Mapping And Application Of QTLs For Important Agronomic Traits In Soybean

In China,soybean（Glycine max L.Merr）is a kind of food crop with high economic value and high nutritional value.In this era of health awareness and rising living standards,the diet of residents is very different from the past.In recent years,China’s demand for soybean has been growing,among which,imports account for more than 80%of the total consumption.Excessive reliance on imports has resulted in a significant decline in the market competitiveness of our soybean product industry.It is an important task for Chinese soybean researchers to alleviate the influence of foreign soybean on Chinese soybean industry,meet the domestic soybean supply,increase the yield of soybean,and cultivate new varieties of soybean with high yield and high quality.Ideal plant type is the constituent factor of high yield potential of soybean,and plant height,stem diameter and main stem node are closely related to crop quality and lodging resistance.The improvement of soybean plant type is a key measure to achieve high yield of soybean,while stem diameter is a major component of soybean plant type.To some extent,it can also significantly improve the lodging resistance of the plant,thus improving the yield of soybean.However,there are few researches on the soybean stem diameter.In order to provide gene resources and theoretical references for molecular design breeding of high yield and high quality soybean,this paper tries to explore functional sites or genes of excellent soybean plant types.The main results are as follows:（1）Williams 82 and Dongnong 50 were used to construct F₂ populations.Williams 82 was tall and its plant type was open.The soybean variety Dongnong 50 is short and its plant type is convergent.There were significant differences in plant height,stem diameter,stem node number,branch number and pod number between Williams 82 and Dongnong 50 which were used as parents.The F₂ population of Williams 82 and Dongnong 50 contained 247 families and the results showed that the characters of their offspring in F₂ population were obviously separated.Meanwhile,the frequency distribution,kurtosis and skewness trends of eight important agronomic traits in F₂ population were consistent with the genetic rule of a quantitative trait controlled by multiple genes.（2）A total of 41 plant type related QTLs were identified:41 QTLs were identified by genotyping sequencing（GBS）,including one plant height related QTL,four QTLs related to stem diameter,five QTLs correlated with the number of main stem segments.Also,there were five one-pod correlated QTLs and 11 binder-pod correlated QTLs,seven three-pod correlated QTLs,six four pod and two branch number correlated QTLs,which provided a theoretical basis for soybean molecular design breeding.（3）Five genes that may be related to stem diameter were screened.In terms of stem diameter,QTL locus on chromosome 2 of soybean was selected for study and its physical location was between 27220826 and 28485074.Through functional annotation of 24 candidate genes in the confidence region of the rough QTL,it was found that they were closely related to multiple biological processes such as material and energy metabolism,cell and organ development and formation.Based on the function annotation,we predicted the expression patterns of the 24 genes in different tissues and analyzed the expression levels in both parents.Finally,five genes containing Glyma.02G167100,Glyma.02G167700,Glyma.02G168100,Glyma.02G168500 and Glyma.02G169000 were inferred to affect the formation of ideal plant type and lodging resistance of soybean.