Abstract: Since soybean seed yield is the product of both biomass accumulation and harvest index, the objective of the present study was to measure the correlations of seed yield with the other two traits as well as with biomass accumulation at different seed development stages, to map their QTLs, and to reveal the QTL basis of the correlations. A RIL population, NJRIKY, derived from the cross between Nannong 1138-2 and Kefeng 1, quite diverse in biomass, harvest index and yield, was used to study the correla-tion among biomass accumulation, apparent harvest index and yield, to map the QTLs of the traits for revealing the genetic basis of the correlation among the traits. The results obtained were as follows: (1) Yield was closely and positively correlated with bio-mass accumulation and their correlation increased in the process of growth with the highest R2=0.76 at harvest stage. There ap-peared some negative exponential correlation between yield and biomass at R1, R3, and R5, with the biomass of 1 000, 2 300, and 5 500 kg ha^-1 as the highest turning point, respectively. A linear correlation of yield with biomass at harvest stage [BM (H)] was detected, but without upper limit of the biomass found in the present experiment. There was an exponential correlation between yield and apparent harvest index, with 0.42 as the turning point, positive relationship as less than 0.42 and negative relationship as larger than 0.42. (2) 9, 10, and 10 QTLs for yield, apparent harvest index and BM (H) were detected in NJRIKY and 2, 3, and 3 QTLs of them respectively detected in both years. In addition, 6, 9, and 6 QTLs for biomass at R1, R3, and R5 were identified in the population, respectively, with 2 of them being detected across R1 through R5 in both years. (3) Among the 9 yield QTLs, 6 marker intervals were found to have QTLs conferring biomass and apparent harvest index, which implied a partially common genetic basis among the three traits.

Key words: Soybean, Biomass accumulation, Apparent harvest index, Yield, QTL analysis