| Soybean is an important cash crop and is widely cultivated in our country.The spring soybean producing area in northern China is an important soybean producing area,which usually suffers from low temperature and drought and other adverse conditions during the sowing period.The developed root system of soybean varieties at the seedling stage can promote the whole seedling in the field to form strong mature plants and obtain higher yield.In this study,326 natural populations of northern spring soybean cultivars were used as materials.Seven root traits of soybean seedlings were measured under sand culture and hydroculture.Membership function was used to grade root traits,and markers of control roots were obtained,which provided theoretical basis for molecular assisted breeding.The results are analyzed as follows:1.Phenotypic variation under different conditionsUnder sand culture and water culture,the seven root characters were normally distributed.The genetic variation coefficients of root traits were inconsistent under sand culture and hydroculture.The genetic variation coefficients of 7 characters under sand culture were 9.29%-46.10%,and the variation coefficients of taproot length were the largest.The coefficient of genetic variation of 7 characters was 11.58%-37.54%under hydroponics,and the coefficient of variation of total root length was the largest.There was a significant correlation among the seven traits under sand culture condition.Under hydroponic condition,except root volume and mean diameter,the other 6 characters were highly significantly correlated.2.Determination of root system of soybean resourcesThe root growth status was divided into 5 levels by membership function.The roots of two varieties under different conditions and developed varieties were different.The soybean varieties with highly developed roots under sand culture condition were Anda Baimei,Huang Omphalou,Yiwo Liang,Nenfeng 10 and Tiefeng 8.Under hydroponic condition,the soybean varieties with highly developed root system were 164-4-19,bus 6309-2 and Mufeng 4.3.Correlation results between root traits and SNP markersThe results of linkage disequilibrium show that the minimum attenuation distance of population is 433kb.The population structure was divided into 7 subgroups.The mixed linear model was used for association analysis.Under sand culture condition,with-log10P≥5 as the significance threshold,208 SNP marker sites were detected to be associated with 7 root traits,and the variation of phenotypic variation rate of single SNP marker sites ranged from 6.39%to 10.67%.A total of 11 SNP markers were associated with 2 or 3 traits.ss715581248(Gm2),ss715585152(Gm3),ss715595638(Gm6),ss715605658(Gm10),ss715605709(Gm10),ss715613211(Gm12),ss715613903(GM10)Gm13),ss715630090(Gm14),ss715604372(Gm9),ss715606026(Gm10),ss715 632582(Gm 18).Under hydroponics,with-log10P≥4 as the significance threshold,a total of 44 SNP marker sites were detected to be associated with 7 root traits,and the phenotypic contribution rate of a single SNP marker site varied from 5.36%to 8.82%,among which 4 SNP marker sites were associated with 2 traits.They are ss715585464(Gm3),ss715585463(Gm3),ss715610695(Gm11),and ss715610678(Gm11).At the same time,ss715599984(Gm8)and ss715634986(Gm19)were associated with different traits in sand culture and hydroculture.4.A total of 9 same SNP marker sites were associated under the two breeding conditions,and 7 candidate genes were excavated around them,which were distributed on chromosomes 8 and 19.The results of gene annotation indicated that these genes may promote root growth,stress resistance and trace element transport in soybean roots.This study,together with the identification of soybean seedling root traits under different conditions,SNP site screening and gene annotation,can provide theoretical basis for subsequent studies on soybean root growth and development. |
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