Correlation Analysis Of Soybean Apical Hook Formatio

Soybean is one of the important oil crops in China and has high nutritional and economic value.As a dicotyledonous plant,the seeds emerge from the ground with the tip of the hypocotyl bent downward to form a hook-like structure,known as the apical crook.This is to avoid possible mechanical damage to the seedlings during their emergence from the soil.The process of establishment and unfolding of the apical arc is also a transition from dark to light form,during which the fragile apical meristem and cotyledons may be damaged if the apical arc is not established in time;If the top hooks are not opened in time after the seedlings emerge,it will affect the establishment of plant photomorphology and then affect the plant’s seedling establishment and strength.Existing studies have shown that there are complex molecular regulatory mechanisms involved in the establishment and opening of the apical curvature,which are mainly regulated by various plant growth hormones such as growth hormone,ethylene,gibberellin and environmental signals.Therefore,the use of association analysis to investigate the genetic characteristics of the apical crook trait in soybean can provide some theoretical basis for the development of molecular marker-assisted breeding,which is important for improving the seedling establishment rate and yield of soybean in the field.In this study,two natural populations consisting of 329 and 192 soybean germplasm resources were selected as test materials for 4 apical curvature data of soybean seedling apical curvature angle(two different periods),curvature unfolding rate and curvature unfolding rate as phenotypic traits.Association analysis was performed to locate relevant significant loci by combining the information of 30,558 SNP markers.The main results are as follows:1.Genetic diversity analysis of bent traits in soybean populations showed that: The coefficient of genetic variation for the 4 apical curvature traits ranged from 9.69% to30.56%,with a wide range of genetic variation among the different traits;The correlation among the 4 apical curvature traits was high and all were significantly or highly significantly correlated.2.Correlation analysis of soybean seedling vigor traits: The correlation analysis of4 apical curvature traits with 4 apical curvature traits of seedling height,seedling weight,hypocotyl length and primary root length of soybean was conducted in a population of50 randomly selected soybean varieties.The results showed that the traits associated with apical curvature were significantly correlated with the growth and development of above-ground parts of soybean seedlings,the growth correlation with the root system is highly influenced by external influences.3.Markers significantly associated with four apical curvature traits: A total of 61 SNP markers significantly associated loci were detected in 329 soybean populations,it is mainly distributed on sixteen chromosomes of soybean except chromosomes 1,3,10 and 12,phenotypic variation explained by 4.37%-7.11%.The four markers with the highest contribution weress715592860(HA1),ss715602880(HA2),ss715636688(HDR),ss715632391(HER).30 SNP markers were detected in 192 soybean populations with significantly associated loci,distributed on chromosomes 4,5,8,11,13,14,and 18 of soybean,phenotypic variation explained by 6.08%-11.42%,the four markers with the highest contribution were ss715602849(HA1),ss715589702(HA2),ss715588919(HDR),and ss715590242(HER).A total of 17 markers were associated to the same marker at the same time for different traits.There were 8 regions that were co-associated to between the two groups.4.Functional annotation of genes localized to significant intervals,A total of 10 candidate genes associated with the apical crook trait in soybean were screened,The seven genes,Glyma.06g147600,Glyma.13g145700,Glyma.08g025600,Glyma.08g145300,Glyma.13g030900,Glyma.19g130400,Glyma.18g287200,play a role in the signaling process of oleuropein endolipid,abscisic acid,ethylene,growth hormone,jasmonic acid,salicylic acid and other plant growth hormone signaling processes;The three genes Glyma.08g145600,Glyma.13g030700 and Glyma.11g189600 play a role in the elongation of plant cell growth.