The Temperature Sensitivity In Flowering Time Among Different Ecotypes Of Soybean And Associated Loci

Temperature plays a vital role in soybean growth and development.There are different signal pathways and regulation mechanisms that respond to temperature in soybean.Different ecotypes of soybean have different responses to temperature and photothermal interaction effect.The flowering time of soybean is not only affected by environment,but also regulated by genes,and the locus effects related to flowering time are distinct under different photothermal conditions.In this study,temperature sensitivity of different ecotypes of soybean was evaluated,temperature sensitive sites were explored by association analysis and the effects of key sites were identified.1.In 2017 and 2018,temperature sensitivity of different ecotypes soybean varieties was studied,four photoperiod and temperature environments including long day and low temperature,short day and low temperature,long day and high temperature,short day and high temperature were designed by sowing in different seasons and artificially controlling photoperiod.The thermal time before flowering of different soybean ecotypes varieties follows the order:southern summer-sowing soybean,southern spring-sowing soybean,Huang-Huai-Hai summer-sowing soybean,Huang-huai-hai spring-sowing soybean,northern spring-sowing soybean.The relationship between thermal time and maturity group was exponential curve.2.The temperature sensitivity of different soybean ecotypes varieties was as follows:southern summer-sowing soybean,southern spring-sowing soybean,northern spring-sowing soybean,Huang-Huai-Hai summer-sowing soybean,Huanghuahai spring-sowing soybean.The temperature sensitivity decreased with the increasing of maturity group.The temperature sensitivity value(TRS%)was used as the evaluation criterion of dividing the tested materials into five temperature sensitivity grades,and temperature insensitive and sensitive varieties were screened.The results showed that 5varieties were insensitive to temperature,5 varieties were sensitive to temperature,while most of the other varieties were middle type.The interaction effect was significantly various among different ecotypes of soybeans,the photothermal interaction of Huang-Huai-Hai spring-sowing soybean was the strongest,however interaction of southern summer-sowing soybean was the weakest.3.Population structure,kinship and LD analysis:9029 SNPs of tested materials was used,population structure,principal component analysis and NJ cluster analysis showed that the population was divided into two subgroups.In this natural population,about 72.19%kinship between any two lines was less than 0.1,indicating that the genetic relationship between the natural population was far from each other,which has little effect on the association analysis results.The mean linkage disequilibrium distance of population was calculated by r~2 value,which was 130.54kb.4.Association analysis of flowering date and temperature sensitivity traits in different environments.A total of 44 significant loci were detected,25 SNPs were related to the days of flowering,and 19 SNPs were related to temperature sensitivity.There were significant differences in flowering time of different alleles in different photothermal conditions.24 flowering-related candidate genes were screened in the LD region of the significant loci.Seven significant loci were detected in multiple environments,and there were flowering related candidate genes E2,GmCEN1,GmCEN4,GmBFT,GLYMA17G231600,GLYMA19G217900 and E3.According to SNP,each candidate genes were divided into different haplotypes according to the base differences.It was found that the ecotypes of different haplotypes were distributed regularly.Moreover,there were significant differences in flowering time and temperature sensitivity of different haplotypes.