.26%. Compared the loci distribution on the linkage groups, many QTL pairs related to different traits located on the same linkage or overlapped, which indicated that QTLs related to B-efficiency were pleiotropic. |
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