QTL Mapping Of Important Agronomic Traits Of Soybean Stem Color And Multi-leaflet

Soybean（Glycine max L.）originated in China.As an important grain and feed crop,it is not only the main source of human plant oil and protein,but also an important source of animal feed protein.China is a soybean consuming country,and the gap between production and demand will exceed trillion tons in 2020,with an increasing trend year by year.Getting rid of dependence on foreign imports and further improving soybean production is one of the important problems to be solved urgently in China’s agriculture at this stage.Mapping QTLs of important agronomic traits and analyzing gene regulatory networks controlling soybean traits are one of the effective ways to achieve high yield and high quality of soybean.The soybean variety Williams 82 has a green stem character and belongs to the normal three-leaflet type;Soybean variety PI416892 has purple stem and belongs to multi-leaflet type;There were significant differences in plant height,stem diameter and number of main stem nodes.Based on the investigation and statistical analysis of six agronomic characters of F₂generation population of Williams 82 and PI416892,it was found that the stem color and multi-leaflet characters were separated.We constructed extreme phenotype mixing pools for these two characters respectively,and determined them through bulk segregant analysis（BSA）.The main QTL controlling the two traits were identified by SSR molecular marker development and recombinant single plant screening.The main results are as follows:（1）By constructing the mixed pool of soybean stem color extreme traits and cluster segregation analysis（BSA）,it was found that there was a QTL on soybean chromosome 13,with a physical location between 18836654 and 19769606（0.93 Mb）.Develop SSR molecular markers in the confidence region of QTL of soybean stem color traits,and find many pairs of DNA molecular markers with good polymorphism.SSR molecular markers were used to screen the recombinant single plant,and its confidence region was reduced to 0.26Mb（physical location:19147603～19408691）.There were 15 candidate genes in this region,and the expression levels of 15 genes in this region were detected in the two parents.It was found that the expression level of Glyma.13G082300 was significantly different both parents,and the expression in green stems was significantly higher than that in purple stems;Gene annotation analysis showed that Glyma.13G082300 was involved in regulating the synthesis of Flavonol Synthase（FLS）,which affects the content of anthocyanins;By measuring the anthocyanin content in the stems of parents,it was found that the anthocyanin content of purple stems was significantly higher than that of green stems.According to these results,Glyma.13G082300may be a candidate gene for controlling stem color of soybean.（2）Soybean leaves are generally three compound leaves,and some varieties or plant mutants have 4～7 leaflets,which are called multi-leaflets;Multi-leaflet varieties have good agronomic characters（disease resistance,lodging resistance,etc.）and are excellent soybean germplasm resources.By constructing mixed pool and cluster segregation analysis（BSA）of soybean multi-leaflet traits,it was found that there were two major QTL on chromosome 8,one of which was between 18923314 and 23430822,and the other was between 40452908 and42520231.Multi-leaflet soybean varieties have good quality and stress resistance.The results of this study provide a certain reference value for soybean high-quality breeding.（3）In addition,the phenotypic data of several agronomic traits such as plant height,stem diameter,node number of main stem and pod number per plant were analyzed in the hybrid population,and they showed obvious normal distribution,indicating that these traits may be quantitative traits controlled by multiple genes.In conclusion,this study constructed a hybrid population,investigated important agronomic traits in the population,identified QTL related to agronomic traits,and identified candidate genes for controlling stem color.This study provided important information for future research on important agronomic traits.