Changes Of Source-Sink Relationship With Genetic Improvement Of Soybean Cultivars In Jilin Province

Soybean grain yield is the product of accumulating dry matter(source) and allocating portion of the total aboveground biomass to grain(sink).The relationship of source and sink was reported very much.Past research has focused on morphological traits and changes of source and sink of soybean extensively.However, research of soybean genetic improvement has been hardly reported in present.Our objective was to investigate the changes in relationships of source and sink and yield increase in the selection of historical cultivars using 30 soybean cultivars cultivated and genetically improved from 1923 to 2005,in order to offer to new foundation for breeders.The experiments were performed with randomized complete block design with at least three replicates in Changchun(43.53°N,125.10°E),Jilin Province in 2006-2007.Leaf area per plant,net photosynthetic rate,chlorophyll content,SLW and LAI at V₄,R₂,R₄,R₆ growth stages,measured the yield after harvest,the number of pods and seed per plant,weight of pod and seed per plant and so on.The main experimental results were as follow:1 changes of soybean yield in genetic improvement in Jilin ProvinceYield of soybean in Jilin province was increased by 92.48%(1.13%per year) from 1923 to 2005;Days to maturity were shortened by 13.8 days,the results indicated that the short-season soybean cultivars were cheese by breeders.2 changes of source capacity and sink capacity in genetic improvementSoybean grain yield is the product of accumulating dry matter(source) and allocating portion of the total aboveground biomass to grain(sink).Leaf assimilation capacity(leaf area,leaf net photosynthesis rate,leaf area index,specific leaf weight and chlorophyll content) of soybean released of year was improved in genetic improvement.But,source capacity is smaller than sink capacity(i.e.pods weight per plant,number of pods per plant,number of 3-seed pods,number of 4-seed pods,number of seed per plant and seeds weight per pant) in genetic improvement.The same time,pods of no seeds were increased 196%(2.40%per year) from 1923 to 2005 significantly.3 changes in relationships of source and sink in genetic improvement in Jilin ProvinceR₄ stage is the max leaf area of soybean,Pods weight per unit leaf area,seeds weight per unit leaf area and numbers of seed per unit leaf area increased with year of released,they increased of 34.80%,77.07%and 25.32%(0.42%,0.94%and 0.31%per year) from 1923 to 2005,respectively.Furthermore,the study showed that source capacity was improved lowlier than sink capacity and there was inordinate between source and sink. Capacity of source and sink of soybean increased with increase of yield,improvement of sink was faster than source.For this reason,pods of no seed increased with year of released.Because large of leaf area were influence on canopy structure,better canopy,high photosynthesis ability and chlorophyll content and high specific leaf weight can give breeder to help in the future of breeding work.