Shan Zhihui

QTL Analysis of Yield,Yield Components,and Lodging in Soybean

To date,more than 80 QTLs for yield have been mapped on 18 linkage groups of soybean(Glycine max L.Merr.) using over 20 segregation populations.However,only QTLs that expressed stably in different populations and environments are of great value for soybean breeding.Except for QTLs associated with seed weight,there are few reports on QTLs for other yield-related traits.The objectives of this study were to detect yield-related QTLs in soybean and to compare linkage groups obtained from different mapping populations.A total of 165 recombinant inbred lines(RILs) derived from a cross between Zhongdou 29 and Zhongdou 32 were used to analyze the relationships of yield per plant,yield components,and lodging percentage as well as their genetic effects,and to map the QTLs in 2006-2007.Thirty-eight QTLs for yield,seed and pod traits,and lodging related traits were detected using composite interval mapping(CIM) method.Most of the QTLs were located on C2,F,and I linkage groups.QTL qLD-15-1 for lodging percentage on F linkage group was detected in both years,which explained more than 20% of the phenotypic variation.This QTL had the same or adjacent marker intervals to QTLs for 100-seed weight and pod number on branch,showing correlation between yield-related traits and lodging.On I linkage group,the QTLs for seeds per pod,two-seed pods,three-seed pods,and four-seed pods were detected on the same position across years and explained 32-65% of the phenotypic variation.The positive alleles at loci of seeds per pod,four-seed pods,two-seed-pods,and three-seed pods were from different parents.The four QTLs for seed and pod traits mapped on the same position,which was consistent with the correlation analysis result of phenotypic traits.This suggests that the regulatory mechanisms of the four traits for seed and pod are different.

QTL analysis of lodging and related traits in soybean.

Lodging is an important agronomical trait in soybean,which has obvious negative effect on yield,seed quality and mechanical harvesting efficiency.The 165 recombinant inbred lines(RIL) derived from a cross between Zhongdou 29 and Zhongdou 32 were used in two years,with the composite interval mapping(CIM) method to identify the QTLs associated with lodging,plant height,stem diameter,nodes on main stem,branch number,shoot weight,root weight and stem intension.On link-age groups A2,C1,C2,D1a,F,G,I,and L,25 and 19 QTLs for lodging and related traits were detected in 2006 and 2007,re-spectively,explaining 4.4–50.1% phenotypic variation.One QTL(qLD-15-1) of lodging and one QTL(qPH-15-2) of plant height on F linkage group were both detected in two years;one QTL of nodes on main stem and two QTLs of root weight were detected in two years on G,A2,and L linkage groups respectively.The positions of some QTLs of plant height,root weight,shoot weight,stem diameter,nodes on main stem and branch number were close to those of lodging,showing that the lodging resistance is asso-ciated with the characters in aerial part and underground portion,the results were consistent with the correlation analysis of phe-notypic traits,showing the correlation of these morphological traits in genetics.The QTLs of some traits had the same positions,but were not both detected in two years.

Identification of photoperiod-regulated gene in soybean and functional analysis in Nicotiana benthamiana

Soybean (Glycine max) is a short-day crop and the photoperiod is a crucial factor regulating its flowering time. To investigate the molecular mechanism controlling the flowering time by photoperiod in soybean, cDNA-amplified fragment length polymorphism (cDNA-AFLP) was used to identify photoperiod-regulated genes in leaves of soybean growing under short-day length, neutral photoperiod and long-day length. A total of 36 transcript-derived fragments (TDFs) were identified to be regulated by photoperiod. Among them, 26 TDFs were homologues of genes with known function. These genes are involved in secondary metabolism, cellular metabolism, cell wall components metabolism, ion transport and hormone signalling. Silencing of the homologue genes in Nicotiana benthemiana for 14 TDFs was conducted by virus-induced gene silencing. The flowering time was delayed by silencing of the genes encoding rhodanese and 40S ribosomal protein S4 (RPS4). The results indicated that rhodanese and RPS4 probably play important roles in regulating flowering time.