Study On QTL Associated With Waterlogging Tolerance And Drought Resistance During Seedling Stage In Brassica Napus L.

Waterlogging and drought are serious environmental stresses on the growth of crop, which are the main abiotic constraints in oilseed production. In this study, we employed two B.napus lines which are different in tolerance to waterlongging and drought stress. The population with 150 doubled haploid (DH) lines was derived from the microspore culture of F₁. Testing experiments with 3 replicates following a randomized complete block design were implemented in two environments. Molecular markers were used to analyze the genetic model associated with 5 traits, WTC (waterlogging tolerance coefficient) and DRC (drought resistance coefficient) of all the traits. The main results are summarized as follow:1. Comparing two parents, the female parent (No2127-17×275B F4) is more tolerant to waterlogging and drought stress than the male parent (Huyoul 5×5900 F₄).2. A genetic linkage map, spanning 1489.4 cM with an average interval of 4.4 cM, was constructed using 183 simple sequence repeat (SSR) markers and 157 Amplified fragment length polymorphism (AFLP) markers. Based on the public information of microsatellites (SSR markers), our map was aligned with reference maps.3. In the DH population, 86 markers (25.3%) skewed from the expected 1:1 genotypic segregation by Chi-square test, and most of them skewed towards the male parent. The allele frequencies of the male parent and the female parent in all 340 informative loci were 52.7% and 47.3% respectively. The allele ratio approximated to the expected 1:1.4. Most traits in DH population showed transgressive segregation and demonstrated the normal distribution.5. Using composite interval mapping method, a total of 45 QTL were detected for five traits, which are plant height, root length, shoot dry weight, root dry weight and total dry weight, under control and waterlogging condition. Twenty eight QTL were detected under control and 26 QTL were detected under waterlogging condition. There are 9 QTL detected under both control and waterlogging condition. The other 11 QTL were detected by WTC.6. The entire genome was searched for QTL conferring significant effects on all scored traits by composite interval mapping in DH population. A total of 50 QTL were detected for five traits under control and drought condition. Twenty eight QTL were detected under control and 31 QTL were detected under drought condition. There are 9 QTL detected under both control and waterlogging condition The other 19 QTL related to DRC were identified. 7. QTL detected for five traits, WTC and DRC are clustering. All clusters detected indicated that the waterlogging tolerance and drought resistance may have strong relationship, which implied that waterlogging tolerance and drought resistance can be pyramided in breeding in B. napus.