Study On Gene Mapping For Plant-Type, Photosynthetic And Physiological, And Phosphorus Deficiency Tolerant Traits Associated To Yield In Soybean [Glycine Max (L.) Merr.]

Soybean [Glycine max (L.) Merr.] is an important crop in many diverse regions of the world,especially in China in which it has been cultivated for more than 5000 years.Yield improvement is one of the most crucial goals in soybean breeding program.In this investigation,on the basis of analyzing leading factor in yield improvements,QTLs mapping of plant-type,photosynthetic and physiological,and phosphorus deficiency tolerant traits associated with yield were conducted using two sets of RIL populations developed via single-seed descent (SSD) at China National Center for Soybean Improvement.The QTL mapping was done with the program WinQYLCart.The primary results are as follows:Brachytic stem is a specific trait in plant type of soybean and its yield potential may be higher under high population when compared with normal stem.NJ(SP)BN population was used to map genes and QTLs of three plant type traits (brachytic stem,determinate growth habit and plant height) and to identify the effects of brachytic stem on agronomic traits such as yield. The primary results indicated that brachytic stem (sb) and determinate growth habit (dtl) were mapped on linkage groups B2 and L,two major QTLs related to plant height were detected and mapped on linkage group L near dtl,and B2-1 near sb,and explained 52.5 and 11.6％of total phenotypie variation.Another minor QTLs for plant height were mapped on LG-C2 and N.QTLs with negative additive effects for plant height near dtl and sb also had negative effects on seed yield.Lines with brachytic stem had shorter plant height,lower apparent biological yield,seed yield,and apparent harvest index,and essentially no differences in days to maturity when compared with normal stem lines.It was obvious that the effect of brachytic stem on yield was-due to the decreased height, apparent biological yield and apparent harvest index.Improving seed yield is an important goal of soybean breeding programs.In the present investigation,NJRIKY and NJ(SP)BN populations were used to mapping QTLs for five agronomic and physiological traits including plant height,days to maturity,seed yield,apparent physiological yield and apparent harvest index,and correlation analysis among the five traits were also conducted.The results indicated there were 40 putative QTL significantly (P<0.05,LOD>2.5) associated with 5 agronomic and physiological traits in two sets of RIL populations and a number of coincident QTLs associated to seed yield and it related traits were observed.Among them, QTLs on LG-C2 and L were coincidence with many QTLs in early reports,however,few QTLs for plant height,days to maturity and seed yield were detected on LG-B2 and O before.Most of the BY QTLs co-located with SY QTLs,and all of the coincident showed the additive effects in the same direction. Three and four HI QTLs were identified and mapped on LG-DIa+Q,C1, C2,E and J in NJRIKY and NJ(SP)BN,respectively. Only one HI QTLs co-located with SY QTLs on LG-C2 in NJRIKY population,and this pair of co-located QTLs had additive effects in reverse direction.QTLs for plant height and days to maturity co-located with apparent biological yield and seed yield prominently,however,only one genomic region on LG-C2 existed co-located QTLs for plant height and harvest index with additive effects in the different direction.Chlorophyll content of plant leaf is an important trait associated with photosynthesis, as a major photosynthetic pigment and index of crop field management and crop breeding. In the current study,NJ(SP)BN population were used to detect quantitative trait loci (QTL) associated with chlorophyll content (CC) at four stages of development, and their correlation with five yield-related traits including seed yield,apparent biological yield, apparent harvest index, plant height and days to maturity were conducted.The primary results indicated that QTLs associated with the accumulation of chlorophyll content were detected and mapped on LG-B1,DIa+Q,F,G,H,L and M,each QTL explained 6.9％-23.4％of phenotypic variation.There are no QTLs detected to be expressed in tw year at the V6 and R2 stage of development. However,at the R4 stage four QTLs (qccF.1,qccG.2,qccH.1 and qccM.1) expressed in both years,and one of them (qccH.1) also expressed at R6 stage in two years.QTLs associated with the net increment of chlorophyll content were detected and mapped on LG-B1,B2,G,I and L,two of them on LG-B2 and L (qccB2-1.1 and qccL.1) expressed during R2 to R4 and R4 to R6,and co-located with QTLs for seed yield. These indicated that there are significant correlation between seed yield and chlorophyll content at late stages of development. Leaf senescence is a character of plant development,Delayed leaf senescence or stay green character has received considerable attention because of its negative impact on photosynthesis and its role in nutrient redistribution within the plant.NJRIKY and NJ(SP)BN populations were used identified QTLs associated with leaf senescence,and correlation between leaf senescence and yield traits were also conducted. The primary results indicated that four QTLs for leaf senescence were detected and mapped on LG-C1, Dlb+W,L and O,each QTL explained 5.8～13.7％of total variation.Leaf senescence significantly and positively correlated with apparent biological yield,seed yield, plant height and days to maturity in both populations except lower correlation with days to maturity in NJ(SP)BN. However,different correlation between leaf senescence and apparent harvest index were observed, negatively and significantly in NJRIKY and positively and significantly in NJ(SP)BN.These indicated that harvest index may be increased through the selection of delayed leaf senescence in soybean breeding,but breeding materials with high potential of yield couldn't be obtained.To increase photosynthesis rate had important role on yield improvement in crop plants such as soybean.In the present investigation,NJ(SP)BN population was used to identify QTLs associated with photosynthetic traits including photosynthetic rate,stomatal conductance,intercellular CO2 concentration and transpiration rate,and correlation among seed yield and photosynthetic traits were also conducted.The primary results indicated that one,two,one and two QTLs were detected to be associated with photosynthetic traits including photosynthetic rate,stomatal conductance, intercellular CO2 concentration and transpiration rate and mapped to LG-O,A1 and Dlb+W,G,H and M,respectively.Each QTL explained 8.0％-21.5％of phenotypic variation.No QTLs co-located each other. Correlation analysis showed there was lower relationship between seed yield and photosynthetic rate, significantly and positively correlations were observed among four photosynthetic traits except that between photosynthetic rate and intercellular CO2 concentration.Phosphorus (P) deficiency is a major abiotic stress that limits productivity of crops such as soybean throughout the world.In the current investigation,NJ(SP)BN population was used to detect quantitative trait loci (QTL) associated with P deficiency tolerance.The primary results showed that total dry weight under P-minus condition was determined by phosphorus uptake per plant,and no correlation between phosphorus use efficiency and total dry weight was observed.Phosphorus uptake per plant was Significantly and positively correlated with root dry weight and root efficiency,76.2％of variation of phosphorus uptake per plant come from root efficiency. Root to shoot ratio under P-minus condition increased significantly due to no significant change of shoot dry weight and significant increase of root dry weight.Ten QTLs associated with phosphorus deficiency tolerance were detected and mapped on LG-C2,Dlb+W,F,G,H,K2,L and N,each QTL explained 6.6～13.4％of phenotypic variation,positive alleles of three QTLs among them were from parent 'Bogao',and that of the other QTLs come from parent 'nannong 94-156'.