Study On Changes Of Plant Type And The Relationship With Yield Of Soybean Cultivars With Genetic Improvement Of Release In Jilin Province

Yield of soybean was improved significantly because of genetic improvement. Our objective in the study was to examine changes of soybean plant type and genetic relationship between yield and plant type associated with 30 soybean cultivars of 82 years applied in the production at Jilin province.All the tested cultivars were grown in the same field of Jilin Agricultural University in 2005 and 2006 and the genetic improvement characteristics of soybean yield and its components, traits of plant type were measured. In order to offer reliable theory for breeding and cultivating, the documents were analyzed. The main experimental results show that:(1) Yield of soybean in Jilin province was 1212.77kg·hm^-2in 1923,nevertheiess, in 2005 the yield have reached 2275.82kg·hm^-2. Yield was improved by proximately 87.65% from 1923 to 2005 and was increased by proximately 1.06% per year.Pods per plant, seeds per plant and 100-weight were increased with year of release. There were obvious difference in new cultivars and old cultivars, moreover, the tendency of pods per plant, seeds per plant and 100-weight among soybean cultivars at different canopy was that upper and middle level were bigger and lower was smaller.As for number of pods, new cultivars were more than old cultivars in the whole canopy, lower level specially. Blighted pods and 1,2 seeded pods of new cultivars were less than old cultivars, nevertheless, 3 and 4 seeded pods of new cultivars were more than old cultivars.(2)There was a positive association between leaf area per plant and year of release significantly, nevertheless, there was a negative association between leaflet area and year of release and length/width ratio was increased with year of release at the R₂, R₄, and R₆ of stages individually.Number of leaves was increased with year of release. The results of leaf area per plant were shown that: new cultivars>middle cultivars>old cultivars. The canopies of old cultivars took the shape of the umbrella, while the canopies of modern cultivars took the shape of the pagoda.The length of petiole was increased with year of release. The changes of old cultivars petiole were not obvious, however, the petiole of new cultivars changed obviously, namely: upper level>middle level>lower level.(3) LAI was increased with year of release significantly and the changes of LAI were the same in the whole growth stages, with progress of growth, LAI of new cultivars was lager than old cultivars significantly. MYA of old cultivars were not changed obviously, but MYA of new cultivars were changed significantly, namely: upper level>middle level>lower level, the whole canopy took the shape of pagoda.(4)Stem diameter was increased with year of release; lodging tolerance was improved over time in soybean cultivars in this study. The stem diameter of new cultivars was the same as old cultivars at R₂ stages, with development of growth, stem diameter of new cultivars was bigger than old cultivars after R₃ stages obviously. Lodging score was reduced with year of release and reduced by49.98% from 1923 to 2005, moreover, plant height reduce with increase of branches and nodes. The tolerance of resistance lodging of new cultivars was better than old cultivars.(5)Content of seed oil was increase by accompanied of reduce of content of seed protein with year of release. content of seed oil was improved 6.69% from 1923 to 2005 and was increased by 0.08% per annual year, nevertheless, content of seed protein was reduced 4.49% from 1923 to 2005 and was reduced 0.05% annual year. Tendency of oil/protein ratio was tendency of oil content with year of release.In all, the results in this study show that:(1) With year of release, days to maturity of soybean became shorter and shorter and number of nodes was increased by accompanied of reduce of plant height and number of branches, moreover, lodging score was reduced with increase of stem diameter.(2) The length of petiole was increased with year of release. The changes of old cultivars petiole were not obvious, however, the petiole of new cultivars changed obviously, namely: upper level>middle level>lower level.(3) Leaf area and LAI were increased with year of release, the canopies of old cultivars took the shape of the umbrella, while the canopies of modern cultivars took the shape of the pagoda. MYA of old cultivars was not changed obviously, thus, MYA of new cultivars was changed significantly, upper leaf grew toward up, plant type of new cultivars was better than old cultivars. Plant type of soybean was improved well with progress of genetic improvement and the excellent plant type has resolved the problem of brightness and wind in soybean canopy. For all this, yield of soybean was improved significantly with year of release and number of 3,4 seeded pods was increased obviously. Though the analysis of correlation coefficients, there was relevance between yield and plant height, lodging scores, stem diameter, leaf area per plant, LAI, number of pods per plant, 3 seeded pods, 4 seeded pods significantly and we think that these traits were reliable in the course of selecting high-yield cultivars.