Fine Mapping Of A Dwarf Gene ED1 In Brassica Napus L.

Rapeseed is one of important oil crops with great economic benefit and development potential.Rapeseed variety is easy to lodging with higher plant height leading to lower harvest index and yield.Meanwhile,rapeseed variety with high plant architecture is not suitable for machine harvesting,which improves the cost of planting rapeseed.Therefore,reasonable reduction of plant height is an important way to increase rapeseed yield and promot machine harvesting.The dwarf gene can effectively reduce the plant height and utilization of semi-dwarf genes greatly increased the yield of rice and wheat.The dwarf resources of rapeseed are insufficient and the mechanism of rapeseed plant height regulation lags behind.So,it is significant for rapeseed dwarf breeding to develop new dwarf resources and clone the related genes as well as explain their mechanism.In our study,a rapeseed mutant ed1（extremely dwarf 1）was obtained from natural mutation that exhibiting extremely dwarf.We analyzed the phenotype and agronomic traits of ed1 as well as combined with the observation of tissue slice to elucidate mechanism of dwarf.Meanwhile,we analyzed the inheritance of ed1 and constructed ed1×Y96 combination as mapping population.The dwarf gene was fine mapped using InDel and SNP molecular markers.The main results are as follows:（1）At mature stage,the plant height of N370 is 177cm and ed1 is 23cm,which is about 13.7%of that of N370.Compared with N370,leaves of ed1 were smaller and wrinkled with dark green color.There were fewer branches and shorter siliques as well as lower branch height.The plant height of F₁ derived from ed1×N370 is about 64 cm,which is lower than the median value of parents.The leaf size,degree of curling,root length,branch height and number of branches of F₁ were also between ed1 and N370.（2）Paraffin section of stem and leaf showed that pith cells in ed1 failed to form normal cell line compared to N370.The size of pith cells and parenchyma cells were smaller.The diameter of veins decreased to the half of N370,and the size of vascular cells and leaf cells became smaller.These results indicated that the smaller cells might be resulting the dwarf phenotype.（3）Spraying the exogenous IAA and BR to ed1 and N370 showed that ed1 did not restored to the wild-type phenotype,and there was no obvious change in leaf phenotype and plant height.While the leaves of N370 were bigger after spraying the exgenous hormones.Therefore,we believe that the synthesis pathway of IAA and BR in ed1 is normal.The measurement of endogenous hormones content showed that there is no significant difference in BR content between ed1 and N370,but the content of IAA in ed1 is twice that of N370.Subsequently,we treated ed1 and N370 with different concentrations of IAA and measured the length of hypocotyl.Hypocotyl was shortened under high concentration of IAA treatment in N370.There was no obvious change in the length of hypocotyl of ed1.Thus,ed1 is insensitive to IAA.Taken together,we hypothesized that the dwarf phenotype of ed1 might be related to the IAA signal transduction pathway.（4）The result of genetic analysis indicated that the leaf phenotype was linked to the dwarf which is controlled by a single semi-domidant gene.We constructed the ed1×Y96 F₂ population to isolate the mutant gene,and the target gene was eventually located in the 350kb region on chromosome C05 using750 homologous recessive individuals combined with In Del and SNP markers.Gene prediction showed that this region contains 14 ORFs.