Screening Of High-Yield Summer Soybean Varieties And Analysis Of Yield Formation Regulation

As an important oil cash crop in China,soybean production is generally low,far from meeting the demand,and is heavily dependent on imports.The trend of Sichuan soybean industry is the same as the general trend of the whole country,with supply exceeding demand,so there is an urgent need to select high-yield soybean varieties suitable for Sichuan area.Therefore,in this study,the biomass(R6)and yield(R8)of Nanxiadou 25,the control variety of soybean experiment in Sichuan Province in the past two years,were taken as reference to preliminarily screen the high-yield summer soybean varieties suitable for planting in Sichuan,and the summer soybean varieties from different ecological regions were classified,and representative soybean varieties were selected from each type.This paper studied and analyzed the yield and yield component factors of soybean,photosynthetic physiological index,dry matter accumulation and transport,compared and analyzed the differences in yield formation of various types of soybean,preliminarily explained the characteristics of high-yield soybean varieties,and provided theoretical basis for breeding high-yield summer soybean.The main research results are as follows:(1)Based on the biomass and yield of Nanxiadou 25 in 2020 and 2021,117 summer soybean varieties from different ecological regions were divided into four types: High yield and low biomass soybean(HL),high yield and high biomass soybean(HH),low yield and low biomass soybean(LL)and low yield and high biomass soybean(LH),including 17 copies of HL,43 copies of HH,21 copies of LL and 36 copies of LH from 2020;there were58 copies of HL,34 copies of HH,10 copies of LL and 15 copies of LH from 2021,and a total of 19 materials with stable performance in two years,including 13 high-yield soybeans and 6 low-yield soybeans.(2)The yield of high-yielding soybean was significantly higher than that of lowyielding soybean.Pod number per plant and grain weight per plant of high-yielding soybean were significantly higher than those of low-yielding soybean,while grain number per plant of high-yielding soybean was higher than that of low-yielding soybean,but the difference was not significant.There was no obvious rule in the difference of agronomic characters between high yield soybean and low yield soybean.(3)There were differences in leaf photosynthetic physiology among different soybean varieties.The leaf area index of high-yielding soybean was significantly higher than LL and lower than LH.The net photosynthetic rate of high-yield soybean was significantly higher than that of low-yield soybean.The soil and plant analyser deflowerment,maximal photochemical efficiency of PSⅡ(Fv/Fm),actual photochemical efficiency of PSⅡ(Y(Ⅱ)),electron transfer rate(ETR)and photochemical quenching(qp)were higher than those of low-yield soybean,but the non-photochemical quenching(NPQ)was significantly lower than that of low-yield soybean.The photosynthetic performance of high-yield soybean is better.At the same yield level,the difference of high yield soybean biomass was due to the fact that the ETR of HH was higher than that of HL,but the NPQ was lower than that of HL.However,the reason for the difference in biomass between the two types of low-yielding soybeans was that the leaf area index,soil and plant analyser deflowerment and net photosynthetic rate of LH were higher than those of LL.(4)There were differences in dry matter accumulation,transport and distribution capacity among different soybean varieties.The percentage of leaf of high-yielding soybean at R2 stage was higher than that of low-yielding soybean,and the percentage of pod of harvesting organ of high-yielding soybean was higher than that of low-yielding soybean from the beginning of pod setting at R4 stage to maturity at R8 stage.(5)The carbon metabolism indexes of different soybean varieties were different.The activities of carbon metabolizing enzymes and the contents of sucrose and fructose in R2 stage of high-yielding soybean were higher than those in low-yielding soybean,so the sucrose metabolism of high-yielding soybean was more active.In R6 stage,the sucrose content in high-yielding soybean leaves was significantly higher than LL,but significantly lower than LH,showing the same trend as sucrose phosphate synthases(SPS).However,the fructopyranose content in high-yielding soybean pods was significantly higher than that of LL and LH,showing the same trend as sucrose synthases activity(SS).In summary,the high-yielding soybean had a stronger ability to transport and distribute sucrose.