Quantitative Trait Loci Mapping On Flowering Time Of Soybean

Soybean[Glycine Max（L.）Merr.] is an important crop for grain,oil and feed.As economy and graziery develops,native need of soybean grows as well.However,either planting area or total production of soybean in our country is about to decrease recently,which makes soybean imports increase continuously.Statistics show that our country product 16 million tons while imported 83.91 million tons of soybean.Although massive import can satisfy present demand of soybean,it also can threat development of soybean planting and linked farmers.It makes soybean industry and protein demand of our country at stake.If we rely most of soybean conduction on import,both our plant oil and protein industry and graziery would be under control of international market,which is extremely instable.To relieve the strike,we must improve production of soybean,which can be helped achieve by expanding planting area.Soybean is a typical kind of short-day crop,which is extremely sensitive to change of light condition.Productive kind of soybean which grows in North-China under long-day condition would flower earlier if planted in South-China under short-day condition,which could lead to lower production.This feature limits competitiveness of soybean in South-China which leads to decrease of planting area of soybean because farmers would always choose more productive crops to plant.It makes mapping Quantitative Trait Loci（QTL）linked to flowering time essential.This work could offer theoretical basis to sieving insensitive kind of soybean and make planting soybean in South-China easier,which is beneficial to improve production of soybean.The research about flowering time of soybean under SD（Short Day）is not enough so far,which can be perfected by our results.We took two kinds of plant materials to map QTL about soybean flowering time under SD,which are Recombinant Inbred Lines（RILs）constructed by hybrid of BD2 and BX10（named group BDBX）and group of EBH constructed by hybrid of Harosoy and BR121.As for group BDBX,we recorded their flowering time under SD on 2015 and 2016.Then we took 277 of molecular markers to help mapping linkage group and finally to map QTL about flowering time of group BDBX under SD.As for group EBH,which were constructed to locate gene J which is linked to long juvenile trait of soybean.However,we found that when gene J is heterozygous in this group,there are 62 EBH groups showed ratio of 15:1 on flowering time.Then we deduced that there is still one gene that influencing flowering time of picked EBH group.So we chose seeds which are j homozygous from the 62 EBH group and planted all of them and recorded their flowering time under SD.Then we got 3 groups which showed ratio of 3:1 on flowering time and named EBH1301,EBH1423 and EBH1350.Finally,we mixed their DNA extracted from the group which are extremely early and extremely late on trait of flowering time and predicted possible place of linked loci by Bulked Segregant Analysis sequencing.Here are detailed results:1.Mapped three QTLs linked to flowering time: q FT-B2 with LOD of 1.87 in chromosome 14 which located in Satt063-Satt560,q FT-H with LOD of 3.06 in chromosome 12 which located in Satt192-Sctt009 and q FT-K with LOD of 2.78 in chromosome 9 which located in Satt549-Sat₀87.2.Found and cloned 5 genes between BD2 and BX10 in QTL locations,which are Glyma.09G003400_FTIP,Glyma.09G007500_STM in linkage group K,Glyma.12G033100_MSl1 in linkage group H,Glyma.14G174200_CRY1 and Glyma.14G183800_AGL16 in linkage group B2.By sequencing,we found there are differences between BD2 and BX10 at 3064 bp of FTIP and 2005 bp,3069bp and 3289 bp of CRY1.3.Through BSA（Bulked Segregant Analysis）sequencing,we located loci which is significant correlated to flowering time about EBH 1301 group on ID10403.Furthermore,we preliminary proved that gene E2 is also significant correlated to the trait.